Quinn MM, et al. - The relationship between a short interpregnancy interval and adverse pregnancy outcomes were described in the population undergoing assisted reproductive technology. This nationally representative population suggested increased rates of preterm delivery and low birth weight in singleton live births from assisted reproductive technology in association with an interval from delivery to treatment start of less than 12 months, thereby supporting a delay in the start of in vitro fertilization (IVF) treatment by 12 months from a live birth. However, a benefit from a longer interval, as has been recommended for naturally conceiving couples, is not suggested.

Methods

• Using data from the Society for Assisted Reproductive Technology Clinic Outcome Reporting System, researchers performed a retrospective analysis.
• Patients with a history of live birth from assisted reproductive technology who returned for a fresh, autologous IVF cycle from 2004 to 2013 were included.
• The interval from live birth to cycle start was defined as interpregnancy interval.
• With adjustment for age, body mass index, and history of preterm delivery, logistic regression models of preterm delivery (less than 37 weeks of gestation) and low birth weight (less than 2,500 g) on interpregnancy interval were fit.
• From the logistic model, researchers generated predicted probabilities.

Results

• Researchers identified 51,997 fresh IVF cycles after an index live birth; of these, 17,536 resulted in a repeat live birth with 11,271 singleton live births from autologous IVF.
• In 40.9% of cycles, an interpregnancy interval of less than 18 months was noted.
• They identified that compared with a reference interpregnancy interval of 12 to less than 18 months, the adjusted odds ratio for singleton preterm delivery was 1.66 (95% CI 1.05–2.65) for an interpregnancy interval less than 6 months and 1.34 (95% CI 1.06–1.69) for 6 to less than 12 months.
• A 3.0% increase in preterm delivery (13.6±1.1% vs 10.6±0.7%, P=.030) and a 2.7% increase in low birth weight (8.0±0.9% vs 5.3±0.5%, P=.025) were observed in association with an interpregnancy interval 6 to less than 12 months vs an interpregnancy interval of 12 to less than 18 months.