Pre-pregnancy Body Mass Index, Gestational Weight Gain, and Other Maternal Characteristics in Relation to Infant Birth Weight

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Abstract
Objectives Infant birth weight is influenced by modifiable maternal pre-pregnancy behaviors and characteristics. We evaluated the relationship among pre-pregnancy body mass index (BMI), gestational weight gain, and infant birth weight, in a prospective cohort study. Methods Women were enrolled at ≤20 weeks gestation, completed in-person interviews and had their medical records reviewed after delivery. Infant birth weight was first analyzed as a continuous variable, and then grouped into Low birth weight (LBW) (Results Pre-pregnancy BMI was independently and positively associated with infant birth weight (β = 44.7, P = 0.001) after adjusting for confounders, in a quadratic model. Gestational weight gain was positively associated with infant birth weight (β = 19.5, P < 0.001). Lower infant birth weight was associated with preterm birth (β = −965.4, P < 0.001), nulliparity (β = −48.6, P = 0.015), and female babies (β = −168.7, P < 0.001). Less than median gestational weight gain was associated with twice the risk of LBW (RR = 2.04, 95% CI 1.34–3.11). Risk of macrosomia increased with increasing pre-pregnancy BMI and gestational weight gain (P for linear trend Conclusions These findings support the need to balance pre-pregnancy weight and gestational weight gain against the risk of LBW and macrosomia among lean and obese women, respectively.

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