Misreport of Gestational Weight Gain (GWG) in Birth Certificate Data

Abstract

Birth certificates are potentially a valuable source of information for studying gestational weight gain (GWG) during pregnancy, particularly important given new Institute of Medicine (IOM) guidelines. We examined factors associated with the accuracy of maternal GWG self-report by linking the gold standard obstetric electronic medical record (EMR) of women from a large urban practice to state birth certificates. Primary outcomes included maternal under-reporting of GWG (>10 lbs below the EMR), accurate reporting (within 10 lbs), and over-reporting (>10 lbs above EMR). Data were stratified across categories of pre-pregnancy body mass index (BMI) and the actual GWG IOM categories (inadequate, adequate, and excessive) acquired in the clinical setting and recorded in the EMR. Among 1,223 women, mean (SD) age was 27.4 (6.2) years, mean (SD) BMI was 28.2 (8.1) kg/m(2), and mean GWG was 26.0 (20.2) pounds. The majority of women with normal BMI (<25 kg/m(2)) and adequate GWG reported GWG accurately (78.8%), more so than any other group. After adjusting for age, race, insurance status, and number of prenatal visits, among women with actual adequate GWG, women with high BMI (≥25 kg/m(2)) were more likely to over-report GWG than women with normal BMI (RR 4.7, 95% CI 2.6-8.4). In patients with normal BMI, women with excessive GWG were more likely to under-report than women with adequate GWG (RR 6.0, 95% CI 3.0-12.1). Such findings raise concern for systematic bias that would limit the use of birth certificate data for studying population trends in GWG.

Validity of birth certificate‐derived maternal weight data in twin pregnancies

“…These factors could lead to important differences in the accuracy of maternal weight data on birth certificates. Nevertheless, our study suggests that the degree of error is similar to what we and others previously observed among singletons (Bodnar et al 2014) (Vinikoor et al 2010; Park et al 2011; Wright et al 2012). …”

Pre‐pregnancy body mass index, weight change during pregnancy, and risk of intellectual disability in children

“…52 In a smaller, clinic-based study, Wright et al found that gestational weight gain recorded in birth certificates was within 4.5 kg for 48% of women, whereas 52% had weight gain either over-or under-reported by at least 4.5 kg. 53 For the misreporting of BMI to have accounted for the findings of this study, a systematic relationship between maternal misreporting and the odds of child ID would be needed. Rothman describes how non-differential misclassification can result in a bias away from the null if the exposure variable is continuous (like BMI).…”

“…1 Limitation in intellectual ability corresponds to an intelligence quotient (IQ) of <70, described as mild (IQ 55-70), moderate (IQ [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55], or severe to profound (IQ of <40). 2 The prevalence of ID in the general population is estimated to be approximately 1%, and among those with ID 85% are characterised as having mild ID.…”

Association of trimester-specific gestational weight gain with fetal growth, offspring obesity, and cardiometabolic traits in early childhood

“…A limitation is that maternal pre-pregnancy weight and total GWG were self-reported, which might have led to misclassification. However, studies have shown that recall of pre-pregnancy BMI and GWG is reproducible and valid (46) and underreporting of GWG, which tends to be more frequent than over-reporting, would most likely bias estimates toward the null (47, 48). We were not able to disentangle the effects of 2 nd and 3 rd trimester GWG, as we had no data on maternal weight at the end of the 2 nd trimester of pregnancy.…”