Interpregnancy weight change and neonatal and infant outcomes: A systematic review and meta-analysis

PURPOSE

To synthesize evidence regarding the association between interpregnancy weight change (IPWC) in consecutive pregnancies and neonatal or infant outcomes in the subsequent pregnancy.

METHODS

Search strategy was implemented in MEDLINE, EMBASE, Web of Science, Scopus and Cochrane Library from their inception to 13 November 2023. The most adjusted odds ratio (OR) or risk ratio estimates provided by original studies were used to calculate pooled risk ratios and their corresponding 95 % confidence intervals (CI) with the DerSimonian and Laird random effects method. Publication bias was assessed by funnel plots and Egger's method, and risk of bias was assessed with The NewcastleOttawa Quality Assessment Scale.

RESULTS

Thirty-seven observational studies were included. Interpregnancy weight loss or gain were associated with large for gestational age (OR: 0.89; 95 % CI: 0.84-0.94; I2 = 83.6 % and OR: 1.33; 95 % CI:1.26-1.40; I2 = 98.9 %), and stillbirth risk (OR: 1.10; 95 % CI: 1.01-1.18; I2 = 0.0 % and OR: 1.21; 95 % CI: 1.09-1.33; I2 = 60.2 %,).

CONCLUSIONS

Findings highlight the importance of managing weight between interpregnancy periods, although these findings should be interpreted cautiously because of the possible influence of social determinants of health and other factors.

Interpregnancy Body Mass Index Change and Offspring Mortality Risk following the Second Pregnancy

OBJECTIVE

The aim of the study is to examine the impact of maternal interpregnancy body mass index (BMI) change on subsequent offspring mortality risk.

STUDY DESIGN

This is a retrospective cohort study of women who had two consecutive live singleton deliveries of at least 20 weeks' gestation from the Utah Population Database. Our exposure was defined as interpregnancy BMI change from the date of first delivery to the conception date of subsequent pregnancy. We categorized BMI change as: < - 1, -1 to 0, 0 to <1 (reference), 1 to 2, 2 to 4, ≥4 kg/m2. Our primary outcome was all-cause age-specific mortality during four time periods: neonatal (≤28 days), infant (29 days to <1 year old), childhood ((≥1 to <5 years old), and late childhood (5 to <18 years old). We also examined mortality specifically attributed to congenital anomalies. Analyses used Cox proportional hazard models stratified by full term (≥37 weeks) and preterm (<37 weeks) deliveries. All models were adjusted for relevant confounders.

RESULTS

Of 266,752 women, among full-term deliveries, women with a BMI increase of 4 kg/m2 or more had an increased risk of neonatal mortality in their subsequent pregnancy (hazard ratio or HR = 1.72, 95% confidence interval or CI: 1.23-2.41) Women who lost 1 kg/m2 or more between deliveries also had increased neonatal mortality (HR = 1.46, 95% CI: 1.04-2.05). There were no differences in infant, early, or late childhood mortality by interpregnancy BMI change. Maternal interpregnancy interval weight loss of 1 kg/m2 or more and weight gain of ≥4 kg/m2 also had increased risk of mortality associated with congenital anomalies or conditions arising during the neonatal period following their subsequent delivery.

CONCLUSION

Women with significant interpregnancy weight gain and modest weight loss have a significant increased risk of neonatal mortality following their subsequent pregnancy.

KEY POINTS

· Significant weight gain between deliveries increases the risk of neonatal death.. · Modest weight loss between deliveries increases the risk of neonatal death.. · This risk may be partially explained by increased risk of congenital malformations..

Maternal overweight and obesity during pregnancy: strategies to improve outcomes for women, babies, and children

INTRODUCTION

Women with overweight and obesity, and their children, are at increased risk of adverse pregnancy, birth, and longer term health outcomes, believed to be compounded by excessive gestational weight gain (GWG). Research to date has focused on interventions to reduce excessive GWG through changes to maternal diet and/or lifestyle.

AREAS COVERED

Current clinical recommendations for GWG vary according to a woman's early pregnancy body mass index, based on assumptions that associations between GWG and adverse pregnancy outcomes are causal in nature, and modifiable. While there are small differences in GWG following pregnancy interventions, there is little evidence for clinically relevant effects on pregnancy, birth, and longer term childhood outcomes. This review considers interventional studies targeting women with overweight or obesity to reduce GWG in an effort to improve maternal and infant health, and the current evidence for interventions prior to conception.

