Gestational Weight Gain
Implications of an Antenatal Lifestyle Intervention
to Cornelis and Hampus Örebro Studies in Medicine 146
ANN-KRISTIN RÖNNBERG
Gestational Weight Gain
Implications of an Antenatal Lifestyle Intervention
to Cornelis and Hampus Örebro Studies in Medicine 146
ANN-KRISTIN RÖNNBERG
Gestational Weight Gain
Implications of an Antenatal Lifestyle Intervention
© Ann-Kristin Rönnberg, 2016
Title: Gestational Weight Gain. Implications of an Antenatal Lifestyle Intervention. Publisher: Örebro University 2016
www.oru.se/publikationer-avhandlingar
Print: Örebro University, Repro 08/2016 ISSN 1652-4063
ISBN 978-91-7529-148-2
Abstract
Ann-Kristin Rönnberg (2016): Gestational Weight Gain. Implications of an Antenatal Lifestyle Intervention. Örebro studies in Medicine 146.
Background: Excessive gestational weight gain (GWG) is common in developed countries and is associated with an increased risk of maternal and offspring morbidity.
Evidence regarding efficacy and safety of antenatal lifestyle intervention is limited in terms of both systematic reviews and original trials. This thesis is based on the need to further explore this research area. Objectives: To assess and grade current evi- dence and evaluate short and long-term effects of an antenatal lifestyle intervention on women and their offspring Materials: Controlled trials of intervention published before August 2009 were systematically searched and reviewed. A randomized con- trolled trial (RCT) including 445 healthy women aged >18 years with a body mass index (BMI) ≥19 and ≤16 weeks pregnant and their offspring was performed during 2007-2015 in Örebro Region, Sweden. Methods: The Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system was used for review.
Our RCT (called the VIGA trial) compared standard care with a composite interven- tion consisting of education, application of a personalized weight graph, prescription of exercise and more frequent monitoring of weight. Standardized measures of weight and height in offspring waere analysed based on World Health Organization (WHO) Child Growth Standards. Results: Quality of evidence across the studies published pre-August 2009 was concluded to be very low. Our intervention significantly re- duced mean GWG (kg) but the proportion of women with excessive GWG, according to recommendations, was not significantly reduced. Short- term postpartum weight retention (PPWR) was significantly lower after the intervention but no significant difference remained 1 year after delivery. Offspring mean BMI z-scores or proportion of obesity did not differ between study groups at either birth or age 5. Conclusions:
The antenatal lifestyle intervention reduced mean GWG and short-term PPWR but no long-term effects on maternal weight retention or offspring obesity were seen.
Alternative modes and timing of intervention should be considered in future research.
Reducing the prevalence of pre-conception obesity must still be considered the pri- mary means to improve maternal and fetal outcome.
Keywords: Gestational weight gain, maternal health, pregnancy, prevention of obesi- ty, lifestyle intervention, childhood obesity.
Ann-Kristin Rönnberg, School of Health and Medical Sciences, Örebro University,
SE-701 82 Örebro, Sweden, ann-kristin.ronnberg@regionorebrolan.se
© Ann-Kristin Rönnberg, 2016
Title: Gestational Weight Gain. Implications of an Antenatal Lifestyle Intervention. Publisher: Örebro University 2016
www.oru.se/publikationer-avhandlingar
Print: Örebro University, Repro 08/2016 ISSN 1652-4063
ISBN 978-91-7529-148-2
Abstract
Ann-Kristin Rönnberg (2016): Gestational Weight Gain. Implications of an Antenatal Lifestyle Intervention. Örebro studies in Medicine 146.
Background: Excessive gestational weight gain (GWG) is common in developed countries and is associated with an increased risk of maternal and offspring morbidity.
Evidence regarding efficacy and safety of antenatal lifestyle intervention is limited in terms of both systematic reviews and original trials. This thesis is based on the need to further explore this research area. Objectives: To assess and grade current evi- dence and evaluate short and long-term effects of an antenatal lifestyle intervention on women and their offspring Materials: Controlled trials of intervention published before August 2009 were systematically searched and reviewed. A randomized con- trolled trial (RCT) including 445 healthy women aged >18 years with a body mass index (BMI) ≥19 and ≤16 weeks pregnant and their offspring was performed during 2007-2015 in Örebro Region, Sweden. Methods: The Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system was used for review.
