Pregnancy weight gain by gestational age and stillbirth: a population‐based cohort study

Abstract

ObjectiveTo study the association between total and early pregnancy (<22 completed weeks) weight gain and risk of stillbirth, stratified by early‐pregnancy body mass index (BMI).DesignPopulation‐based cohort study.SettingStockholm‐Gotland Region, Sweden.PopulationPregnant women with singleton births (n = 160 560).MethodsPregnancy weight gain was standardised into gestational age‐specific z‐scores. For analyses of total pregnancy weight gain, a matched design with an incidence density sampling approach was used. Findings were also contrasted with current Institute of Medicine (IOM) weight gain recommendations.Main outcome measuresStillbirth defined as fetal death at ≥22 completed weeks of gestation.ResultsFor all BMI categories, there was no statistical association between total or early pregnancy weight gain and stillbirth within the range of a weight gain z‐score of −2.0 SD to +2.0 SD. Among normal‐weight women, the adjusted odds ratio of stillbirth for lower (−2.0 to −1.0 SD) and higher (+1.0 to +1.9 SD) total weight gain was 0.85 (95% CI; 0.48–1.49) and 1.03 (0.60–1.77), respectively, as compared with the reference category. Further, there were no associations between total or early pregnancy weight gain and stillbirth within the range of weight gain currently recommended by the IOM. For the majority of the BMI categories, the point estimates at the extremes of weight gain values (<−2.0SD and ≥2.0 SD) suggested protective effects of low weight gain and increased risks of high weight gain, but estimates were imprecise and not statistically significant.ConclusionWe found no associations between total or early pregnancy weight gain and stillbirth across the range of weight gain experienced by most women.Tweetable abstractThere was no association between weight gain during pregnancy and stillbirth among most women.

Gestational weight gain and adverse pregnancy outcomes: a prospective cohort study

“…This method ensured that the weight gain of women who experience adverse pregnancy outcomes would be compared with the weight gain of women without adverse outcomes at the same point in pregnancy. 14 21 …”

“…Subjects were excluded if: (1) weight in early pregnancy <30 kg or >350 kg or (2) z-score of GWG <−4.0 or >4.0, the methods used in the study were similar to the study conducted by Johansson et al . 14 Women with pre-existing medical conditions such as pregestational diabetes, hypothyroidism or hyperthyroidism (affecting GWG) 15 and heart/liver/kidney diseases were also excluded.…”

“…The eligible data collected in this study were obtained from: (1) self-reported prepregnancy weight (kg), (2) weight and height (cm) measured in early pregnancy (17 weeks of gestation or less) and (3) weight measured within the last week of pregnancy. Subjects were excluded if: (1) weight in early pregnancy <30 kg or >350 kg or (2) z-score of GWG <−4.0 or >4.0, the methods used in the study were similar to the study conducted by Johansson et al 14 Women with pre-existing medical conditions such as pregestational diabetes, hypothyroidism or hyperthyroidism (affecting GWG) 15 and heart/liver/kidney diseases were also excluded.…”

Response regarding “Good practices for observational studies of maternal weight and weight gain during pregnancy”

“…In a recent population-based study of pregnancy weight gain and stillbirth in 160 560 deliveries in Sweden, we found that the measurement-to-delivery interval is systematically shorter among deliveries at younger gestational ages (when adverse outcomes such as stillbirths are more likely to occur) than among term deliveries. 4 Unpublished analyses from our cohort from Magee-Women’s Hospital in Pittsburgh, PA, 5 suggests similar general trends, although the magnitude of the difference appears smaller.…”

“…For example, in the Swedish cohort analysis, we altered the research plan to use a nested case-control design, where weight measurements for controls were drawn from the cohort of ongoing pregnancies at the time of each stillbirth and matched based on the interval between delivery and last measured weight of the stillbirth (which was then used in subsequent analyses). 4…”