[Relationship between maternal body mass index, gestational weight gain and birth weight; prospective study in a health department].

OBJECTIVES: To ascertain the relationship between maternal weight gain and birth weight, in every pre-gestational body mass index (BMI) category.

MATERIAL AND METHODS: A two-stage sampling observational and descriptive study was carried out in the health department of La Ribera (Valencia, Spain). The sample was divided into four groups according to pre-gestational BMI.

FINDINGS: 140 pregnant women were studied. We observed rising pre-gestational weight gain (PWG) and trimestral gradients. There was a higher increase from the first to the second trimester than from the second to the third trimester in every pre-gestational BMI category. According to the international recommendations of Institute of Medicine, 16.4% of women had an inferior gestational weight gain (GWG), 38.6% were within the recommendations and 45% were above them. The pre-gestational BMI, categorized by the WHO, is related to the birth weight, showing a statistical significance (F=6.636 and and p<0.001). Obese mothers with a higher weight gain than the recommended have newborns with higher birth weight (4,353 ± 821.924 g) and, underweight mothers with a lower weight gain than the recommended, have newborns with lower birth weights (2,900 ± 381.83 g) than the rest of the groups.

CONCLUSIONS: The absolute gestational weight gain did not show a statistical significance compared to the birthweight in any of the pre-gestational BMI categories and, as an isolated indicator, is not an added value to the prenatal quality control.