Early maternal weight gain as a risk factor for SGA in pregnancies with hyperemesis gravidarum: a 15-year hospital cohort study

Inadequate maternal weight gain increases the risk of small-for-gestational age (SGA) infants. Women with hyperemesis gravidarum (HG) are at risk of significant early pregnancy weight loss and insufficient total pregnancy weight gain. Recent studies have implied that weight gain during the first half of pregnancy is more crucial to pregnancy outcome than total weight gain.

The aim of this study was to investigate whether not regaining prepregnancy weight by 13–18 weeks of gestation contributed to not reaching minimum body mass index (BMI)-specific total pregnancy weight gain and influenced the risk of SGA outcome in HG pregnancies.

In this retrospective 15-year cohort (2002–2016) of women hospitalized due to hyperemesis gravidarum, we reviewed individual patient hospital files and corresponding outpatient maternity records to collect prepregnancy BMI and weight, pregnancy weight gain (spanning 3-week intervals), delivery weight and foetal outcomes. BMI and total pregnancy weight gain goals were categorized according to the Institute of Medicine (IOM) 2009 guidelines: BMI < 18,5 kg/m²: 12.5–18 kg, 18.5–24.9 kg/m²: 11.5–16 kg, 25–29.9 kg/m²: 7–11.5 kg and ≥ 30 kg/m²: 5–9 kg. Birth weight was categorized as SGA if less than the 10th percentile of sex- and gestational length-specific Norwegian neonatal weight charts. Nonparametric tests were used to compare weight categories, and logistic regression was used to predict the odds ratio (OR) of inadequate total pregnancy weight gain or SGA delivery.

Out of 892 women hospitalized for HG during 2002–2016, 784 had a pregnancy lasting ≥ 24 weeks, of which 746 were singleton pregnancies with follow-up until delivery. Among these women, 42 were classified as underweight, 514 as normal weight, 230 as overweight and 102 as obese before pregnancy. Not regaining prepregnancy weight by week 13–18 was an independent predictor of inadequate total gestational weight gain with an OR of 7.05 (95% CI 4.24–11.71) and an independent predictor for SGA outcome with an OR of 2.66 (95% CI 1.11–6.34), even when adjusted for total pregnancy weight gain, prepregnancy BMI, parity, age and smoking status.

Inadequate total maternal weight gain and not regaining prepregnancy weight by week 13–18 may be considered independent risk factors for delivering a baby that is small for gestational age in pregnancies with hyperemesis gravidarum. Achieving adequate weight gain during the first trimester in HG pregnancies is important for the foetal outcome, underscoring the importance of nutritional treatment during this period.