Gestational weight gain according to pre-pregnancy body mass index of a group of Latin American adolescents and its association with newborn birth weight.

This study aims to analyze the distribution of gestational weight gain in a group of Latin American adolescents according to their pre-pregnancy body mass index (BMI, based on the World Health Organization criteria for adolescents and adults) and its association with their newborns' birth weight. This longitudinal retrospective study used secondary data from national or institutional perinatal information systems about pregnant adolescents from Argentina, Colombia, Mexico, Panama, Paraguay, and Uruguay. The degree of agreement between the two classification criteria for the pre-pregnancy BMI was determined with the B statistic and the Bangdiwala graph. The association of newborns' weight with the pre-pregnancy BMI and the gestational weight gain was assessed using regression models. This study included 6,141 pregnant adolescents. When compared to the adolescents' criterion, the pre-pregnancy BMI classification for adults tends to underestimate the assigned category, leading to a higher recommended weight gain. Regardless of the criterion, overweight and high gestational weight gain were significantly associated with a higher probability of newborns with macrosomia and birth weight > P90, obesity was associated with birth weight > P90, and low weight gain was associated with low, insufficient, and < P10 birth weight. In conclusion, pre-pregnancy BMI and gestational weight gain are associated with the birth weight of newborns from Latin American adolescents.