148: Joint hypermobility is associated with improved labor outcomes in the second stage


      Connective tissue laxity affects athletic and orthopedic performance. Our objective was to determine if joint hypermobility, as measured by the thumb-to-forearm flex-test (Flex) was associated with labor outcomes and cesarean section.

      Study Design

      Nulliparous women with singleton gestations were prospectively enrolled in this IRB-approved observational study. The Flex Test was assessed in clinic by trained providers. A positive test achieves contact between the dominant ipsilateral thumb and forearm without pain. Clinicians were blinded to the results. Primary outcomes were duration of active phase and second stage, and mode of delivery. Secondary outcomes included prematurity, hemorrhage, and lacerations. Univariate comparisons were made with Pearson Chi square, and Mann-Whitney U test. Significance was set at p<0.05.


      Of 195 subjects, delivery data was available and complete for 163. The mean age was 23.3 yrs (SD 6.4) and the mean gestational age was 39.6 weeks (SD 1.6). 38 required cesarean section (23%). 60 subjects (37%) were Flex +. Among subjects who delivered vaginally, the median duration of the second stage of labor was shorter for Flex + than for Flex - subjects (31 vs 66 minutes, p=0.007). There was no difference in the duration of the total labor (6.2 vs. 6.3 hours, p=0.81) or in the overall rate of cesarean section between Flex+ and Flex- subjects (20 vs 25%, p=0.44). The rate of cesarean for dystocia, however, was lower in Flex + than in Flex - women (33% vs. 77%, p=0.01). There were no significant differences between groups in the risk for preterm labor, hemorrhage, or lacerations. After controlling for gestational age, birth weight and regional anesthesia, FlexTest + was still associated with a shorter second stage of labor (- 15 minutes, +/− 6, p=0.01).


      Connective tissue laxity, as measured by the thumb-to-forearm Flex Test, is a modest predictor of obstetrical labor outcomes, and may identify women at lower risk of cesarean for dystocia in the second stage. Mechanisms for this association deserve further investigation.