Our RCT (called the VIGA trial) compared standard care with a composite interven- tion consisting of education, application of a personalized weight graph, prescription of exercise and more frequent monitoring of weight. Standardized measures of weight and height in offspring waere analysed based on World Health Organization (WHO) Child Growth Standards. Results: Quality of evidence across the studies published pre-August 2009 was concluded to be very low. Our intervention significantly re- duced mean GWG (kg) but the proportion of women with excessive GWG, according to recommendations, was not significantly reduced. Short- term postpartum weight retention (PPWR) was significantly lower after the intervention but no significant difference remained 1 year after delivery. Offspring mean BMI z-scores or proportion of obesity did not differ between study groups at either birth or age 5. Conclusions:
The antenatal lifestyle intervention reduced mean GWG and short-term PPWR but no long-term effects on maternal weight retention or offspring obesity were seen.
Alternative modes and timing of intervention should be considered in future research.
Reducing the prevalence of pre-conception obesity must still be considered the pri- mary means to improve maternal and fetal outcome.
Keywords: Gestational weight gain, maternal health, pregnancy, prevention of obesi- ty, lifestyle intervention, childhood obesity.
Ann-Kristin Rönnberg, School of Health and Medical Sciences, Örebro University,
SE-701 82 Örebro, Sweden, ann-kristin.ronnberg@regionorebrolan.se
TABLE OF CONTENTS
INTRODUCTION ...11
BACKGROUND ...14
Composition and timing of weight gain during pregnancy ...14
Gestational weight gain from a Swedish perspective ...15
Long-term maternal effects ...19
Trans-generational effects ...20
Lifestyle intervention in relation to pregnancy ...21
Reviewing scientific evidence – the GRADE system ...22
ETHICAL CONSIDERATIONS ...24
AIMS...25
MATERIALS AND METHODS ...26
Paper I ...26
Papers II-IV ...27
Intervention ...27
Randomization ...29
Statistical methods, Papers II-IV ...29
Sample size ...30
Child Growth Standards applied in Paper IV ...30
RESULTS ...31
Paper I ...31
Conclusion Paper I ...34
Paper II ...34
Conclusion Paper II ...37
Paper III ...37
Conclusion Paper III ...40
Paper IV ...41
Conclusion Paper IV ...45
DISCUSSION ...46
Summary of main findings ...46
Strength and limitations of included studies ...46
Interpretation and implications of study results ...48
Future research recommendations ...50
CONCLUSION ...51
ACKNOWLEDGEMENTS ...52
LIST OF PUBLICATIONS
I Ronnberg AK, Nilsson K. Interventions during pregnancy to reduce exces- sive gestational weight gain: a systematic review assessing current clinical evidence using the Grading of Recommendations, Assessment, Develop- ment and Evaluation (GRADE) system. BJOG 2010; 117:1327–1334.
II Ronnberg AK, Ostlund I, Fadl H, Gottvall T, Nilsson K. Intervention during pregnancy to reduce excessive gestational weight gain — a ran- domised controlled trial. BJOG 2014; DOI: 10.1111/1471-0528.13131.
III Ronnberg AK, Hanson U, Ostlund I, Nilsson K. Effects on postpartum weight retention after antenatal lifestyle intervention – a secondary anal- ysis from a randomized controlled trial. AOGS 2016; DOI: 10.1111/
aogs.12910.
IV Ronnberg AK, Hanson U, Nilsson K. Effects of an antenatal lifestyle in- tervention on childhood obesity – a five year follow-up of a randomised controlled trial. Submitted
All previously published papers were reproduced with permission
from the publishers.
TABLE OF CONTENTS
INTRODUCTION ...11
BACKGROUND ...14
Composition and timing of weight gain during pregnancy ...14
Gestational weight gain from a Swedish perspective ...15
Long-term maternal effects ...19
Trans-generational effects ...20
Lifestyle intervention in relation to pregnancy ...21
Reviewing scientific evidence – the GRADE system ...22
ETHICAL CONSIDERATIONS ...24
AIMS...25
MATERIALS AND METHODS ...26
Paper I ...26
Papers II-IV ...27
Intervention ...27
Randomization ...29
Statistical methods, Papers II-IV ...29
Sample size ...30
Child Growth Standards applied in Paper IV ...30
RESULTS ...31
Paper I ...31
Conclusion Paper I ...34
Paper II ...34
Conclusion Paper II ...37
Paper III ...37
Conclusion Paper III ...40
Paper IV ...41
Conclusion Paper IV ...45
DISCUSSION ...46
Summary of main findings ...46
Strength and limitations of included studies ...46
Interpretation and implications of study results ...48
Future research recommendations ...50
CONCLUSION ...51
ACKNOWLEDGEMENTS ...52
LIST OF PUBLICATIONS
I Ronnberg AK, Nilsson K. Interventions during pregnancy to reduce exces- sive gestational weight gain: a systematic review assessing current clinical evidence using the Grading of Recommendations, Assessment, Develop- ment and Evaluation (GRADE) system. BJOG 2010; 117:1327–1334.
