Short and Long Interpregnancy Intervals Linked to Higher Risk of Spontaneous Abortion: JAMA

The interval between pregnancies is a potentially modifiable factor that has been linked to various adverse perinatal outcomes. However, the specific impact of IPI on the risk of spontaneous abortion has not been well understood. This study aimed to fill that gap by analyzing data from a large cohort of women who participated in the Chinese National Free Prepregnancy Checkups Project over a decade.

This prospective cohort study included 180,921 women aged 20 to 49 years who had a single healthy live birth and were planning another pregnancy. The study period spanned from January 1, 2010, to December 31, 2020, with statistical analysis conducted from June 20 to October 5, 2023. The primary exposure was the interpregnancy interval, defined as the time between the delivery date of the first live birth and the conception of the subsequent pregnancy. IPIs were categorized into five groups: less than 18 months, 18 to 23 months, 24 to 35 months, 36 to 59 months, and 60 months or longer. The main outcome measured was spontaneous abortion (SA).

Among the 180,921 women included in the analysis, 4,380 SA events were recorded, representing 2.4% of the participants. The study revealed a J-shaped association between IPI and the risk of SA:

Short IPIs (<18 months) were associated with a 15% increased risk of SA (OR, 1.15; 95% CI, 1.04-1.27).

Long IPIs (36-59 months) had a 28% increased risk (OR, 1.28; 95% CI, 1.15-1.43).

Very long IPIs (≥60 months) showed a more than two-fold increased risk (OR, 2.13; 95% CI, 1.78-2.56).

The optimal IPI for minimizing the risk of SA was identified as 18 to 23 months. These findings remained consistent even when analyzed by the mode of previous delivery.

The results of this study underscore the significance of optimal birth spacing for reducing the risk of spontaneous abortion. Short intervals may not allow sufficient time for the mother's body to recover, while long intervals might reflect underlying health issues or decreased fertility.

This cohort study indicates that both short and long IPIs after a healthy live birth are linked to an increased risk of spontaneous abortion. These findings provide crucial insights for healthcare providers and policymakers to develop guidelines and interventions aimed at optimizing birth spacing to enhance maternal and neonatal health outcomes.

Reference:

Hu, X., Yang, Y., Wang, L., Zhao, C., Lyu, X., Liu, M., Wu, H., Lei, J., Li, J., Yao, M., Ding, Y., Zhang, H., He, Y., Wang, Y., Peng, Z., Shen, H., Wang, Q., Zhang, Y., Yan, D., … Ma, X. (2024). Interpregnancy interval after healthy live birth and subsequent spontaneous abortion. JAMA Network Open, 7(6), e2417397. https://doi.org/10.1001/jamanetworkopen.2024.17397