Pregnancy outcomes related to gestational weight gain in women defined by their body mass index, parity, height, and smoking status.

BACKGROUND: Recommendations for gestational weight gain (GWG) account for a woman's prepregnancy body mass index (BMI), but other factors may be important.
OBJECTIVES: The objectives were to investigate whether, within BMI categories, the GWG with the lowest risks to mother and infant varied with parity and to describe these risks in short (<160 cm), young (<20 y), and smoking women.
DESIGN: Of 27,030 primiparous and 31,407 multiparous women with term births within the Danish National Birth Cohort, self-reported GWG was divided into 6 categories (<5, 5-9, 10-15, 16-19, 20-24, and > or =25 kg). Population-based registers provided information about birth outcomes. GWG-specific absolute adjusted risks for emergency cesarean delivery, birth of a small-for-gestational-age (SGA) or large-for-gestational-age (LGA) infant, and postpartum (6 mo) weight retention (PPWR) were compared across different types of women.
RESULTS: The risk of SGA decreased with increasing GWG in both parity groups, but SGA risk <10% was reached at 2-3 GWG categories lower in multiparae than in primiparae. An excess risk of LGA was present only in obese primiparae and multiparae, but the PPWR risk increased with increasing GWG irrespective of BMI and parity. Young primiparae had better outcomes than other primiparae. Short women had a higher risk of emergency cesarean delivery that varied minimally with GWG. Smokers had a higher SGA risk and had a PPWR risk similar to that of nonsmokers.
CONCLUSIONS: The tradeoff in risk between mother and infant is reached at lower GWG in multiparae than in primiparae; therefore, a lower GWG may be needed among multiparae. Differential guidelines seem unnecessary for short or young women or smokers.