Early-pregnancy weight gain and the risk of preeclampsia: A case-cohort study

Do current pregnancy weight gain guidelines balance risks of adverse maternal and child health in a United States cohort?

BACKGROUND

The Institute of Medicine pregnancy weight gain guidelines were developed without evidence linking high weight gain to maternal cardiometabolic disease and child obesity. The upper limit of current recommendations may be too high for the health of the pregnant individual and child.

OBJECTIVES

The aim of this study was to identify the range of pregnancy weight gain for pregnancies within a normal body mass index (BMI) range that balances the risks of high and low weight gain by simultaneously considering 10 different health conditions.

METHODS

We used data from an United States prospective cohort study of nulliparae followed until 2 to 7 y postpartum (N = 2344 participants with a normal BMI). Pregnancy weight gain z-score was the main exposure. The outcome was a composite consisting of the occurrence of ≥1 of 10 adverse health conditions that were weighted for their seriousness. We used multivariable Poisson regression to relate weight gain z-scores with the weighted composite outcome.

RESULTS

The lowest risk of the composite outcome was at a pregnancy weight gain z-score of -0.6 SD (standard deviation) (equivalent to 13.1 kg at 40 wk). The weight gain ranges associated with no more than 5%, 10%, and 20% increase in risks were -1.0 to -0.2 SD (11.2-15.3 kg), -1.4 to 0 SD (9.4-16.4 kg), and -2.0 to 0.4 SD (7.0-18.9 kg). When we used a lower threshold to define postpartum weight increase in the composite outcome (>5 kg compared with >10 kg), the ranges were 1.6 to -0.7 SD (8.9-12.6 kg), -2.2 to -0.3 SD (6.3-14.7 kg), and ≤0.2 SD (≤17.6 kg). Compared with the ranges of the current weight gain guidelines (-0.9 to -0.1 SD, 11.5-16 kg), the lower limits from our data tended to be lower while upper limits were similar or lower.

CONCLUSIONS

If replicated, our results suggest that policy makers should revisit the recommended pregnancy weight gain range for individuals within a normal BMI range.

Gestational weight gain of multiparas and risk of primary preeclampsia: a retrospective cohort study in Shanghai

BACKGROUND

In all studies conducted so far, there was no report about the correlation between excessive gestational weight gain (GWG) and the risk of preeclampsia (PE) in multiparas, especially considering that multiparity is a protective factor for both excessive GWG and PE. Thus, the aim of this retrospective cohort study was to determine whether GWG of multiparas is associated with the increased risk of PE.

METHODS

This was a study with 15,541 multiparous women who delivered in a maternity hospital in Shanghai from 2017 to 2021, stratified by early-pregnancy body mass index (BMI) category. Early-pregnancy body weight, height, week-specific and total gestational weight gain as well as records of antenatal care were extracted using electronic medical records, and antenatal weight gain measurements were standardized into gestational age-specific z scores.

RESULTS

Among these 15,541 multiparous women, 534 (3.44%) developed preeclampsia. The odds of preeclampsia increased by 26% with every 1 z score increase in pregnancy weight gain among normal weight women and by 41% among overweight or obese women. For normal weight women, pregnant women with preeclampsia gained more weight than pregnant women without preeclampsia beginning at 25 weeks of gestation, while accelerated weight gain was more obvious in overweight or obese women after 25 weeks of gestation.

CONCLUSIONS

In conclusion, excessive GWG in normal weight and overweight or obese multiparas was strongly associated with the increased risk of preeclampsia. In parallel, the appropriate management and control of weight gain, especially in the second and third trimesters, may lower the risk of developing preeclampsia.

Investigating the Shape and Strength of the Relationship Between Maternal Weight Gain and Gestational Age at Delivery in Twin and Singleton Pregnancies

Both inadequate and excessive maternal weight gain are correlated with preterm delivery in singleton pregnancies, yet this relationship has not been adequately studied in twins. We investigated the relationship between time-varying maternal weight gain and gestational age at delivery in twin pregnancies and compared it with that in singletons delivered in the same study population. We used serial weight measurements abstracted from charts for twin and singleton pregnancies delivered during 1998-2013 in Pittsburgh, Pennsylvania. Our exposure was time-varying weight gain z score, calculated using gestational age-standardized and prepregnancy body mass index-stratified twin- and singleton-specific charts, and our outcome was gestational age at delivery. Our analyses used a flexible extension of the Cox proportional hazards model that allowed for nonlinear and time-dependent effects. We found a U-shaped relationship between weight gain z score and gestational age at delivery among twin pregnancies (lowest hazard of delivery observed at z score = 1.2), which we attributed to increased hazard of early preterm spontaneous delivery among pregnancies with low weight gain and increased hazard of late preterm delivery without labor among pregnancies with high weight gain. Our findings may be useful for updating provisional guidelines for maternal weight gain in twin pregnancies.