EXPERT OPINION

GWG is not modifiable via diet and lifestyle change, and continued efforts to find the 'right' intervention for women with overweight and obesity during pregnancy are unjustified. Researchers should focus on gathering evidence for interventions prior to pregnancy to optimize maternal health and weight to improve pregnancy, birth, and longer term health outcomes associated with obesity.

Interpregnancy weight change: associations with severe maternal morbidity and neonatal outcomes

BACKGROUND

Prepregnancy body mass index and gestational weight gain have been linked with severe maternal morbidity, suggesting that weight change between pregnancies may also play a role, as it does for neonatal outcomes.

OBJECTIVE

This study assessed the association of changes in prepregnancy body mass index between 2 consecutive singleton pregnancies with the outcomes of severe maternal morbidity, stillbirth, and small- and large-for-gestational-age infants in the subsequent pregnancy.

STUDY DESIGN

This observational study was based on birth records from 1,111,032 consecutive pregnancies linked to hospital discharge records in California (2007-2017). Interpregnancy body mass index change between the beginning of an index pregnancy and the beginning of the subsequent pregnancy was calculated from self-reported weight and height. Severe maternal morbidity was defined based on the Centers for Disease Control and Prevention index, including and excluding transfusion-only cases. We used multivariable log-binomial regression models to estimate adjusted risks, overall and stratified by prepregnancy body mass index at index birth.

RESULTS

Substantial interpregnancy body mass index gain (≥4 kg/m2) was associated with severe maternal morbidity in crude but not adjusted analyses. Substantial interpregnancy body mass index loss (>2 kg/m2) was associated with increased risk of severe maternal morbidity (adjusted relative risk, 1.13; 95% confidence interval (1.07-1.19), and both substantial loss (adjusted relative risk, 1.11 [1.02-1.19]) and gain (≥4 kg/m2; adjusted relative risk, 1.09 [1.02-1.17]) were associated with nontransfusion severe maternal morbidity. Substantial loss (adjusted relative risk, 1.17 [1.05-1.31]) and gain (1.26 [1.14-1.40]) were associated with stillbirth. Body mass index gain was positively associated with large-for-gestational-age infants and inversely associated with small-for-gestational-age infants.

CONCLUSION

Substantial interpregnancy body mass index changes were associated with modestly increased risk of severe maternal morbidity, stillbirth, and small- and large-for-gestational-age infants.

Does prepregnancy weight change have an effect on subsequent pregnancy health outcomes? A systematic review and meta-analysis

International guidelines recommend women with an overweight or obese body mass index (BMI) aim to reduce their body weight prior to conception to minimize the risk of adverse perinatal outcomes. Recent systematic reviews have demonstrated that interpregnancy weight gain increases women's risk of developing adverse pregnancy outcomes in their subsequent pregnancy. Interpregnancy weight change studies exclude nulliparous women. This systematic review and meta-analysis was conducted following MOOSE guidelines and summarizes the evidence of the impact of preconception and interpregnancy weight change on perinatal outcomes for women regardless of parity. Sixty one studies met the inclusion criteria for this review and reported 34 different outcomes. We identified a significantly increased risk of gestational diabetes (OR 1.88, 95% CI 1.66, 2.14, I²  = 87.8%), hypertensive disorders (OR 1.46 95% CI 1.12, 1.91, I²  = 94.9%), preeclampsia (OR 1.92 95% CI 1.55, 2.37, I²  = 93.6%), and large-for-gestational-age (OR 1.36, 95% CI 1.25, 1.49, I²  = 92.2%) with preconception and interpregnancy weight gain. Interpregnancy weight loss only was significantly associated with increased risk for small-for-gestational-age (OR 1.29 95% CI 1.11, 1.50, I²  = 89.9%) and preterm birth (OR 1.06 95% CI 1.00, 1.13, I²  = 22.4%). Our findings illustrate the need for effective preconception and interpregnancy weight management support to improve pregnancy outcomes in subsequent pregnancies.

Does interpregnancy BMI change affect the risk of complications in the second pregnancy? Analysis of pooled data from Aberdeen, Finland and Malta

Objective

Weight management interventions during pregnancy have had limited success in reducing the risk of pregnancy complications. Focus has now shifted to pre-pregnancy counselling to optimise body weight before subsequent conception. We aimed to assess the effect of interpregnancy body mass index (BMI) change on the risk of perinatal complications in the second pregnancy.

