Hautakangas T, et al. - Researchers compared primiparous term pregnancies, one leading to vaginal delivery (VD) vs the other to acute cesarean section (CS) due to labor dystocia in the first stage of labor, in order to assess the influence of body mass index (BMI) on CS risk. Women ending with acute CS were older, shorter and more frequently had a chronic disease. These women had fetal malposition and chorioamnionitis more commonly, less often labor in an active phase and the cervix not as well ripened on arrival at the birth unit. Findings suggest labor dystocia is a multifactorial phenomenon in which the possibility to ameliorate the condition via medical treatment is limited. They recommended hospital admission at an advanced stage of labor. The substantial association of high BMI with labor dystocia suggest the essentiality of pre-pregnancy weight control in the population at reproductive age.

Methods

• Researchers performed a retrospective case-control study in a tertiary delivery unit with 5200 deliveries annually.
• In this study, 296 term primiparous women whose intended vaginal labor ended in acute CS because of dystocia comprised the cases.
• Primiparas with successful vaginal delivery [VD (n=302)] comprised the controls.
• Medical records were used to retrieve the data.
• The associations between BMI and covariates on labor dystocia were assessed using multiple logistic regression analyses.

Results

• Women ending with acute CS were older (OR 1.06 [1.03–1.10]), shorter (OR 0.94 [0.91–0.96]) and more often had a chronic disease (OR 1.60 [1.1–2.29]).
• These women had fetal malposition (OR 42.0 [19.2–91.9]) and chorioamnionitis (OR 10.9 [5.01–23.6]) more commonly, less often labor in an active phase (OR 3.37 [2.38–4.76]) and the cervix not as well ripened (1.5 vs 2.5 cm, OR 0.57 [0.48–0.67] on arrival at the birth unit.
• The dystocia group had higher BMI (24.1 vs 22.6 kg/m², p < 0.001).
• A strong association between rising maternal pre-pregnancy BMI with dystocia risk was noted.
• The risk of CS increase by 10% in association with BMI increase of 1 kg/m².
• Premature rupture of membranes, chorioamnionitis and induction of labor were more common among obese primiparas.
• Less often labors in an active phase were noted for these women at hospital admission.
• Four hours longer labor was observed for severely obese primiparas (BMI≥35 kg/m²) than normal-weight parturients.