Impact of maternal underweight on obstetric and neonatal prognosis: A retrospective study

Maternal underweight (BMI < 18.5) is an uncommon situation with potentially serious obstetric consequences, though data in the literature are scarce.

To compare the obstetrical prognosis of patients with normal BMI and BMI < 18.5.

We performed a retrospective study in France (Normandy).

We included 14,246 patients between January 2011 and November 2017, among whom 12,648 (88.8 %) had normal BMI, 1269 were considered mild underweight (17 ≤ BMI < 18.5 kg/m²) and 329 (2.3 %) were considered severe to moderate underweight (BMI < 17 kg/m²). The risk of preterm birth was all the greater as the thinness was severe (ORa: 1.34 [1.12-1.60] and ORa 1.77 [1.31-2.34]) and the risk of intrauterine growth retardation also increased with severe thinness (ORa: 1.63 [1.35-1.96] and ORa 2.28 [1.69-3.07]). The risk of a caesarean section or scheduled labour was no different. Neonatal parameters were comparable between the groups.

Our study confirms an increased risk of preterm delivery and intrauterine growth retardation with increased thinness after adjusting for confounding factors. This link had only been shown previously in 2 studies Neither the type of prematurity (induced or spontaneous) nor the severity of prematurity is influenced by the severity of thinness; however, the low prevalence of thinness limits the power of these data. It would be interesting to study the medico-economic relevance of a policy of close maternal-foetal surveillance in this target population.