Methods

A cohort study was performed using pooled maternity data from Aberdeen, Finland and Malta. Women with a BMI change of ±2 kg/m² between their first and second pregnancies were compared with those who were BMI stable (remained within ±2 kg/m²). Outcomes assessed included pre-eclampsia (PE), intrauterine growth restriction (IUGR), preterm birth, birth weight, and stillbirth in the second pregnancy. We also assessed the effect of unit change in BMI for PE and IUGR. Logistic regression was used to calculate odds ratios with 95% confidence intervals.

Results

An increase of ≥2 kg/m² between the first two pregnancies increased the risk of PE (1.66 (1.49–1.86)) and high birthweight (>4000 g) (1.06 (1.03–1.10)). A reduction of ≥2 kg/m² increased the chance of IUGR (1.15 (1.01–1.31)) and preterm birth (1.14 (1.01–1.30)), while reducing the risk of instrumental delivery (0.75 (0.68–0.85)) and high birthweight (0.93 (0.87–0.98)). Reducing BMI did not significantly decrease PE risk in women with obesity or those with previous PE. A history of PE or IUGR in the first pregnancy was the strongest predictor of recurrence independent of interpregnancy BMI change (5.75 (5.30–6.24) and (7.44 (6.71–8.25), respectively).

Conclusion

Changes in interpregnancy BMI have a modest impact on the risk of high birthweight, PE and IUGR in contrasting directions. However, a prior history of PE and IUGR is the dominant predictor of recurrence at second pregnancy.

Short-term weight change and live birth among women with unexplained infertility and polycystic ovary syndrome undergoing ovulation induction

OBJECTIVE

To determine if short-term weight change among women with unexplained infertility (UI) and polycystic ovary syndrome (PCOS) undergoing ovulation induction is associated with live birth.

DESIGN

Secondary analysis of randomized trials.

SETTING

Multicenter fertility trial sites.

PATIENT(S)

A total of 900 women with UI and 750 women with PCOS.

MAIN OUTCOME MEASURE(S)

Live birth.

INTERVENTION(S)

Weight assessment at enrollment and start of up to 4-5 cycles of clomiphene, letrozole, or gonadotropins and intrauterine insemination for women with UI and clomiphene or letrozole with regular intercourse for women with PCOS.

RESULT(S)

Weight data were available for 856 women with UI and 697 women with PCOS. Mean weight change was -0.2 ± 0.3 kg among women with UI and +2.2 ± 0.2 kg among women with PCOS and did not differ based on treatment allocation. There were 115 women with PCOS (16.4%) who gained ≥3 kg. Increased body mass index and three or more cycles were associated with weight gain in women with PCOS. There was no difference in live birth rate among women with PCOS and ≥3 kg weight gain and women with PCOS who did not gain weight.

CONCLUSION(S)

Women with PCOS gained an average of 2.2 kg regardless of the medication received, whereas women with UI experienced no short-term weight change during ovulation induction. Weight gain in women with PCOS was not associated with live birth rate.

Association of Overweight and Obesity Development Between Pregnancies With Stillbirth and Infant Mortality in a Cohort of Multiparous Women

OBJECTIVE

To identify the association of newly developed prepregnancy overweight and obesity with stillbirth and infant mortality.

METHODS

We studied subsequent pregnancies of mothers who were normal weight at fertilization of their first identified pregnancy, from a population-based cohort that linked birth registry with death records in Pennsylvania, 2003-2013. Women with newly developed prepregnancy overweight and obesity were defined as those whose body mass index (BMI) before second pregnancy was between 25 and 29.9 or 30 or higher, respectively. Our main outcomes of interest were stillbirth (intrauterine death at 20 weeks of gestation or greater), infant mortality (less than 365 days after birth), neonatal death (less than 28 days after birth) and postneonatal death (29-365 days after birth). Associations of both prepregnancy BMI categories and continuous BMI with each outcome were estimated by nonparametric targeted minimum loss-based estimation and inverse-probability weighted dose-response curves, respectively, adjusting for race-ethnicity, smoking, and other confounders (eg, age, education).