Early Gestational Weight Gain and the Risk of Preeclampsia in Dichorionic Twin Pregnancies

OBJECTIVE

The purpose of our study was to evaluate the body mass index (BMI)-specific association between early gestational weight gain (GWG) in dichorionic twin pregnancies and the risk of preeclampsia.

STUDY DESIGN

We conducted a retrospective cohort study of all dichorionic twin pregnancies from 1998 to 2013. Data were obtained from a perinatal database and chart abstraction. Prepregnancy BMI was categorized as normal (18.5-24.9 kg/m2), overweight (25-29.9 kg/m2), and obese (≥30 kg/m2). Early GWG was defined as the last measured weight from 160/7 to 196/7weeks' gestation minus prepregnancy weight. GWG was standardized for gestational duration using BMI-specific z-score charts for dichorionic pregnancies. Preeclampsia was diagnosed using American College of Obstetricians and Gynecologists criteria and identified with International Classification of Diseases-9 coding. Early GWG z-score was modeled as a three-level categorical variable (≤ - 1 standard deviation [SD], 0, 3 +1 SD), where -1 to +1 was the referent group. We estimated risk differences and 95% confidence intervals (CIs) via marginal standardization.

RESULTS

We included 1,693 dichorionic twin pregnancies in the cohort. In adjusted analysis, the incidence of preeclampsia increased with increasing early GWG among women with normal BMI. Women with normal BMI and a GWG z-score < - 1 (equivalent to 2.6 kg by 20 weeks) had 2.5 fewer cases of preeclampsia per 100 births (95% CI: -4.7 to - 0.3) compared with the referent; those with GWG z-score > +1 (equivalent to gaining 9.8 kg by 20 weeks) had 2.8 more cases of preeclampsia per 100 (95 % CI: 0.1-5.5) compared with the referent. In adjusted analyses, early GWG had minimal impact on the risk of preeclampsia in women with overweight or obesity.

CONCLUSION

GWG of 2.6 kg or less by 20 weeks was associated with a decreased risk of preeclampsia among women pregnant with dichorionic twins and normal prepregnancy BMI. Current GWG guidelines focus on optimizing fetal weight and gestational length. Our findings demonstrate the importance of considering other outcomes when making GWG recommendations for twin pregnancy.

KEY POINTS

· Early GWG decreased with increasing BMI category.. · Among women with normal weight, as early GWG increased so did the risk of preeclampsia.. · There was no association between early GWG and preeclampsia among women with overweight or obesity..

Weight gain patterns among pregnancies with obesity and small- and large-for-gestational-age births

OBJECTIVE

This case-cohort study estimated associations between gestational weight gain (GWG) and small-for-gestational-age (SGA) and large-for-gestational-age (LGA) births stratified by obesity class (I: 30-34.9 kg/m2 ; II: 35-39.9 kg/m2 ; III: ≥40 kg/m2 ) (Magee-Womens Hospital, Pittsburgh, Pennsylvania, 1998-2011).

METHODS

First-trimester GWG was categorized as being below (<0.2 kg), within (0.2-2.0 kg), or above (>2.0 kg) the Institute of Medicine recommendations. For second- and third-trimester GWG, four linear trajectories were derived: approximating maintenance (slope -0.05 ± 0.03 kg/wk), approximating the recommendations (0.27 ± 0.01 kg/wk; reference), higher than the recommendations (0.54 ± 0.01 kg/wk), and highest among those above the recommendations (0.91 ± 0.02 kg/wk).

RESULTS

For classes I, II, and III, respectively, there were 1290, 1247, and 1198 pregnancies in the subcohort; 262, 171, and 123 SGA cases; and 353, 286, and 257 LGA cases. First-trimester GWG was not associated with SGA/LGA births. Second- and third-trimester weight maintenance was associated with potentially lower LGA risk (risk ratio [RR]: 0.80; 95% confidence interval [CI]: 0.55-1.1) but not higher SGA risk (RR: 0.98; 95% CI: 0.64-1.5) for class III. In addition, some sensitivity analyses supported no increased SGA risk with second- and third-trimester weight maintenance for classes I and II.

CONCLUSIONS

Second- and third-trimester weight maintenance may be associated with more optimal birth weight for gestational age. However, how this could be achieved (e.g., through diet and exercise interventions) is unclear, given the observational design of our study.