II Ronnberg AK, Ostlund I, Fadl H, Gottvall T, Nilsson K. Intervention during pregnancy to reduce excessive gestational weight gain — a ran- domised controlled trial. BJOG 2014; DOI: 10.1111/1471-0528.13131.
III Ronnberg AK, Hanson U, Ostlund I, Nilsson K. Effects on postpartum weight retention after antenatal lifestyle intervention – a secondary anal- ysis from a randomized controlled trial. AOGS 2016; DOI: 10.1111/
aogs.12910.
IV Ronnberg AK, Hanson U, Nilsson K. Effects of an antenatal lifestyle in- tervention on childhood obesity – a five year follow-up of a randomised controlled trial. Submitted
All previously published papers were reproduced with permission
from the publishers.
ABBREVIATIONS
AGA Appropriate for gestational age
BMI Body mass index
CI Confidence interval
CS Caesarean section
FaR Fysisk aktivitet på recept
(Akronym for prescribed physical activity in Swedish) FBW Fetal birth weight
GDM Gestational diabetes mellitus GWG Gestational weight gain HT Hypertension
IOM Institute of Medicine LGA Large for gestational age LMP Last menstrual period
OR Odds ratio
PE Preeclampsia
PHT Pregnancy induced hypertension
PP Postpartum
PPWR Postpartum weight retention SGA Small for gestational age
SD Standard deviation
VIGA Vikt Intervention under Graviditet (Trial akronym in Swedish) WHO World Health Organization
REFERENCES ...54 SUMMARY IN SWEDISH
SAMMANFATTNING PÅ SVENSKA ...60
Viktökning under graviditet (VIGA) ...60
APPENDIX ...62
ABBREVIATIONS
AGA Appropriate for gestational age
BMI Body mass index
CI Confidence interval
CS Caesarean section
FaR Fysisk aktivitet på recept
(Akronym for prescribed physical activity in Swedish) FBW Fetal birth weight
GDM Gestational diabetes mellitus GWG Gestational weight gain HT Hypertension
IOM Institute of Medicine LGA Large for gestational age LMP Last menstrual period
OR Odds ratio
PE Preeclampsia
PHT Pregnancy induced hypertension
PP Postpartum
PPWR Postpartum weight retention SGA Small for gestational age
SD Standard deviation
VIGA Vikt Intervention under Graviditet (Trial akronym in Swedish) WHO World Health Organization
REFERENCES ...54 SUMMARY IN SWEDISH
SAMMANFATTNING PÅ SVENSKA ...60
Viktökning under graviditet (VIGA) ...60
APPENDIX ...62
The first measured weight in pregnancy if first visit occurred at <16 weeks of pregnancy according to LMP or early ultrasound dating.
DEFINITIONS
Pre-pregnancy weight
Gestational weight gain Bodyweight at delivery minus bodyweight at
<16 w of pregnancy.
Postpartum weight retention Bodyweight at postpartum visit minus bodyweight at <16 w of pregnancy.
Preterm delivery Birth < 37 weeks’ gestation.
Perinatal mortality Stillbirths and deaths during the first seven days postpartum independent of gestational age.
INTRODUCTION
Excessive weight gain during pregnancy is common in developed countries and has been linked to an increased risk of complications during pregnancy, delivery and the postpartum period for both mother and child. High gestational weight gain (GWG) is primarily linked to morbidity associated with high fetal birth weight (FBW) (1) but women with excessive GWG are also more likely to have high postpartum weight retention (PPWR) (2) and their offspring have been reported to have an increased risk of becoming overweight or obese (3, 4). An effective intervention in maternal health care aimed at avoiding or limiting excessive GWG, could theoretically improve not only obstetric outcome but also long term-health in mother and child by reducing the risk of developing obesity.
The maternal and fetal risk associated with excessive weight gain however, has to be balanced against the risk associated with inadequate GWG. Low GWG or ges- tational weight loss (GWL) has been linked to negative obstetric outcome such as preterm birth, fetal growth restriction, and failure to initiate breast-feeding as well as increased infant mortality (5-7).
Maternal pre-pregnancy BMI modifies the association between GWG and many of these health outcomes (Figure 1) so that determining the optimal range of GWG for women in different BMI categories, balancing the risks associated with low and high gain for mother and child, has proved to be a challenge. In 1990 the Institute of Medicine (IOM) issued the first evidence-based guidelines for GWG in relation to maternal pre-pregnancy BMI. Primarily it was concern for women with pre-pregnan- cy underweight and low GWG that spurred the creation of the first IOM guidelines (8). Promted by an increased prevalence of overweight and obesity in women of re- productive age and the observation that an increasing number of women were gaining excessively during pregnancy, the IOM reconvened and revised their guidelines in 2009, adding an upper limit for GWG in women with pre-pregnancy obesity and at the same time adopting the World Health Organization (WHO) classifications for BMI (9) (Table 1).