RESULTS

A cohort of 212,889 women were included for infant mortality analysis (192,941 women for stillbirth analysis). The crude rate of stillbirth and infant mortality in these final analytic cohorts were 3.3 per 1,000 pregnancies and 2.9 per 1,000 live births, respectively. Compared with women who stayed at a normal weight in their second pregnancies, those becoming overweight had 1.4 (95% CI 0.6-2.1) excess stillbirths per 1,000 pregnancies. Those becoming obese had 3.6 (95% CI 1.3-5.9) excess stillbirths per 1,000 pregnancies and 2.4 (95% CI 0.4-4.4) excess neonatal deaths per 1,000 live births. There was a dose-response relationship between prepregnancy BMI increases of more than 2 units and increased risk of stillbirth and infant mortality. In addition, BMI increases were associated with higher risks of infant mortality among women with shorter interpregnancy intervals (less than 18 months) compared with longer intervals.

CONCLUSION

Transitioning from normal weight to overweight or obese between pregnancies was associated with an increased risk of stillbirth and neonatal mortality.

Obstetric Care Consensus No. 8: Interpregnancy Care

Interpregnancy care aims to maximize a woman's level of wellness not just in between pregnancies and during subsequent pregnancies, but also along her life course. Because the interpregnancy period is a continuum for overall health and wellness, all women of reproductive age who have been pregnant regardless of the outcome of their pregnancies (ie, miscarriage, abortion, preterm, full-term delivery), should receive interpregnancy care as a continuum from postpartum care. The initial components of interpregnancy care should include the components of postpartum care, such as reproductive life planning, screening for depression, vaccination, managing diabetes or hypertension if needed, education about future health, assisting the patient to develop a postpartum care team, and making plans for long-term medical care. In women with chronic medical conditions, interpregnancy care provides an opportunity to optimize health before a subsequent pregnancy. For women who will not have any future pregnancies, the period after pregnancy also affords an opportunity for secondary prevention and improvement of future health.

Invited Commentary: The Causal Association Between Obesity and Stillbirth-Strengths and Limitations of the Consecutive-Pregnancies Approach

There has been a resurgence in analyses of consecutive pregnancies (or similarly, sibling designs) in perinatal and pediatric epidemiology. These approaches have attractive qualities for estimating associations with complex multifactorial exposures like obesity. In an article appearing in this issue of the Journal, Yu et al. (Am J Epidemiol. 2019;188(7):1328-1336) apply a consecutive-pregnancies approach to characterize the risk of stillbirth among women who develop obesity between pregnancies ("incident obesity"). Working within a causal framework and using parametric and nonparametric estimation techniques, the authors find an increase in stillbirth risk associated with incident obesity. Risk differences varied between 0.4 per 1,000 births (95% confidence interval (CI): 0.1, 0.7) and 6.9 per 1,000 births (95% CI: 3.7, 10.0), and risk ratios ranged from 1.12 (95% CI: 1.02, 1.23) to 2.99 (95% CI: 2.19, 4.08). The strengths of this approach include starting from a clearly defined causal estimand and exploring the sensitivity of parameter estimates to model selection. In this commentary, we put these findings in the broader context of research on obesity and birth outcomes and highlight concerns regarding the generalizability of results derived from within-family designs. We conclude that while causal inference is an important goal, in some instances focusing on formulation of a causal question drives results away from broad applicability.

Interpregnancy Care

Interpregnancy care aims to maximize a woman's level of wellness not just in between pregnancies and during subsequent pregnancies, but also along her life course. Because the interpregnancy period is a continuum for overall health and wellness, all women of reproductive age who have been pregnant regardless of the outcome of their pregnancies (ie, miscarriage, abortion, preterm, full-term delivery), should receive interpregnancy care as a continuum from postpartum care. The initial components of interpregnancy care should include the components of postpartum care, such as reproductive life planning, screening for depression, vaccination, managing diabetes or hypertension if needed, education about future health, assisting the patient to develop a postpartum care team, and making plans for long-term medical care. In women with chronic medical conditions, interpregnancy care provides an opportunity to optimize health before a subsequent pregnancy. For women who will not have any future pregnancies, the period after pregnancy also affords an opportunity for secondary prevention and improvement of future health.