Are Detailed Behavioral, Psychosocial, and Environmental Variables Necessary to Control for Confounding in Pregnancy Weight Gain Research?

BACKGROUND

Associations between pregnancy weight gain and adverse outcomes may be spurious owing to confounding by factors not typically measured in cohort studies. We determined the extent to which the addition of detailed behavioral, psychosocial, and environmental measurements to commonly available covariates improved control of confounding.

METHODS

We used data from a prospective US pregnancy cohort study (2010-2013, n = 8978). We calculated two propensity scores for low and high pregnancy weight gain (vs. adequate gain) using 11 standard confounders (e.g., age and education). We examined the balance of characteristics between weight gain groups before and after propensity score matching. We used negative binomial regression to estimate the association between weight gain and small- and large-for-gestational-age birth, preterm birth, and unplanned cesarean delivery, controlling for propensity score. To this model, we then added 17 detailed behavioral, psychosocial, and environmental measurements ("fully adjusted"). We calculated the risk ratio owing to confounding as the ratio of the standard confounder-adjusted risk ratio to the fully adjusted risk ratio.

RESULTS

There were minimal imbalances between weight gain groups in detailed measures after matching for a propensity score of standard covariates. Accordingly, the inclusion of detailed covariates had minimal impact on estimated associations between low or high pregnancy weight gain and adverse pregnancy outcomes: risk ratios owing to confounding were null for all outcomes (e.g., 1.1 [95% CI = 1.0, 1.1] for low weight gain and preterm birth).

CONCLUSIONS

Adjustment for detailed behavioral, psychosocial, and environmental measurements had minimal impact on estimated associations between pregnancy weight gain and adverse perinatal outcomes.

Gestational weight gain in triplet pregnancies in the United States

BACKGROUND

The Institute of Medicine has published national recommendations for optimal pregnancy weight gain ranges for singletons and twins but not for higher-order multiples. A common clinical resource suggests weight gain targets for triplet pregnancies, but they are based on a single, small study conducted over 20 years ago.

OBJECTIVE

We sought to describe contemporary maternal weight gain patterns in triplet gestations in the United States, the weight gain patterns associated with good neonatal outcomes, and how these patterns compare with those of healthy twin pregnancies.

STUDY DESIGN

We used data from 7705 triplet pregnancies drawn from the United States live birth and fetal death files (2012‒2018). We calculated total pregnancy weight gain as weight at delivery minus the prepregnancy weight. A good neonatal outcome was defined as delivery at ≥32 weeks' gestation of 3 liveborn infants weighing ≥1500 g with 5-minute Apgar scores of ≥3. We described the weight gain patterns of triplet pregnancies with good neonatal outcomes by calculating week-specific percentiles of the total weight gain distribution for deliveries at 32 to 37 weeks' gestation. For comparative purposes, we plotted these values against the percentiles of a previously published weight gain chart for monitoring and evaluating twin pregnancies from a referent cohort.

RESULTS

Most participants were over weight (26%) or obese (30%), and 42% were normal weight or underweight. The 50th percentile (25th-75th) of total weight gain in triplet pregnancies was 17 (11-23) kg. As the body mass index category increased, the total weight gain declined: underweight or normal weight, median 19 (14-25) kg; overweight, 17 (12-23) kg; obese, 14 (7.7-20) kg. Approximately 46% of triplet pregnancies had a good neonatal outcome (n=3562). For underweight or normal weight triplet pregnancies with good neonatal outcomes, the 50th percentiles of weight gain at 32 weeks' and 36 weeks' gestation were 12.3 kg and 22.7 kg, respectively. The 10th and 90th percentiles were 12.3 kg and 32.7 kg, respectively, at 32 weeks, and 15.0 kg and 34.1 kg, respectively, at 36 weeks. Triplet pregnancies with prepregnancy overweight or obesity and a good neonatal outcome had lower weight gains. Compared with the reference values for pregnancy weight gain from a twin-specific weight gain chart, the median total weight gain in triplet pregnancies with good neonatal outcomes was approximately 3 to 5 kg more than twins, regardless of body mass index.

CONCLUSION

Our study fills an important gap in understanding how much weight gain can be expected among triplet pregnancies by body mass index category. These descriptive data are a necessary first step to inform science-based triplet gestational weight gain guidelines. Additional research is needed to determine whether monitoring triplet pregnancy weight gain is useful for promoting healthy outcomes for pregnant individuals and children and what targets should be used to optimize maternal and neonatal health.

