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218: Risks of preterm premature rupture of membranes and preterm birth based on location of trocar insertion site

      Objective

      Preterm premature rupture of membranes (PPROM) and preterm birth (PTB) are known risks of invasive fetal interventions such as laser surgery for twin-twin transfusion syndrome (TTTS). The aim of this study was to assess whether the location of the trocar insertion site on the maternal abdomen was associated with PPROM and PTB. We hypothesized that the risks were higher for insertions that enter the uterus in the lower uterine segment (LUS) and in lateral entries.

      Study Design

      Data were aggregated from two centers that perform percutaneous laser surgery for TTTS with identical protocols. Trocar location was prospectively documented in the operating room in centimeters (cm) vertically from the symphysis pubis and horizontally from the midline; LUS location was defined as any insertion <10 cm from the pubic symphysis on the vertical axis, and lateral location was defined as >5 cm from the midline in either direction on the horizontal axis. Patient characteristics, including trocar location (LUS y/n and Lateral y/n), were tested bivariately against 3 outcomes of interest: PPROM < 21 days, PTB < 28 weeks, and PTB < 32 weeks. For each outcome, multiple logistic models were fitted to examine the effect of trocar location, controlling for other potential risk factors. Odds ratios (OR) are reported with 95% confidence intervals.

      Results

      751 patients were studied. In bivariate analysis, LUS location was associated with PPROM < 21 days (18.3% vs. 8.8%, p = 0.0355), but not with PTB < 28 weeks (10.7% vs. 9.4%, p=0.72) or PTB < 32 weeks (12.2% vs. 8.2%, p = 0.09). Lateral location was not associated with any of the 3 outcomes. Results were confirmed with logistic regression models. Patients with LUS location were twice as likely as those with a more superior location to have PPROM < 21 days (OR = 2.17, 1.06-4.46), after controlling for placental location, Quintero stage, gestational age at procedure, preoperative vaginal bleeding, and study center.

      Conclusion

      After controlling for potential confounders, we found that trocar insertion in the LUS appeared to be associated with an increased risk of PPROM but not preterm birth. Inherent differences in the local milieu of the fetal membranes may explain these findings. Although the site of trocar insertion is often restricted by case-specific factors, it is reasonable to avoid the lower uterine segment if technically feasible.