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Interpregnancy interval and singleton pregnancy outcomes after frozen embryo transfer
Molly M Quinn1, Mitchell P Rosen2, Isabel Elaine Allen3
1Department of Obstetrics and Gynecology, University of California Los Angeles, Los Angeles, California.
Objective:
To describe the relationship between interpregnancy interval (IPI) and perinatal outcomes in singleton live births after frozen embryo transfer (FET).
Design:
Retrospective analysis of the Society for Assisted Reproductive Technology Clinical Outcome Reporting System cohort including patients with a history of live birth from ART who returned for an FET cycle between 2004 and 2013.
Setting:
Not applicable.
Patient(S):
A total of 19,270 singleton live births from FET subsequent to a live birth.
Intervention(S):
None.
Main Outcome Measure(S):
Odds for preterm delivery (<37, <34, <28 weeks) and low birth weight (<2,500, <1,500 g) adjusted for age, body mass index, and history of prior preterm delivery.
Result(S):
Of 74,456 autologous FET cycles following an index live birth, 24,091 resulted in a repeat live birth, with 19,270 singleton live births. An IPI of <12 months occurred in 19% of cycles. Adjusted odds (aORs) for preterm delivery at <37 weeks were significantly increased for an IPI of <6 months (aOR 2.05, 95% confidence interval [CI] 1.48-2.84), 6 to <12 months (aOR 1.26, 95% CI 1.06-1.49), and 18 to <24 months (aOR 1.23, 95% CI 1.06-1.43) when compared with the reference interval of 12 to <18 months. Additionally, an IPI of <6 months was associated with increased odds for low birth weight (aOR 3.06, 95% CI 2.07-4.52) and very low birth weight (aOR 5.65, 95% CI 2.96-10.84) compared with an IPI of 12 to <18 months.
Conclusion(S):
In this nationally representative population, an interval from delivery to start of an FET cycle of <12 months is associated with increased odds for preterm delivery among singleton live births. Consistent with data for patients undergoing fresh IVF, the data support delaying FET 12 months from a live birth.
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