BMI GWG (kg) Mean rate of GWG (kg/week) 2nd and 3rd trimester
<18.5 12.5-18 0.51
18.5-24.9 11.5-16 0.51
25-29.9 7-11.5 0.28
>30 5-9 0.22
Table 1. Institute of Medicine (IOM) recommendations of 2009 for gestational weight gain (GWG) based on maternal pre-pregnancy body mass index (BMI).
The first measured weight in pregnancy if first visit occurred at <16 weeks of pregnancy according to LMP or early ultrasound dating.
DEFINITIONS
Pre-pregnancy weight
Gestational weight gain Bodyweight at delivery minus bodyweight at
<16 w of pregnancy.
Postpartum weight retention Bodyweight at postpartum visit minus bodyweight at <16 w of pregnancy.
Preterm delivery Birth < 37 weeks’ gestation.
Perinatal mortality Stillbirths and deaths during the first seven days postpartum independent of gestational age.
INTRODUCTION
Excessive weight gain during pregnancy is common in developed countries and has been linked to an increased risk of complications during pregnancy, delivery and the postpartum period for both mother and child. High gestational weight gain (GWG) is primarily linked to morbidity associated with high fetal birth weight (FBW) (1) but women with excessive GWG are also more likely to have high postpartum weight retention (PPWR) (2) and their offspring have been reported to have an increased risk of becoming overweight or obese (3, 4). An effective intervention in maternal health care aimed at avoiding or limiting excessive GWG, could theoretically improve not only obstetric outcome but also long term-health in mother and child by reducing the risk of developing obesity.
The maternal and fetal risk associated with excessive weight gain however, has to be balanced against the risk associated with inadequate GWG. Low GWG or ges- tational weight loss (GWL) has been linked to negative obstetric outcome such as preterm birth, fetal growth restriction, and failure to initiate breast-feeding as well as increased infant mortality (5-7).
Maternal pre-pregnancy BMI modifies the association between GWG and many of these health outcomes (Figure 1) so that determining the optimal range of GWG for women in different BMI categories, balancing the risks associated with low and high gain for mother and child, has proved to be a challenge. In 1990 the Institute of Medicine (IOM) issued the first evidence-based guidelines for GWG in relation to maternal pre-pregnancy BMI. Primarily it was concern for women with pre-pregnan- cy underweight and low GWG that spurred the creation of the first IOM guidelines (8). Promted by an increased prevalence of overweight and obesity in women of re- productive age and the observation that an increasing number of women were gaining excessively during pregnancy, the IOM reconvened and revised their guidelines in 2009, adding an upper limit for GWG in women with pre-pregnancy obesity and at the same time adopting the World Health Organization (WHO) classifications for BMI (9) (Table 1).
BMI GWG (kg) Mean rate of GWG (kg/week) 2nd and 3rd trimester
<18.5 12.5-18 0.51
18.5-24.9 11.5-16 0.51
25-29.9 7-11.5 0.28
>30 5-9 0.22
Table 1. Institute of Medicine (IOM) recommendations of 2009 for gestational weight gain (GWG) based on maternal pre-pregnancy body mass index (BMI).
Gestational weight gain (GWG) within IOM ranges was consistently associated with good maternal and fetal outcomes. Evidence at the time was judged inadequate to provide specific guidelines by grade of obesity or to support recommendations on GWG < 5 kg or gestational weight loss (GWL) for obese wome
Normal Weight
0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg
Underweight
0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg
Absolute Adjusted Risk
Small-for-gestational-age Large-for-gestational-age Emergency caesarean delivery Postpartum weightretention
0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg
Obese
0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg
0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg 0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg 0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg 0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg 0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg
Small-for-gestational-age Large-for-gestational-age Emergency caesarean delivery Postpartum weightretention Small-for-gestational-age Large-for-gestational-age Emergency Cesarean Delivery Postpartum Weight Retention Overweight
0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg 0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg 0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg 0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg 0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg
Extremely Obese
0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg 0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg
Gestational Weight Gain
Absolute Adjusted RiskAbsolute Adjusted Risk
Gestational Weight Gain
Gestational Weight Gain Gestational Weight Gain
Gestational Weight Gain
≥
≥ ≥
≥
≥
Figure 1. Gestational weight gain (GWG)-specific absolute risks for fetal and maternal outcome based on pre-pregnancy body mass index (BMI) (Weight gain during pregnancy:
reexamining the guidelines. Washington, DC: National Academies Press; 2009, Appendix G, Reprinted with permission from publisher) (10).
Observational studies have continued to provide ambiguous results on the subject.
