Prediction of large-for-gestational-age infants in pregnancies complicated by obesity: A population-based cohort study

Introduction Infants born large for gestational age (LGA) have increased risks of adverse perinatal outcomes. Maternal obesity, defined as body mass index (BMI) >= 30 kg/m(2), is one of the most prevalent risk factors for LGA and the proportion of pregnancies complicated by obesity is increasing. Early identification of women with BMI >= 30 kg/m(2) at increased risk of giving birth to an LGA infant may open possibilities for prevention, aiming at decreasing the incidence of LGA. Material and methods A population-based cohort study using information from the first-trimester screening database, which was cross-linked with the Swedish Medical Birth Register. The database included 139 277 full-term singletons without fetal anomalies born between 2006 and 2015 to mothers without prepregnancy diabetes. Of these, 9.1% (n = 12 704) were infants of mothers with BMI >= 30 kg/m(2). For all women with BMI >= 30 kg/m(2), a prediction model for LGA to be used in early pregnancy was constructed based on information on biochemical markers and maternal characteristics. A similar model, as well as a prepregnancy prediction model, were constructed for parous women with BMI >= 30 kg/m(2). In parous women, data from the previous pregnancy were also used. Receiver operating characteristic curve and area under curve (AUC) were calculated. Results The predictive models for LGA in parous women with BMI >= 30 kg/m(2) prepregnancy and in early pregnancy had AUCs of 0.80 (95% CI 0.78-0.82) and 0.81 (95% CI 0.79-0.82), respectively. For all women with BMI >= 30 kg/m(2), the prediction of LGA in early pregnancy had an AUC of 0.66 (95% CI 0.64-0.67). Conclusions Performance of the prepregnancy and early pregnancy prediction models for LGA in parous women with BMI >= 30 kg/m(2) was good. The predictive capacity was largely driven by previous child's birthweight. First-trimester measurements of fetal size did not improve the predictive capacity in parous women. Predictions of LGA in all women with BMI >= 30 kg/m(2) in early pregnancy, without taking previous child's birthweight into account, remain difficult.