Gestational Weight Gain and Birth Outcome: A Comparison of Methods of Accounting for Gestational Age

Cross-sectional studies of total gestational weight gain (GWG) and perinatal outcomes have used different approaches to operationalize GWG and adjust for duration of gestation. Using birth records from California (2007-2017), Nevada (2010-2017), and Oregon (2008-2017), we compared 3 commonly used approaches to estimate associations between GWG and cesarean delivery, small-for-gestational-age birth, and low birth weight (LBW): 1) the Institute of Medicine-recommended GWG ranges at a given gestational week, 2) total weight gain categories directly adjusting for gestational age as a covariate, and 3) weight-gain-for-gestational-age z scores derived from an external longitudinal reference population. Among 5,461,130 births, the 3 methods yielded similar conclusions for cesarean delivery and small-for-gestational-age birth. However, for LBW, some associations based on z scores were in the opposite direction of methods 1 and 2, paradoxically suggesting that higher GWG increases risk of LBW. This was due to a greater proportion of preterm births among those with high z scores, and controlling for gestational age in the z score model brought the results in line with the other methods. We conclude that the use of externally derived GWG z scores based on ongoing pregnancies can yield associations confounded by duration of pregnancy when the outcome is strongly associated with gestational age at delivery.

Patterns of gestational weight gain among women with obesity and its correlation with hypertensive disorders of pregnancy in Chinese women

Gestational weight management in obese women is critical in clinical work. Adverse pregnancy outcomes are associated with improper gestational weight gain (GWG). However, the pattern of GWG (PGWG) and its correlation with hypertensive disorders of pregnancy (HDP) in obesity are still unclear in China. This retrospective cohort study evaluates clinical data from 799 women through multivariate analyses and trajectory analyses. All the participants are stratified per first trimester weight gain category into three groups (Inadequate-1st, <0.5 kg; Adequate-1st, 0.5-2.0 kg; Excessive-1st, >2.0 kg) and PGWG refers to the weekly weight gain during each gestational period. GWG is positively associated with first trimester weight gain. 78.4% of the Excessive-1st participants have excessive total GWG, in contrast to Inadequate-1st (32.7%) and Adequate-1st (48.2%). After 20 weeks, the weekly weight gain rapidly accelerates, and 77.3% have a weekly weight gain exceeding the Institute of Medicine recommendations. Trajectory analysis of weekly weight gain based on HDP shows two separate weight gain curves after 20 weeks in women with and without a high risk of HDP. Especially in Excessive-1st participants, weekly weight gain after 20 weeks over 0.32 kg/w is positively related to the risk of HDP (<0.32 kg/w vs. 0.32-0.61 kg/w, adjusted odds ratios [aOR]: 2.999, 95% confidence interval [CI]: 1.054-8.537; <0.32 kg/w vs. >0.61 kg/w, aOR: 5.362, 95% CI: 1.719-16.729). In summary, the first trimester is critical for gestational weight management in obesity. Excessive weight gain during the first trimester and after 20 weeks predicts a high risk of HDP, which should be noted in clinical practice.

Excessive Gestational Weight Gain and Long-Term Maternal Cardiovascular Risk Profile: The Study of Women's Health Across the Nation

Background: Excessive gestational weight gain (GWG) is consistently linked with maternal risk of obesity. However, the literature on its long-term cardiovascular risk is minimal and conflicting. We evaluated whether excessive GWG is associated with a high-risk cardiovascular profile among parous women in midlife. Materials and Methods: Participants were women in the multiethnic cohort Study of Women's Health Across the Nation with a history of live birth(s). Excessive GWG was defined according to Institute of Medicine guidelines and collected by self-recall. Outcomes were the atherosclerotic cardiovascular disease (ASCVD) risk score and C-reactive protein (CRP), measured at the study baseline when mean age was 47 years, and at 10 follow-up visits (1996-2017). We estimated the association of excessive GWG with outcomes through linear mixed model regression. Results: The analytic sample included 1318 women with 3049 singleton births. Over 40% (536) reported one or more pregnancies with excessive GWG. Longitudinal models estimated that at a mean age of 67, women with a history of excessive GWG had a 9.8% (9.2, 10.5) 10-year ASCVD risk, compared to 9.5% (8.9, 10.1) for those without, and mean CRP of 2.20 mg/L (1.89, 2.57) versus 1.85 mg/L (1.61, 2.14), respectively, adjusted for participant characteristics. Conclusions: In this multiethnic cohort of parous women, a history of excessive GWG was associated with a small, but statistically significant difference in ASCVD risk, and a moderate, statistically significant difference in CRP across midlife. More research is necessary to understand the mechanistic pathway between excessive GWG and long-term maternal cardiovascular health.