Several large population-based cohort studies published after the release of the IOM guidelines considered it safe to set more restrictive weight gain limitations for obese women (11-14). A systematic review published in 2010 states that overweight and obese women who gain less weight than the ranges recommended by the IOM do not have an increased risk of having a low birth weight infant (15). Other researchers have argued that even the present IOM recommendations may be too restrictive for severely obese women and may be associated with increased rates of preterm births, small-for-gestational-age (SGA) infants and perinatal mortality (7). Future studies may provide sufficient evidence to lead to customized recommendations on GWG in relation not only to grade of pre-pregnancy obesity but also to individual maternal metabolic status and genetic disposition for obesity.
An increasing awareness among obstetricians about the high prevalence of exces-
sive GWG among Swedish women and the growing base of evidence regarding asso-
ciations with negative short-term and long-term maternal and fetal outcome prompted
this thesis which encompasses research in the field of antenatal lifestyle intervention
with the aim to limit excessive GWG.
Gestational weight gain (GWG) within IOM ranges was consistently associated with good maternal and fetal outcomes. Evidence at the time was judged inadequate to provide specific guidelines by grade of obesity or to support recommendations on GWG < 5 kg or gestational weight loss (GWL) for obese wome
Normal Weight
0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg
Underweight
0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg
Absolute Adjusted Risk
Small-for-gestational-age Large-for-gestational-age Emergency caesarean delivery Postpartum weightretention
0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg
Obese
0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg
0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg 0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg 0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg 0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg 0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg
Small-for-gestational-age Large-for-gestational-age Emergency caesarean delivery Postpartum weightretention Small-for-gestational-age Large-for-gestational-age Emergency Cesarean Delivery Postpartum Weight Retention Overweight
0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg 0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg 0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg 0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg 0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg
Extremely Obese
0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg 0%
10%
20%
30%
40%
50%
60%
70%
< 5 kg 5-9 kg 10-15 kg 16-19 kg 20-24 kg 25 kg
Gestational Weight Gain
Absolute Adjusted RiskAbsolute Adjusted Risk
Gestational Weight Gain
Gestational Weight Gain Gestational Weight Gain
Gestational Weight Gain
≥
≥ ≥
≥
≥
Figure 1. Gestational weight gain (GWG)-specific absolute risks for fetal and maternal outcome based on pre-pregnancy body mass index (BMI) (Weight gain during pregnancy:
reexamining the guidelines. Washington, DC: National Academies Press; 2009, Appendix G, Reprinted with permission from publisher) (10).
Observational studies have continued to provide ambiguous results on the subject.
Several large population-based cohort studies published after the release of the IOM guidelines considered it safe to set more restrictive weight gain limitations for obese women (11-14). A systematic review published in 2010 states that overweight and obese women who gain less weight than the ranges recommended by the IOM do not have an increased risk of having a low birth weight infant (15). Other researchers have argued that even the present IOM recommendations may be too restrictive for severely obese women and may be associated with increased rates of preterm births, small-for-gestational-age (SGA) infants and perinatal mortality (7). Future studies may provide sufficient evidence to lead to customized recommendations on GWG in relation not only to grade of pre-pregnancy obesity but also to individual maternal metabolic status and genetic disposition for obesity.
An increasing awareness among obstetricians about the high prevalence of exces-
sive GWG among Swedish women and the growing base of evidence regarding asso-
ciations with negative short-term and long-term maternal and fetal outcome prompted
this thesis which encompasses research in the field of antenatal lifestyle intervention
with the aim to limit excessive GWG.
BACKGROUND
Composition and timing of weight gain during pregnancy
A certain amount of weight gain is expected during pregnancy and considered essen-tial to provide the nutritional support for fetal growth and also to prepare for lactation. The placenta, growing uterus and fetus, amniotic fluid, expansion of maternal blood volume, breast tissue as well as maternal adipose tissue and extracellular fluid all contribute to total maternal GWG (Figure 2) (16).
2 4 6 8 10 12
Fetus Placenta Amniotic fluid Extracellular fluid Other tissue (fat/lean) Uterus and Breast Blood
40 w 36 w
28 w 20 w
8 w
Kg
Figure 2. Composites of gestational weight gain (GWG) (kg).
Excess weight that is not attributed to products of conception contributes to an in- crease in maternal energy stores (17). Knowledge about the degree to which pregnant women store excess energy in adipose tissue, and the sites where they do so, is still limited but excess GWG has primarily been associated with maternal fat mass accrual and not with lean mass accrual (18). Studies have so far focused mainly on women with pre-pregnancy overweight and obesity, but metabolic rate as well as the disposition to accumulate fat mass may however not be similar among normal or underweight women.