Recent advances in understanding the relationship between long- and short-term weight change and fertility

The impact of excess body weight on fertility is well recognized among both women attempting to conceive spontaneously and those attempting to conceive with medical assistance. Although many leading societies of reproductive medicine have proposed weight loss as a means to counteract the negative consequences of obesity on fertility, there is limited research on this topic. In this review, we provide a brief overview of the recent advances in the literature focused on how long- and short-term weight change affects fertility among women. Overall, despite initial hope that weight loss may be beneficial for fertility, two large well-conducted randomized controlled trials have consistently shown that short-term weight loss among overweight and obese women undergoing infertility treatment does not improve a woman's probability of live birth. The observational evidence among women attempting to conceive without medical assistance also suggests limited benefits of weight loss on fecundity or pregnancy loss. In contrast, substantial weight gain between consecutive pregnancies, in the year prior to pregnancy attempt, and throughout adulthood appears to be harmful for not only time to pregnancy but also pregnancy maintenance. Future research focused on efforts to prevent weight gain during adulthood is needed to better understand whether these types of interventions may have beneficial effects on fertility.

Weight change across the start of three consecutive pregnancies and the risk of maternal morbidity and SGA birth at the second and third pregnancy

BACKGROUND

Weight-change across parities and/or current BMI may influence maternal and fetal morbidity and requires to be differentiated to better inform weight-management guidance.

METHODS

Direction, pattern and magnitude of weight-change across three consecutive parities and thereby two inter-pregnancy periods was described in 5079 women. The association between inter-pregnancy weight-change versus current BMI and adverse maternal events, SGA-birth and preterm delivery at second and third pregnancy were investigated by logistic regression.

RESULTS

More women gained weight across the defined childbearing period than lost it, with ~35% of normal and overweight women gaining sufficient weight to move up a BMI-category. Nine patterns of weight-change were defined across two inter-pregnancy periods and 50% of women remained weight-stable throughout (within 2BMI units/period). Women who were overweight/obese at first pregnancy had higher risk of substantial weight-gain and loss (>10kg) during each of two inter-pregnancy periods. Inter-pregnancy weight-gain (> 2BMI units) between first and second pregnancy increased the risk of maternal morbidity (1or more event of hypertensive disease, caesarean-section, thromboembolism) at second pregnancy, while weight-loss (>2BMI units) increased the risk of SGA-birth. Similarly, increased risk of maternal morbidity at the third pregnancy was influenced by weight-gain during both inter-pregnancy periods but not by current BMI-category. Both weight-gain between first and second pregnancy, and being overweight/obese by third pregnancy protected the fetus against SGA-birth whereas weight-loss between second and third pregnancy doubled the SGA risk.

CONCLUSION

Half the women studied exhibited significant weight-fluctuations. This influenced their risk of maternal morbidity and SGA-birth at second and third pregnancy.

Pre-pregnancy body mass index and inter-pregnancy weight change among women of Russian, Somali and Kurdish origin and the general Finnish population

Objectives: We studied the differences in the mean pre-pregnancy body mass index (BMI) and mean inter-pregnancy weight change in women of Russian, Somali and Kurdish origin and women in the general Finnish population. Methods: The population-based samples were from the Migrant Health and Wellbeing Study and the Health 2011 Survey conducted in six cities in Finland in 2010–2012. This study included women with at least one birth in Finland. Data on their previous pregnancies in Finland were obtained from the National Medical Birth Register for 318 Russian, 584 Somali and 373 Kurdish origin women and for 243 women in the general Finnish population (reference group). Data on pre-pregnancy weight and height were self-reported in early pregnancy. Linear logistic regression was the main method of analysis. Results: The unadjusted mean pre-pregnancy BMI was higher in Somali (27.0 kg/m2, p<0.001) and Kurdish (25.8 kg/m2, p<0.001) women, but lower in Russian (22.2 kg/m2, p<0.001) women than in the reference group (24.1 kg/m2). The adjusted coefficients for the difference in the mean pre-pregnancy BMI were −1.93 (95% CI −2.77 to −1.09) for Russian, 1.82 (95% CI 0.89–2.75) for Somali and 1.30 (95% CI 0.43–2.17) for Kurdish women compared with the reference group. Among women with at least two births, no statistically significant difference was observed in the mean inter-pregnancy weight change between the migrant groups and the reference group. Conclusions: Somali and Kurdish women had higher mean pre-pregnancy BMIs than women in the general Finnish population and may need special support and health promotion strategies for weight management.