The association between maternal pre-pregnancy body mass index and pregnancy outcomes of preeclampsia

OBJECTIVE

To evaluate the effects of pre-pregnancy maternal body mass index (BMI) to pregnancy outcomes in patients diagnosed as preeclampsia.

MATERIALS AND METHODS

This was a retrospectively study on women who had been diagnosed as preeclampsia and delivered at Seoul National University Bundang Hospital between June 2017 and March 2020. Multifetal gestation, major fetal anomaly, and fetal death in utero were excluded. A total of 150 singleton pregnancies were included and divided into four groups according to the pre-pregnancy BMI classification: underweight (<18.5 kg/m², n = 6), normal (18.5-22.9 kg/m², n = 66), overweight (23.0-24.9 kg/m², n = 26), and obese (≥25.0 kg/m², n = 52). Pregnancy outcomes including gestational age at delivery, birthweight, and delivery modes were reviewed.

RESULTS

The rates of preterm birth before 34 weeks of gestation were 67%, 49%, 35%, and 27% for underweight group, normal BMI group, overweight group, and obese group, respectively (p-trend = 0.006). The birthweight of newborn increased significantly as pre-pregnancy BMI increased (p-trend<0.001). The proportions of small for gestational age (SGA) were highest in underweight group and decreased as pre-pregnancy BMI increased (67%, 41%, 42%, and 10% for each group, respectively, p-trend<0.001).

CONCLUSION

The rates of preterm birth before 34 weeks and SGA increased as pre-pregnancy BMI decreased in patients with preeclampsia.

IMPLICATIONS FOR PRACTICE

Women with underweight before pregnancy are at the highest risk for preterm birth and SGA, therefore they need to be monitored more intensively when diagnosed as preeclampsia.

Outcomes from a hybrid implementation-effectiveness study of the living well during pregnancy Tele-coaching program for women at high risk of excessive gestational weight gain

Background

Excess gestational weight gain (GWG) is associated with short-term perinatal complications and longer term cardiometabolic risks for mothers and their babies. Dietitian counselling and weight gain monitoring for women at risk of high pregnancy weight gain is recommended by clinical practice guidelines. However, face-to-face appointments, during a time with high appointment burden, can introduce barriers to engaging with care. Telephone counselling may offer a solution. The Living Well during Pregnancy (LWdP) program is a dietitian-delivered telephone coaching program implemented within routine antenatal care for women at risk of excess GWG. This program evaluation used a hybrid implementation-effectiveness design guided by the RE-AIM framework to report on the primary outcomes (reach, adoption, implementation, maintenance) and secondary outcomes (effectiveness) of the LWdP intervention.

Methods

The LWdP program evaluation compared data from women participating in the LWdP program with a historical comparison group (pregnant women receiving dietetic counselling for GWG in the 12 months prior to the study). The primary outcomes were described for the LWdP program. Between group comparisons were used to determine effectiveness of achieving appropriate GWG and pre and post intervention comparisons of LWdP participants was used to determine changes to dietary intake and physical activity.

Results

The LWdP intervention group (n = 142) were compared with women in the historical comparison group (n = 49). Women in the LWdP intervention group attended 3.4 (95% CI 2.9–3.8) appointments compared with 1.9 (95% CI, 1.6–2.2) in the historical comparison group. GWG was similar between the two groups, including the proportion of women gaining weight above the Institute of Medicine recommendations (70% vs 73%, p = 0.69). Within group comparison showed that total diet quality, intake of fruit and vegetables and weekly physical activity were all significantly improved from baseline to follow-up for the women in LWdP, while consumption of discretionary food and time spent being sedentary decreased (all p < 0.05).

Conclusion

The LWdP program resulted in more women accessing care and positive improvements in diet quality, intuitive eating behaviours and physical activity. It was as effective as face-to-face appointments for GWG, though more research is required to identify how to engage women earlier in pregnancy and reduce appointment burden.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12913-022-08002-5.

Gestational Diabetes in Twin Versus Singleton Pregnancies With Normal Weight or Overweight Pre-Pregnancy Body Mass Index: The Mediating Role of Mid-Pregnancy Weight Gain

BACKGROUND

Gestational diabetes might be more common in twin versus singleton pregnancies, yet the reasons for this are unclear. We evaluated the extent to which this relationship is explained by higher mid-pregnancy weight gain within normal weight and overweight pre-pregnancy body mass index (BMI) strata.