The maternal gain in adipose tissue can be deposited into visceral (central) or sub- cutaneous (peripheral) adipose tissue depots. Factors influencing site of fat deposi- tion are likely to be similar with non-pregnant women but evidence here is also still lacking. Site of fat accrual is considered of importance because fat in visceral depots and around central organs such as the liver is associated with insulin resistance, risk
of cardiovascular disease, and the metabolic syndrome (19). Further understanding of the composition of excess weight gained during pregnancy is important since the po- tential metabolic impact and contribution to long-term risk is likely to vary depending on amount of fat mass accrued as well as the site of the fat depot (19).
During the first trimester of pregnancy approximately 0.5-2 kg weight gain is ex- pected (20). The initial gain is mainly due to early placental development and ex- pansion of maternal blood volume. Fetal weight does not contribute significantly to weight gain in the first trimester. The potential difference in fetal and maternal out- come depending on the timing of excessive weight gain is still unclear. Early exces- sive weight gain has been associated with impaired maternal glucose tolerance later in pregnancy (21, 22) and greater infant adiposity at birth (22, 23) independent of total maternal GWG. Early excessive weight gain has also been suggested to be pre- dictive of total GWG. The predictive value differs however, depending on pre-preg- nancy BMI, according to a recent study (22). In that study, women with a normal pre-pregnancy BMI had a 70% probability of excess total GWG if they gained excess weight already in first trimester, while overweight and obese women had a 90% prob- ability of excess total GWG (22) if they gained excessively early in pregnancy. Fur- ther knowledge on the relevance of early GWG has implications for pre-conception counselling since very few women are admitted to maternal health care and advised on GWG in the first trimester of pregnancy.
Gestational weight gain from a Swedish perspective
The IOM guidelines have not been systematically implemented in Swedish maternal health care. Regional differences in addressing issues of maternal weight gain are re- ported and a variety of efforts are being made to help women achieve healthy weight goals before, during and after their pregnancies.
According to data from the Swedish Pregnancy Register, excessive GWG is main-
ly prevalent among women with pre-pregnancy overweight (BMI 25-29) or obesity
Grade I (BMI 30-35) . In 2013, mean GWG among women with pre-pregnancy BMI
25-29 was above IOM recommendations in all (21 out of 21) Swedish health care
regions. In all but one region, mean GWG among obese (BMI >30) women was
above IOM recommendations. Despite various efforts to limit excessive GWG there
has been a tendency during 2013-2015 towards increasing GWG in all BMI groups
except underweight women (24).
BACKGROUND
Composition and timing of weight gain during pregnancy
A certain amount of weight gain is expected during pregnancy and considered essen-tial to provide the nutritional support for fetal growth and also to prepare for lactation. The placenta, growing uterus and fetus, amniotic fluid, expansion of maternal blood volume, breast tissue as well as maternal adipose tissue and extracellular fluid all contribute to total maternal GWG (Figure 2) (16).
2 4 6 8 10 12
Fetus Placenta Amniotic fluid Extracellular fluid Other tissue (fat/lean) Uterus and Breast Blood
40 w 36 w
28 w 20 w
8 w
Kg
Figure 2. Composites of gestational weight gain (GWG) (kg).
Excess weight that is not attributed to products of conception contributes to an in- crease in maternal energy stores (17). Knowledge about the degree to which pregnant women store excess energy in adipose tissue, and the sites where they do so, is still limited but excess GWG has primarily been associated with maternal fat mass accrual and not with lean mass accrual (18). Studies have so far focused mainly on women with pre-pregnancy overweight and obesity, but metabolic rate as well as the disposition to accumulate fat mass may however not be similar among normal or underweight women.
The maternal gain in adipose tissue can be deposited into visceral (central) or sub- cutaneous (peripheral) adipose tissue depots. Factors influencing site of fat deposi- tion are likely to be similar with non-pregnant women but evidence here is also still lacking. Site of fat accrual is considered of importance because fat in visceral depots and around central organs such as the liver is associated with insulin resistance, risk
of cardiovascular disease, and the metabolic syndrome (19). Further understanding of the composition of excess weight gained during pregnancy is important since the po- tential metabolic impact and contribution to long-term risk is likely to vary depending on amount of fat mass accrued as well as the site of the fat depot (19).
During the first trimester of pregnancy approximately 0.5-2 kg weight gain is ex- pected (20). The initial gain is mainly due to early placental development and ex- pansion of maternal blood volume. Fetal weight does not contribute significantly to weight gain in the first trimester. The potential difference in fetal and maternal out- come depending on the timing of excessive weight gain is still unclear. Early exces- sive weight gain has been associated with impaired maternal glucose tolerance later in pregnancy (21, 22) and greater infant adiposity at birth (22, 23) independent of total maternal GWG. Early excessive weight gain has also been suggested to be pre- dictive of total GWG. The predictive value differs however, depending on pre-preg- nancy BMI, according to a recent study (22). In that study, women with a normal pre-pregnancy BMI had a 70% probability of excess total GWG if they gained excess weight already in first trimester, while overweight and obese women had a 90% prob- ability of excess total GWG (22) if they gained excessively early in pregnancy. Fur- ther knowledge on the relevance of early GWG has implications for pre-conception counselling since very few women are admitted to maternal health care and advised on GWG in the first trimester of pregnancy.