Preconceptional and maternal obesity: epidemiology and health consequences

Obesity in women of reproductive age is increasing in prevelance worldwide. Obesity reduces fertility and increases time taken to conceive, and obesity-related comorbidities (such as type 2 diabetes and chronic hypertension) heighten the risk of adverse outcomes for mother and child if the woman becomes pregnant. Pregnant women who are obese are more likely to have early pregnancy loss, and have increased risk of congenital fetal malformations, delivery of large for gestational age infants, shoulder dystocia, spontaneous and medically indicated premature birth, and stillbirth. Late pregnancy complications include gestational diabetes and pre-eclampsia, both of which are associated with long-term morbidities post partum. Women with obesity can also experience difficulties during labour and delivery, and are more at risk of post-partum haemorrhage. Long-term health risks are associated with weight retention after delivery, and inherent complications for the next pregnancy. The wellbeing of the next generation is also compromised. All these health issues could be avoided by prevention of obesity among women of reproductive age, which should be viewed as a global public health priority. For women who are already obese, renewed efforts should be made towards improved management during pregnancy, especially of blood glucose, and increased attention to post-partum weight management. Effective interventions, tailored to ethnicity and culture, are needed at each of these stages to improve the health of women and their children in the context of the global obesity epidemic.

Inter-Pregnancy Weight Change and the Risk of Recurrent Pregnancy Complications

Women with specific adverse pregnancy outcomes in their first pregnancy may be receptive to inter-pregnancy weight management guidance aimed at preventing these complications reoccurring in subsequent pregnancies. Thus the association between inter-pregnancy weight change and the risk of recurrent pregnancy complications at the second pregnancy was investigated in a retrospective cohort study of 24,520 women with their first-ever and second consecutive deliveries in Aberdeen using logistic regression. Compared with women who were weight stable, weight loss (>2BMI units) between pregnancies was associated with an increased risk of recurrent small for gestational age (SGA) birth and elective Cesarean-section, and was protective against recurrent pre-eclampsia, placental oversize and large for gestational age (LGA) birth. Conversely weight gain (>2BMI units) between pregnancies increased the risk of recurrent gestational hypertension, placental oversize and LGA birth and was protective against recurrent low placental weight and SGA birth. The relationships between weight gain, and placental and birth weight extremes were evident only in women with a healthy weight at first pregnancy (BMI<25units), while that between weight gain and the increased risk of recurrent gestational hypertension was largely independent of first pregnancy BMI. No relationship was detected between inter-pregnancy weight change and the risk of recurrent spontaneous preterm delivery, labour induction, instrumental delivery, emergency Cesarean-section or postpartum hemorrhage. Therefor inter-pregnancy weight change impacts the risk of recurrent hypertensive disorders, SGA and LGA birth and women with a prior history of these specific conditions may benefit from targeted nutritional advice to either lose or gain weight after their first pregnancy.

Weight change between successive pregnancies and risks of stillbirth and infant mortality: a nationwide cohort study

BACKGROUND

Maternal overweight and obesity are risk factors for stillbirth and infant mortality. Whether temporal changes in maternal weight affect these risks is not clear. We aimed to assess whether change of BMI between first and second pregnancies affects risks of stillbirth and infant mortality in the second-born offspring.

METHODS

In a Swedish population-based cohort of women who gave birth to their first and second child between Jan 1, 1992, and Dec 31, 2012, we investigated associations between change in maternal body-mass index (BMI) during early pregnancy from first to second pregnancies and risks of stillbirth and neonatal, postneonatal, and infant mortality after the second pregnancy. Relative risks (RRs) for each outcome according to BMI change categories were calculated with binomial regression.

FINDINGS

Complete information was available for 456,711 (77.7%) of 587,710 women who had their first and second single births in the study period. Compared with women with a stable BMI (change between -1 kg/m(2) and <1 kg/m(2)) between pregnancies, the adjusted RRs for women who gained at least 4 BMI units between pregnancies were 1.55 (95% CI 1.23-1.96) for stillbirth and 1.29 (1.00-1.67) for infant mortality. Stillbirth risks increased linearly with increased BMI gain. Risks of infant mortality in second pregnancy only increased with BMI gain in women with healthy BMI (<25 kg/m(2)) during first pregnancy; the adjusted RR for healthy weight women who gained 2 to less than 4 BMI units was 1.27 (1.01-1.59) and for those who gained 4 BMI units or more the adjusted RR was 1.60 (1.16-2.22). In overweight women (BMI ≥25 kg/m(2)), weight loss before pregnancy reduced risk of neonatal mortality.

