Objective: To assess whether interpregnancy interval length after a pregnancy loss is associated with risk of repeat miscarriage.
Methods: This analysis includes pregnant women participating in the Right From the Start (2000-2012) community-based prospective cohort study whose most recent pregnancy before enrollment ended in miscarriage. Interpregnancy interval was defined as the time between a prior miscarriage and the last menstrual period of the study pregnancy. Miscarriage was defined as pregnancy loss before 20 weeks of gestation. Cox proportional hazard models were used to estimate crude and adjusted hazard ratios and 95% CIs for the association between different interpregnancy interval lengths and miscarriage in the study pregnancy. Adjusted models included maternal age, race, parity, body mass index, and education.
Results: Among the 514 study participants who reported miscarriage as their most recent pregnancy outcome, 15.7% had a repeat miscarriage in the study pregnancy (n=81). Median maternal age was 30 years (interquartile range 27-34) and 55.6% of participants had at least one previous livebirth (n=286). When compared with women with interpregnancy intervals of 6-18 months (n=136), women with intervals of less than 3 months (n=124) had the lowest risk of repeat miscarriage (7.3% compared with 22.1%; adjusted hazard ratio 0.33, 95% CI 0.16-0.71). Neither maternal race nor parity modified the association. Attempting to conceive immediately was not associated with increased risk of miscarriage in the next pregnancy.
Conclusion: An interpregnancy interval after pregnancy loss of less than 3 months is associated with the lowest risk of subsequent miscarriage. This implies counseling women to delay conception to reduce risk of miscarriage may not be warranted.