METHODS

We analyzed serial weights and glucose screening and diagnostic data abstracted from medical charts for twin (n = 1397) and singleton (n = 3117) pregnancies with normal or overweight pre-pregnancy BMI delivered from 1998 to 2013 at Magee-Womens Hospital in Pennsylvania. We used causal mediation analyses to estimate the total effect of twin versus singleton pregnancy on gestational diabetes, as well as those mediated (natural indirect effect) and not mediated (natural and controlled direct effects) by pathways involving mid-pregnancy weight gain.

RESULTS

Odds of gestational diabetes were higher among twin pregnancies [odds ratios (ORs) for total effect = 2.83 (95% CI = 1.54, 5.19) for normal weight and 2.09 (95% CI = 1.16, 3.75) for overweight pre pregnancy BMI], yet there was limited evidence that this relationship was mediated by mid-pregnancy weight gain [ORs for natural indirect effect = 1.21 (95% CI = 0.90, 1.24) for normal weight and 1.06 (95% CI = 0.92, 1.21) for overweight pre-pregnancy BMI] and more evidence of mediation via other pathways [ORs for natural direct effect = 2.34 (95% CI = 1.24, 4.40) for normal weight and 1.97 (95% CI = 1.08, 3.60) for overweight pre-pregnancy BMI].

CONCLUSIONS

While twin pregnancies with normal weight or overweight pre-pregnancy BMI experienced higher odds of gestational diabetes versus singletons, most of this effect was explained by pathways not involving mid-pregnancy weight gain.

Risk of preeclampsia by gestational weight gain in women with varied prepregnancy BMI: A retrospective cohort study

INTRODUCTION

Despite the important clinical significance, limited data on the joint contribution of prepregnancy body mass index (BMI) and gestational weight gain (GWG) to preeclampsia, the second leading cause of maternal mortality worldwide. This study aimed to estimate the risk of preeclampsia by GWG among women with varied prepregnancy BMI.

METHODS

We conducted a retrospective cohort study using data of 117 738 singleton pregnant women aged 18-49 years from 150 maternity hospitals in China between 2015 and 2018. GWG was calculated as the measured weight at the time of preeclampsia assessment minus prepregnancy weight; GWG velocity was calculated as the GWG divided by the gestational age at weighing. The non-linear associations of GWG with preeclampsia were examined by restricted cubic spline regression analysis according to prepregnancy BMI. The association of the GWG categories with preeclampsia was further examined by performing robust Poisson regression stratified by the prepregnancy BMI categories.

RESULTS

Among participants, 2426 (2.06%) were diagnosed with preeclampsia. Compared to women with normal BMI, those who were overweight and obese had 1.92- fold (95%CI, 1.73-2.14) and 5.06- fold (95%CI, 4.43-5.78) increased risks for preeclampsia, respectively. The association of GWG velocity with preeclampsia was presented as a J-shaped curve with the varied inflexion point (where the rate of preeclampsia was 2%), which was 0.54, 0.38, and 0.25 kg/week in women with normal BMI, overweight, and obesity, respectively; a steep risk rise was observed along with GWG velocity beyond the inflexion points. The overall adjusted relative risk for preeclampsia was calculated among women with the different GWG categories of GWG.

CONCLUSIONS

The findings highlight that high prepregnancy BMI and exceed GWG contributed to increased risk of preeclampsia with a superimposed effect and underscore the need to optimize the recommendations for GWG for women with different prepregnancy BMI.

Prospective evaluation of first-trimester screening strategy for preterm pre-eclampsia and its clinical applicability in China

OBJECTIVES

To evaluate, in a Chinese population, the performance of a screening strategy for preterm pre-eclampsia (PE) using The Fetal Medicine Foundation (FMF)'s competing-risks model and to explore its clinical applicability in mainland China.

METHODS

This was a prospective, multicenter, observational cohort study including 10 899 women with singleton pregnancy who sought prenatal care at one of 13 hospitals, located in seven cities in mainland China, between 1 December 2017 and 30 December 2019. Mean arterial pressure (MAP), uterine artery pulsatility index (UtA-PI) and maternal serum levels of placental growth factor (PlGF) and pregnancy-associated plasma protein-A (PAPP-A) at 11 + 0 to 13 + 6 weeks' gestation were measured and converted into multiples of the median using Chinese reference ranges. Individualized risk for preterm PE was calculated using the FMF algorithm. Prior risk was calculated based on maternal demographic characteristics and obstetric history. We evaluated the efficiency of the screening strategy using various combinations of biomarkers and analyzed its predictive performance for a composite of placenta-associated adverse pregnancy outcomes, including PE, placental abruption, small-for-gestational age (SGA) and preterm birth, at fixed false-positive rates for preterm PE.

