Improved IVF outcomes with interpregnancy interval of at least six months

For women undergoing in vitro fertilization (IVF), delaying the next frozen embryo transfer (FET) for at least six months after a clinical pregnancy loss (CPL) is associated with improved pregnancy outcomes, according to a study published online Oct. 31 in JAMA Network Open.

Ze Wang, M.D., from Shandong University in Jinan, China, and colleagues examined the association between different interpregnancy interval (IPI) lengths after a preceding CPL and pregnancy outcomes of the next FET in a retrospective cohort study involving women who underwent frozen-thawed blastocyst transfer within one year after a CPL during IVF treatment. The analysis included 2,433 women who received IVF treatment: 13.9, 55.4, and 30.7 percent with a IPI of less than three months, three to less than six months, and six to 12 months, respectively.

The researchers found that shorter IPIs (less than three and three to less than six months) were associated with reduced odds of clinical pregnancy (adjusted odds ratios, 0.70 and 0.79, respectively), live birth (adjusted odds ratios, 0.64 and 0.74, respectively), and healthy live birth (adjusted odds ratios, 0.63 and 0.79, respectively) compared with an IPI of six to 12 months. Women with shorter IPIs had a higher risk of total pregnancy loss (adjusted odds ratios, 1.87 and 1.29, respectively) compared to women with an IPI of six to 12 months.

"The causal mechanisms that underlie the association between a short IPI and unfavorable pregnancy outcomes remain unclear," the authors write.

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