Interpregnancy Interval and Singleton Live Birth Outcomes From In Vitro Fertilization

Area of Science:

• Reproductive Medicine
• Perinatal Epidemiology
• Assisted Reproductive Technology

Background:

• Short interpregnancy intervals (IPIs) are linked to adverse outcomes in spontaneous conceptions.
• The impact of IPIs on pregnancies conceived via assisted reproductive technology (ART) requires specific investigation.

Purpose of the Study:

• To determine the association between short interpregnancy intervals and adverse pregnancy outcomes in women undergoing ART.
• To provide evidence-based recommendations for optimal timing of subsequent ART cycles after a live birth.

Main Methods:

• Retrospective analysis of ART Clinic Outcome Reporting System data (2004-2013).
• Inclusion of patients with a history of live birth from autologous in vitro fertilization (IVF).
• Logistic regression models assessed preterm delivery and low birth weight in relation to IPI, adjusting for covariates.

Main Results:

• An interpregnancy interval (IPI) less than 12 months was observed in 40.9% of cycles.
• Compared to an IPI of 12 to <18 months, intervals <6 months increased preterm delivery odds by 1.66 (95% CI 1.05-2.65).
• An IPI of 6 to <12 months was linked to a 3.0% increase in preterm delivery and a 2.7% increase in low birth weight.

Conclusions:

• An interpregnancy interval of less than 12 months following a live birth via ART is associated with higher rates of preterm delivery and low birth weight.
• Delaying subsequent in vitro fertilization (IVF) treatment for at least 12 months post-delivery is supported by these findings.
• Unlike natural conception, extended intervals beyond 12 months do not appear to offer additional benefits for ART-conceived singleton births.