(250) Optimal Interpregnancy Interval after Periviable Birth

ACOG and SMFM recommend advising patients to avoid interpregnancy intervals of less than six months and to counsel regarding the risk and benefits of interpregnancy intervals of less than 18 months. The WHO specifies that after live births an interpregnancy interval of at least 24 months is recommended while after miscarriage an interpregnancy interval of at least 6 months is recommended. However, no guidelines specifically target patients who deliver periviable neonates, many of which do not survive. Our objective was to evaluate the impact of the interpregnancy interval on birth outcomes in women with a prior periviable birth.  




Study Design:

We performed a retrospective cohort study of women with a history of periviable birth (22w0d to 24w6d) from 2001-2020 with a subsequent singleton pregnancy with available outcome data. The primary outcome was gestational age at delivery while secondary outcomes included percent of miscarriage and mode of delivery. Categorical data was evaluated with Chi-square analysis and continuous data was analyzed with Kruskal-Wallis tests.  




Results:

148 patients were included; 34 with an interpregnancy interval of < 6 months, 35 with an interpregnancy interval of 6-18 months and 79 with an interpregnancy interval of >18 months. Most patients were black, multiparous and delivered their index pregnancy due to preterm labor, preterm premature rupture or membranes or cervical insufficiency. Demographics were similar between groups. There were no significant differences in the primary outcome with the median gestational age at delivery for each groups at 37.1 weeks (p=0.898). In addition, the risk of miscarriage (20.6%, 25.7% and 27.7%, p=0.776) and mode of delivery (57.7%, 62.5% and 48.2%, p=0.453) were similar between groups.  




Conclusion:

Our study does not indicate a higher risk of preterm birth or miscarriage in patients with short interpregnancy intervals after periviable birth.