Is obesity in pregnancy associated with signs of chronic fetal hypoxia

INTRODUCTION The prevalence of obesity in pregnancy is increasing world-wide. Maternal obesity increases risks of severe fetal and neonatal complications. The underlying pathophysiological mechanisms are unclear. One possible contributing factor could be chronic fetal hypoxia. The aim of this study was to compare placentas from women with and without obesity with respect to placental lesions which could reflect compensatory mechanisms in response to chronic fetal hypoxia as well as lesions possibly leading to chronic fetal hypoxia. In addition, levels of erythropoietin in cord blood were compared between offspring of lean and obese women. MATERIAL AND METHODS This cohort study included 180 women with uneventful, full-term, singleton pregnancies, out of which 91 lean women with body mass index (BMI; kg/m2 ) 18.5-24.9 and 89 women with obesity; BMI ≥30. Women were recruited at Sodersjukhuset between 16 October 2018 and 2 December 2019. Placentas were investigated by two senior perinatal pathologists, who were blinded for maternal BMI. Cord blood was analyzed for levels of erythropoietin. RESULTS Levels of erythropoietin in cord blood increased with maternal BMI (P-value 0.01, β= 0.97, CI: 0.27 - 1.68). There was no difference between placentas of obese and lean women in number of placental lesions reflecting chronic fetal hypoxia or in lesions which could possibly lead to chronic fetal hypoxia. CONCLUSIONS This study of term and uneventful pregnancies demonstrated a positive association between maternal obesity and concentrations of erythropoietin in cord blood at birth. This finding supports the hypothesis of chronic fetal hypoxia as a risk factor for complications in obese pregnancies. There were no differences in lesions associated with hypoxia between placentas of obese and lean women.