INTERPRETATION

Our findings emphasise the need to prevent weight gain before pregnancy in healthy and overweight women and that weight loss should be promoted in overweight women.

FUNDING

Swedish Research Council for Health, Working Life and Welfare, and Karolinska Institutet.

Prepregnancy and early adulthood body mass index and adult weight change in relation to fetal loss

OBJECTIVE

To examine prospectively the relationships of prepregnancy body mass index (BMI), BMI at age 18 years, and weight change since age 18 years with risk of fetal loss.

METHODS

Our prospective cohort study included 25,719 pregnancies reported by 17,027 women in the Nurses' Health Study II between 1990 and 2009. In 1989, height, current weight, and weight at age 18 years were self-reported. Current weight was updated every 2 years thereafter. Pregnancies were self-reported, with case pregnancies lost spontaneously and comparison pregnancies ending in ectopic pregnancy, induced abortion, or live birth.

RESULTS

Incident fetal loss was reported in 4,494 (17.5%) pregnancies. Compared with those of normal BMI, the multivariate relative risks of fetal loss were 1.07 (95% CI [confidence interval] 1.00-1.15) for overweight women, 1.10 (95% CI 0.98-1.23) for class I obese women, and 1.27 (95% CI 1.11-1.45) for class II and class III obese women (P trend ≤ .001). Body mass index at age 18 years was not associated with fetal loss (P trend=.59). Compared with women who maintained a stable weight (± 4 kg) between age 18 years and before pregnancy, women who lost weight had a 20% (95% CI 9-29%) lower risk of fetal loss. This association was stronger among women who were overweight at age 18 years.

CONCLUSION

Being overweight or obese before pregnancy was associated with higher risk of fetal loss. In women overweight or obese at age 18 years, losing 4 kg or more was associated with a lower risk of fetal loss.

LEVEL OF EVIDENCE

: II.

Interpregnancy body mass index change and success of term vaginal birth after cesarean delivery

OBJECTIVE

We investigated the effect of interpregnancy body mass index (BMI) change on success of term vaginal birth after cesarean (VBAC) among normal, overweight and obese women.

STUDY DESIGN

Using 1992-2009 Washington State birth certificate data linked with hospitalization records, we conducted a population-based retrospective cohort study of nulliparous women (BMI ≥18.5 kg/m(2)) with a primary cesarean in their first birth and a term trial of labor in their second. Interpregnancy weight change (difference between first and second prepregnancy BMIs) was categorized as maintenance (<1 BMI unit change), loss (≥1 unit), moderate gain (≥1 and <2 units), high gain (≥2 units). We estimated relative risks of VBAC success using generalized linear models with a log-link function, adjusting for maternal age, race/ethnicity, nativity, marital status, education, smoking, primary cesarean indication, interpregnancy interval, birth year for second birth, and prenatal care adequacy.

RESULTS

Among 8302 women who attempted a term trial of labor, 65% had a successful VBAC. Women with normal BMI before their first pregnancy experienced an 8% decrease in VBAC success with moderate gain (relative risk [RR], 0.92; 95% confidence interval [CI], 0.87-0.98) and a 12% decrease in success with high gain (RR, 0.88; 95% CI, 0.83-0.93), compared with normal weight women who maintained weight. Weight loss increased VBAC success in women who were overweight (RR, 1.12; 95% CI, 1.01-1.25) or obese before their first delivery (RR, 1.24; 95% CI, 1.04-1.49), compared with overweight and obese women, respectively, who maintained weight.

CONCLUSION

Women can improve their chance of successful VBAC through interpregnancy weight management.

Inter-pregnancy weight change impacts placental weight and is associated with the risk of adverse pregnancy outcomes in the second pregnancy

BACKGROUND

The inter-pregnancy period is considered a teachable moment when women are receptive to weight- management guidance aimed at optimising pregnancy outcome in subsequent pregnancies. In population based studies inter-pregnancy weight change is associated with several adverse pregnancy outcomes but the impact on placental size is unknown.

