Objective: To compare the actual maternal weight gain to that recommended by the Institute of Medicine (IOM) in term singleton gestations.
Methods: We used data from the Slovenian National Perinatal Information System to select singleton pregnancies born at ≥38 weeks during the period from 2003 to 2012. We calculated the frequencies of mothers who gained less than, more than, and as recommended by the IOM according to their pregravid body mass index (BMI). We also compared the fetal size parameters in under- and over-gainer to those who gained weight as recommended by the IOM.
Results: We selected 173,715 patients who delivered at ≥38 weeks. Of these patients, the recommended weight gain was achieved by 56,868 (32.7%, 95% CI 32.5, 32.9) only, 82,617 (47.6%, 95% CI 47.3, 47.8) were over-gainers, and 34,230 (19.7%, 95% CI 19.5, 19.8) gained less than recommended. Neither undergaining nor overgaining were always synonymous with adverse fetal outcomes.
Conclusions: Roughly two-thirds of singleton mothers did not gain weight during pregnancy according to the IOM recommendations. Inappropriate maternal weight gain, however, was not always associated with adverse fetal outcomes and this implies that a tailored approach rather than strict adherence to the IOM recommendations may be more practical.