[Maternal underweight and perinatal outcomes: a restrospective cohort study].

Introduction

Some studies have linked maternal underweight with adverse perinatal outcomes such as spontaneous abortion, abruptio placentae, small for gestational age newborn, intrauterine growth retardation and preterm birth.

Objective

To determine the influence of maternal underweight in the onset of labor, route of delivery, birth weight, Apgar score and preterm birth.

Methods

Retrospective cohort study. We included pregnant women from the Hospital Universitario de Puerto Real. Period of study: 2002-2011. Study group: underweight at the beginning of gestation (BMI < 18.5 kg/m2). Control group: pregnant women with normal body mass index (BMI) at the beginning of gestation (18.5-24.9 kg/m2). The risk (OR) of induction of labor, cesarean section, small for gestational age newborn, macrosomia, 5’ Apgar score < 7, and preterm birth was calculated.

Results

The prevalence of underweight was 2.5% versus 58.9% of pregnant women who had a normal BMI. We found no significant differences in the rate of induction of labor, fetal macrosomia, Apgar at 5’ < 7 or preterm delivery. Maternal underweight was associated with a decreased risk of caesarean section (adjusted OR 0.45, 95% CI 0.22 to 0.89) and an increased risk of small for gestational age newborn (adjusted OR 1.74; 95% CI 1.05 to 2.90).

Conclusions

Maternal underweight at the start of pregnancy is associated with a lower risk of caesarean section and a greater risk of small for gestational age newborns (birth weight < P10).