METHODS

The association between inter-pregnancy weight change and the primary risk of adverse pregnancy outcomes in the second pregnancy was investigated in 12,740 women with first two consecutive deliveries at a single hospital using logistic regression.

RESULTS

Compared with women who were weight stable, weight loss (>1BMI unit) between pregnancies was associated with an increased risk of spontaneous preterm delivery, low placental weight and small for gestational age (SGA) birth, while weight gain (>3BMI units) increased the risk of pre-eclampsia, gestational hypertension, emergency caesarean section, placental oversize and large for gestational age (LGA) birth at the second pregnancy. The relationship between weight gain and pre-eclampsia risk was evident in women who were overweight at first pregnancy only (BMI ≥25 units), while that between weight loss and preterm delivery was confined to women with a healthy weight at first pregnancy (BMI <25 units). In contrast, the association between weight loss and SGA was independent of first pregnancy BMI. A higher percentage of women who were obese at first pregnancy were likely to experience a large weight gain (P < 0.01) or weight loss (P < 0.001) between consecutive pregnancies compared with the normal BMI reference group.

CONCLUSION

Inter-pregnancy weight change in either direction increases the risk of a number of contrasting pregnancy complications, including extremes of placental weight. The placenta may lie on the causal pathway between BMI change and the risk of LGA or SGA birth.

Interpregnancy weight change and risk for adverse perinatal outcome

OBJECTIVE

To examine the association between interpregnancy weight change and the risk for adverse maternal and neonatal outcomes.

METHODS

All live-born singleton births delivered at 21-42 weeks of gestation in women who had their first two consecutive births between 2009 and 2011 in Flanders (the northern part of Belgium) and who were included in the Study Center for Perinatal Epidemiology database (N=7,897) were included. Interpregnancy weight change was calculated as the difference between the prepregnancy body mass index (BMI) of the first pregnancy and the prepregnancy BMI of the second pregnancy. Multivariate logistic regression analysis to predict gestational diabetes mellitus, pregnancy-induced hypertension, cesarean delivery, macrosomia (4,000 g or greater), low birth weight (less than 2,500 g), and congenital malformations were performed.

RESULTS

The adjusted odds ratio (OR) for gestational diabetes mellitus was 2.25 (95% confidence interval [CI] 1.33-3.78; P=.002) for interpregnancy weight retention of 2 or more BMI units, and the adjusted OR for pregnancy-induced hypertension was 3.76 (95% CI 2.16-6.57; P<.001) with an increase of 3 or more BMI units between pregnancies, but these associations were only present in underweight and normal-weight women. In overweight and obese women, the adjusted OR was 2.04 (95% CI 1.41-2.95; P<.001) for cesarean delivery for an interpregnancy weight retention of 2 or more BMI units. In underweight and normal-weight women, the risk for macrosomia was halved if women lost more than 1 BMI unit between pregnancies, but at the same time, the risk for low birth weight doubled.

CONCLUSION

We show that weight retention between the first and second pregnancy is associated with an increased risk for perinatal complications, even in underweight and normal-weight women. Stabilizing interpregnancy weight appears an important target for reducing adverse perinatal outcomes in a second pregnancy.

LEVEL OF EVIDENCE

II.

Maternal adiposity--a determinant of perinatal and offspring outcomes?

Experimental and animal data suggest that maternal obesity during pregnancy adversely affects offspring health in the short-term and the long-term. Whether these effects occur in humans and influence population health is less clear. This Review explores evidence from intervention studies and observational studies that have used designs (such as family-based comparisons and Mendelian randomization) that might help improve understanding of the causal effects of maternal obesity in humans. Collectively, human studies provide evidence that maternal overweight and obesity is causally related to pregnancy complications, increased offspring weight and adiposity at birth, and the difficulties associated with delivery of large-for-gestational-age infants. The underlying mechanisms for these effects probably involve maternal and fetal dysregulation of glucose, insulin, lipid and amino acid metabolism. Some evidence exists that extreme maternal obesity (BMI ≥40 kg/m(2)) is causally related to a long-term increase in offspring adiposity, but further exploration of this relationship is needed. High gestational weight gain may result in a long-term increase in offspring adiposity if women are already overweight or have obesity at the start of pregnancy. To date, little high-quality human evidence exists that any of these effects are mediated by epigenetic mechanisms, but approaches to appropriately test this possibility are being developed.