RESULTS

We identified 312 pregnancies that developed PE, of which 117 cases were diagnosed as preterm PE (< 37 weeks' gestation). There were 386 pregnancies complicated by severe composite placenta-associated adverse outcome, including preterm PE, 146 cases of severe SGA (birth weight < 3^rd percentile) neonate, 61 cases with placental abruption and 109 cases of early preterm birth < 34 gestational weeks. The triple-marker model containing biomarkers MAP, UtA-PI and PAPP-A achieved, at fixed false-positive rates of 10%, 15% and 20%, detection rates for preterm PE of 65.0%, 72.7% and 76.1%, respectively, and detection rates for severe composite placenta-associated adverse outcome of 34.7%, 41.7% and 46.4%, respectively. Replacing PAPP-A with PlGF or adding PlGF to the model did not improve the performance. Of women screening positive for preterm PE at a fixed 5% false-positive rate, an estimated 30% developed at least one placenta-associated adverse pregnancy outcome, including PE, placental abruption, SGA (birth weight < 10^th percentile) and preterm birth < 37 weeks.

CONCLUSIONS

The FMF competing-risks model for preterm PE was found to be effective in screening a mainland Chinese population. Women who screened positive for preterm PE had increased risk for other placenta-associated pregnancy complications. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Routinely collected antenatal data for longitudinal prediction of preeclampsia in nulliparous women: a population-based study

The objective was to evaluate the sequentially updated predictive capacity for preeclampsia during pregnancy, using multivariable longitudinal models including data from antenatal care. This population-based cohort study in the Stockholm-Gotland Counties, Sweden, included 58,899 pregnancies of nulliparous women 2008-2013. Prospectively collected data from each antenatal care visit was used, including maternal characteristics, reproductive and medical history, and repeated measurements of blood pressure, weight, symphysis-fundal height, proteinuria, hemoglobin and blood glucose levels. We used a shared-effects joint longitudinal model including all available information up until a given gestational length (week 24, 28, 32, 34 and 36), to update preeclampsia prediction sequentially. Outcome measures were prediction of preeclampsia, preeclampsia with delivery < 37, and preeclampsia with delivery ≥ 37 weeks' gestation. The area under the curve (AUC) increased with gestational length. AUC for preeclampsia with delivery < 37 weeks' gestation was 0.73 (95% CI 0.68-0.79) at week 24, and increased to 0.87 (95% CI 0.84-0.90) in week 34. For preeclampsia with delivery ≥ 37 weeks' gestation, the AUC in week 24 was 0.65 (95% CI 0.63-0.68), but increased to 0.79 (95% CI 0.78-0.80) in week 36. The addition of routinely collected clinical measurements throughout pregnancy improve preeclampsia prediction and may be useful to individualize antenatal care.

Comparison of methods for interpolating gestational weight gain between clinical visits in twin and singleton pregnancies

PURPOSE

Researchers are interested in studying longitudinal patterns of gestational weight gain, yet this requires daily/weekly weights, and maternal weight is measured only during prenatal visits. We evaluated the relative accuracy and precision of methods for estimating maternal weight gain between prenatal visits among twin and singleton pregnancies.

METHODS

We analyzed cohorts of dichorionic twin and singleton pregnancies delivered from 1998-2013 in Pittsburgh, Pennsylvania. We mimicked a typical study by retaining pre-pregnancy, first prenatal visit, glucose screening visit, and delivery weights, using these to fit interpolation models, estimating weight throughout pregnancy using 16 different methods, and calculating the difference in kilograms between predicted and measured values among remaining weights. We evaluated the performance of each model by calculating root mean squared error (RMSE).

RESULTS

RMSE ranged from 1.55 to 6.09 kg in twins (n = 2067) and 1.45 to 4.87 kg in singletons (n = 7331). The most accurate and precise methods incorporated restricted cubic splines, random intercepts and slopes for pregnancy, and internal knots demarcating trimesters/quantiles (RMSE = 1.55/1.56 kg in twins, 1.45/1.45 kg in singletons), while individual-level linear interpolation between proximal measurements also performed well.

CONCLUSIONS

Accuracy and precision of methods for estimating maternal weight gain between measurements differed by model, and were best among individually-tailored and flexible models.

A systematic review of quantitative bias analysis applied to epidemiological research

BACKGROUND

Quantitative bias analysis (QBA) measures study errors in terms of direction, magnitude and uncertainty. This systematic review aimed to describe how QBA has been applied in epidemiological research in 2006-19.

