Association of objectively measured physical fitness during pregnancy with maternal and neonatal outcomes. The GESTAFIT Project.

Aim: To analyse i) the association of physical fitness during early second trimester and late pregnancy with maternal and neonatal outcomes; and ii) to investigate whether physical fitness is associated with the type of birth (vaginal or caesarean section).

Methods: Pregnant women from the GESTAFIT Project (n = 159) participated in this longitudinal study. Maternal physical fitness including upper- and lower-body strength, cardiorespiratory fitness (CRF) and flexibility were measured through objective physical fitness tests at the 16th and 34th gestational weeks. Maternal and neonatal outcomes were collected from obstetric medical records. Umbilical arterial and venous blood gas pH and partial pressure of carbon dioxide (PCO2) and oxygen (PO2), were assessed.

Results: At the 16th week, greater upper-body muscle strength was associated with greater neonatal birth weight (r = 0.191, p<0.05). Maternal flexibility was associated with a more alkaline arterial pH (r = 0.220, p<0.05), higher arterial PO2 (r = 0.237, p<0.05) and lower arterial PCO2 (r = -0.331, p<0.01) in umbilical cord blood. Maternal CRF at the 16th gestational week was related to higher arterial umbilical cord PO2 (r = 0.267, p<0.05). The women who had caesarean sections had lower CRF (p<0.001) at the 16th gestational week and worse clustered overall physical fitness, both at the 16th (-0.227, p = 0.003, confidence interval (CI): -0.376, -0.078) and 34th gestational week (-0.223; p = 0.018; CI: -0.432, -0.015) compared with the women who had vaginal births.

Conclusion: Increasing physical fitness during pregnancy may promote better neonatal outcomes and is associated with a decrease in the risk of caesarean section. This trial was registered at ClinicalTrials.gov (NCT02582567) on October 20, 2015.