The Effects of Pregnancy Spacing After a Miscarriage on Subsequent Pregnancy Outcomes: Evidence from Matlab, Bangladesh

Objective To determine the optimum interpregnancy interval following a miscarriage and to see if findings for a poor, rural area in Bangladesh are similar to those in a recent study of Scottish women. Design Multivariate analysis of population-based, prospective data from a demographic surveillance system (study cohort). Setting Pregnancies in Matlab, Bangladesh, between1977 and 2008. Participants 9,214 women with 10,453 pregnancies that ended in a miscarriage and were followed by another pregnancy outcome. Main outcome measures Outcome of pregnancy following the miscarriage was singleton live birth, stillbirth, miscarriage, or induced abortion. For pregnancies that ended in live birth, whether the child died in first week of life, in the next three weeks, or between 29 days and one year of age. Results Compared with interpregnancy intervals (IPIs) of 6-12 months, pregnancies that were conceived less than three months after a miscarriage were more likely to result in a live birth and less likely to result in a miscarriage (adjusted odds ratio 0.70, 95% confidence interval 0.57 to 0.86) or induced abortion (0.50, 0.29 to 0.89). Induced abortions were significantly more likely following IPIs of 18-24 months (2.36, 1.48 to 3.76), 36-48 months (2.73, 1.50 to 4.94), and more than 48 months (3.32, 1.68 to 2.95), and miscarriages were more likely following IPIs of 12-17 months (1.25, 1.01 to 1.56) and more than 48 months (1.90, 1.40 to 2.58). No significant effects of IPI duration are seen on the risks of a stillbirth. These results are remarkably similar to those Love et al. found for Scottish women. However, we find a different pattern when we consider whether the infant born at the end of the IPI died: Compared to IPIs of 6-12 months, the shortest IPIs following a miscarriage (≤3 months) are associated with significantly higher late neonatal mortality (adjusted relative risk ratio 1.74, 1.06 to 2.84), and IPIs of 12-18 months are associated with a significantly lower unadjusted risk of post-neonatal mortality (0.54, 0.30 to 0.96). Conclusions The shorter the IPI following a miscarriage, the more likely the subsequent pregnancy is to result in a live birth. However, very short IPIs may not be advisable in poor countries like Bangladesh because they are associated with a higher risk of mortality for the infants born after them.