Gestational weight gain from a Swedish perspective
The IOM guidelines have not been systematically implemented in Swedish maternal health care. Regional differences in addressing issues of maternal weight gain are re- ported and a variety of efforts are being made to help women achieve healthy weight goals before, during and after their pregnancies.
According to data from the Swedish Pregnancy Register, excessive GWG is main-
ly prevalent among women with pre-pregnancy overweight (BMI 25-29) or obesity
Grade I (BMI 30-35) . In 2013, mean GWG among women with pre-pregnancy BMI
25-29 was above IOM recommendations in all (21 out of 21) Swedish health care
regions. In all but one region, mean GWG among obese (BMI >30) women was
above IOM recommendations. Despite various efforts to limit excessive GWG there
has been a tendency during 2013-2015 towards increasing GWG in all BMI groups
except underweight women (24).
0 3 6 9 12 15
Obesity g
rade III Obesity g
rade II Obesity g
rade I Ov
erw eight Normal
w eight Underw
eight
12.7 13.4
12.8*
10.9*
8.8
7.1
M ean GWG (kg)
Figure 3. Mean gestational weight gain (GWG) (kg) by pre-pregnancy body mass index (BMI) category, in 21 Swedish health care regions (Swedish Pregnancy Register 2014) (24).
*Mean GWG above IOM recommendations.
Among pregnant women with Grade II-III obesity (BMI >35) the majority of health care regions reported a mean GWG within recommended ranges (5-9 kg). Inadequate GWG was reported among underweight women in 9 out of 21 regions, setting focus on different issues needing to be addressed when discussing implementation of life- style intervention regarding GWG among underweight women.
Johansson et al recently published z-score charts of GWG for gestational age and maternal BMI using data from pregnancies in a geographically defined area in south- ern Sweden (Stockholm and Gotland) (25).
Figure 4. Smoothed percentiles and standard deviations (SDs), of gestational weight gain (GWG) among 141,767 women who gave birth in the Stockholm and Gotland regions of Sweden in 2008–2014. Reported by pre-pregnancy BMI group and with Institute of Medicine (IOM) recommendations on range of GWG in shaded areas (25). (Reprinted with permission from publisher
0 3 6 9 12 15
Obesity g
rade III Obesity g
rade II Obesity g
rade I Ov
erw eight Normal
w eight Underw
eight
12.7 13.4
12.8*
10.9*
8.8
7.1
M ean GWG (kg)
Figure 3. Mean gestational weight gain (GWG) (kg) by pre-pregnancy body mass index (BMI) category, in 21 Swedish health care regions (Swedish Pregnancy Register 2014) (24).
*Mean GWG above IOM recommendations.
Among pregnant women with Grade II-III obesity (BMI >35) the majority of health care regions reported a mean GWG within recommended ranges (5-9 kg). Inadequate GWG was reported among underweight women in 9 out of 21 regions, setting focus on different issues needing to be addressed when discussing implementation of life- style intervention regarding GWG among underweight women.
Johansson et al recently published z-score charts of GWG for gestational age and maternal BMI using data from pregnancies in a geographically defined area in south- ern Sweden (Stockholm and Gotland) (25).
Figure 4. Smoothed percentiles and standard deviations (SDs), of gestational weight gain (GWG) among 141,767 women who gave birth in the Stockholm and Gotland regions of Sweden in 2008–2014. Reported by pre-pregnancy BMI group and with Institute of Medicine (IOM) recommendations on range of GWG in shaded areas (25). (Reprinted with permission from publisher
Median weight gains in this Swedish population were higher than IOM recommenda- tions for many BMI categories (from overweight to obesity Grade II). Median GWG among women with obesity Grade III (BMI >40) was however, within the IOM rec- ommendations, but 10% of women in this group gained essentially no weight (0.5 kg) during pregnancy (Figure 4). Among women with normal BMI, the median GWG was within the IOM recommendations, whereas in underweight women, the median was at the lower limit. The observed distributions of GWG in this Swedish population were considerably broader than the range of the IOM recommendations.
The proportion of Swedish women with overweight or obesity (BMI>25) at ad- mission to maternal health care has increased from 25.4% in 1992 to 38.1% in 2014.