METHODS

We searched PubMed for English peer-reviewed studies applying QBA to real-data applications. We also included studies citing selected sources or which were identified in a previous QBA review in pharmacoepidemiology. For each study, we extracted the rationale, methodology, bias-adjusted results and interpretation and assessed factors associated with reproducibility.

RESULTS

Of the 238 studies, the majority were embedded within papers whose main inferences were drawn from conventional approaches as secondary (sensitivity) analyses to quantity-specific biases (52%) or to assess the extent of bias required to shift the point estimate to the null (25%); 10% were standalone papers. The most common approach was probabilistic (57%). Misclassification was modelled in 57%, uncontrolled confounder(s) in 40% and selection bias in 17%. Most did not consider multiple biases or correlations between errors. When specified, bias parameters came from the literature (48%) more often than internal validation studies (29%). The majority (60%) of analyses resulted in >10% change from the conventional point estimate; however, most investigators (63%) did not alter their original interpretation. Degree of reproducibility related to inclusion of code, formulas, sensitivity analyses and supplementary materials, as well as the QBA rationale.

CONCLUSIONS

QBA applications were rare though increased over time. Future investigators should reference good practices and include details to promote transparency and to serve as a reference for other researchers.

Weight Gain Before the Third Trimester and Risk of Hypertensive Disorders of Pregnancy: A Prospective Cohort Study

BACKGROUND The association between excessive gestational weight gain (GWG) and the risk of hypertensive disorders of pregnancy (HDP) remains uncertain in women with increased water retention in late gestation associated with the pathophysiology of HDP. This study aimed to investigate the association between GWG before the third trimester and the risk of HDP. MATERIAL AND METHODS This was a prospective cohort study in singleton-pregnant women in Tianjin, China, from 2016. Generalized linear models were used to analyze the relationship between weight gain and the risk of HDP. RESULTS A total of 5295 singleton-pregnant women were included. Even after adjusting for relevant confounders, weight gain at approximately 28 weeks remained an independent risk factor for HDP in the normal-weight group. Compared to the reference of low weight gain (+1 SD was associated with an approximately 2.0 times greater likelihood of HDP (RR: 2.08, 95% CI: 1.06-4.08). Moreover, there was a positive relationship between weight gain in the short interval of early pregnancy and risk of HDP in overweight women. CONCLUSIONS Excessive weight gain before the third trimester was associated with a greater risk of developing HDP among women with early-pregnancy normal weight, which may provide a chance to identify subsequent hypertensive disorders. Additional research is needed to determine whether early-pregnancy weight gain is associated with HDP risk.

Weight gain during pregnancy and the risk of severe maternal morbidity by prepregnancy BMI

BACKGROUND

High and low prepregnancy BMI are risk factors for severe maternal morbidity (SMM), but the contribution of gestational weight gain (GWG) is not well understood.

OBJECTIVES

We evaluated associations between GWG and SMM by prepregnancy BMI group.

METHODS

We analyzed administrative records from 2,483,684 Californian births (2007-2012), utilizing z score charts to standardize GWG for gestational duration. We fit the z scores nonlinearly and categorized GWG as above, within, or below the Institute of Medicine (IOM) recommendations after predicting equivalent GWG at term from the z score charts. SMM was defined using a validated index. Associations were estimated using multivariable logistic regression models.

RESULTS

We found generally shallow U-shaped relations between GWG z score and SMM in all BMI groups, except class 3 obesity (≥40 kg/m2), for which risk was lowest with weight loss. The weight gain amount associated with the lowest risk of SMM was within the IOM recommendations for underweight and class 2 obesity, but above the IOM recommendations for normal weight, overweight, and class 1 obesity. The adjusted risk ratios (RRs) and 95% CIs for GWG below the IOM recommendations, compared with GWG within the recommendations, were the following for underweight, normal weight, overweight, class 1 obesity, class 2 obesity, and class 3 obesity: 1.13 (0.99, 1.29), 1.09 (1.04, 1.14), 1.10 (1.01, 1.19), 1.07 (0.95, 1.21), 1.03 (0.88, 1.22), and 0.89 (0.73, 1.08), respectively. For GWG above the recommendations, the corresponding RRs and 95% CIs were 0.99 (0.84, 1.15), 1.04 (0.99, 1.08), 0.98 (0.92, 1.04), 1.03 (0.95, 1.13), 1.07 (0.94, 1.23), and 1.08 (0.91, 1.30), respectively.

CONCLUSIONS

High and low GWG may be modestly associated with increased risk of SMM across BMI groups, except in women with class 3 obesity, for whom low weight gain and weight loss may be associated with decreased risk of SMM.