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41In vitro human myometrial contractility in pregnancies complicated with obesity

      Objective

      The onset of parturition in pregnant women with obesity is frequently delayed. Without induction, these women are nearly twice as likely as normal-weight women to have prolonged pregnancies. Obesity has been shown to be an independent risk factor for cesarean birth, even after controlling for birth weight. It has been suggested that myometrial contractility is impaired in women with obesity. In this study we aimed to investigate whether contractility is truly reduced in women with obesity compared to their normal-weight counterparts utilizing an in vitro experiment model.

      Study Design

      Myometrial strips alongside the upper part of the low transverse uterine incisions were obtained at the time of the cesarean birth from 22 healthy, non-laboring, pregnant women, scheduled for elective cesarean birth at term. Strips were transferred to the laboratory and underwent dissection into tissue samples, each approximately 5 mm long, 2 mm wide, and 1 mm thick. In isolated muscle tissue baths, each tissue was attached to a stationary hook and the other end was attached to a force transducer and mounted for isometric recording under 2 gm of tension. Tissues were prepared under isometric conditions and underwent both spontaneous and oxytocin-induced contractions. Control experiments were performed simultaneously.

      Results

      Total of 11 participants with obesity and 11 normal-weight participants were enrolled. In both spontaneous and oxytocin-induced contractions, there was a significant reduction in amplitude of contractions between normal-weight and participants with obesity (P= 0.04, and P=0.049 in spontaneous and oxytocin-induced contractions respectively) and a significant reduction in frequency of contractions between groups (P= 0.01, and P=0.02 in spontaneous and oxytocin-induced contractions respectively).

      Conclusion

      Obesity may impair the ability of the uterus to contract in labor which might contribute to the increased cesarean birth rate in women with obesity. This study reiterates the importance of preconception counseling on optimizing weight prior to pregnancy.
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