The study area for the VIGA trial, discussed in this thesis, had similar distribution of prepregnancy BMI at admission to maternal health care during the study period (Figure 5).
10%
20%
30%
40%
50%
>35,1 30-35
25-29,9 20-24,9
<20
BMI 9%
48%
26%
8%
5%
Figure 5. Distribution of maternal pre-pregnancy body mass index (BMI) in the study area at the start of recruitment to the VIGA trial in 2008.
Long-term maternal effects
Excessive GWG can affect the woman’s subsequent weight-related health. There are a number of observational studies linking excessive GWG to excessive PPWR (26) and increased risk of subsequent obesity (27). An extensive meta-analysis by Neh- ring et al concluded that excess weight gained in pregnancy was still retained >15 years postpartum (28). The degree of weight retention is, however, highly variable and women with pre-pregnancy overweight or obesity are considered more likely to experience a high degree of PPWR (15, 29).
Entering a potential subsequent pregnancy with a pre-pregnancy BMI >30 has im- plications for a number of maternal and fetal obstetric outcomes (30). Complications during pregnancy, delivery and postpartum, associated with maternal obesity will not be covered in this thesis other than to be mentioned here as a consequence of previous excessive GWG. The long-term impact of PPWR on subsequent pregnancies is, how- ever, an important factor motivating intervention to reach GWG within recommended range among women entering first pregnancy with normal BMI.
Excessiv GWG during first pregnancy
Second
pregnancy Long
term
PPWR
Fat mass
Visceral fat
LGA
CS
GDM
Prepregnancy BMI
Excessiv GWG
Fat mass
Visceral fat
GDM
PE/HT
Hyper- cholesterolemia
LGA
CS
PPWR
IUFD
Prepregancy BMI
Fat mass
Visceral fat
Type 2 DM
CVD
Metabolic syndrome
Figure 6. Consequences of excessive gestational weight gain (GWG) in women of reproduc- tive age over the course of multiple pregnancies.
Weight gain triggered by consecutive pregnancies contributes to the increased preva-
lence of overweight and obesity in reproductive age and postmenopausal women (27,
31, 32), and metabolic and/or behavioural changes that occur during the pregnancy
Median weight gains in this Swedish population were higher than IOM recommenda- tions for many BMI categories (from overweight to obesity Grade II). Median GWG among women with obesity Grade III (BMI >40) was however, within the IOM rec- ommendations, but 10% of women in this group gained essentially no weight (0.5 kg) during pregnancy (Figure 4). Among women with normal BMI, the median GWG was within the IOM recommendations, whereas in underweight women, the median was at the lower limit. The observed distributions of GWG in this Swedish population were considerably broader than the range of the IOM recommendations.
The proportion of Swedish women with overweight or obesity (BMI>25) at ad- mission to maternal health care has increased from 25.4% in 1992 to 38.1% in 2014.
The study area for the VIGA trial, discussed in this thesis, had similar distribution of prepregnancy BMI at admission to maternal health care during the study period (Figure 5).
10%
20%
30%
40%
50%
>35,1 30-35
25-29,9 20-24,9
<20
BMI 9%
48%
26%
8%
5%
Figure 5. Distribution of maternal pre-pregnancy body mass index (BMI) in the study area at the start of recruitment to the VIGA trial in 2008.
Long-term maternal effects
Excessive GWG can affect the woman’s subsequent weight-related health. There are a number of observational studies linking excessive GWG to excessive PPWR (26) and increased risk of subsequent obesity (27). An extensive meta-analysis by Neh- ring et al concluded that excess weight gained in pregnancy was still retained >15 years postpartum (28). The degree of weight retention is, however, highly variable and women with pre-pregnancy overweight or obesity are considered more likely to experience a high degree of PPWR (15, 29).
Entering a potential subsequent pregnancy with a pre-pregnancy BMI >30 has im- plications for a number of maternal and fetal obstetric outcomes (30). Complications during pregnancy, delivery and postpartum, associated with maternal obesity will not be covered in this thesis other than to be mentioned here as a consequence of previous excessive GWG. The long-term impact of PPWR on subsequent pregnancies is, how- ever, an important factor motivating intervention to reach GWG within recommended range among women entering first pregnancy with normal BMI.
Excessiv GWG during first pregnancy
Second
pregnancy Long
term
PPWR
Fat mass
Visceral fat
LGA
CS
GDM
Prepregnancy BMI
Excessiv GWG
Fat mass
Visceral fat
GDM
PE/HT
Hyper- cholesterolemia
LGA
CS
PPWR
IUFD
Prepregancy BMI
Fat mass
Visceral fat
Type 2 DM
CVD
Metabolic syndrome
Figure 6. Consequences of excessive gestational weight gain (GWG) in women of reproduc- tive age over the course of multiple pregnancies.
