First trimester pregnancy loss after fresh and frozen in vitro fertilization cycles

To characterize risks for early pregnancy loss after fresh and frozen IVF cycles and to investigate whether risk is modified by infertility diagnoses or transfer of embryos in fresh versus frozen cycles.

Retrospective cohort study using data from the National Assisted Reproductive Technology (ART) Surveillance System.

Fertility centers.

Clinical pregnancies achieved with fresh and frozen IVF cycles between 2007 and 2012 (N = 249,630).

None.

First trimester pregnancy loss.

A diagnosis of uterine factor was associated with an increased risk of loss in women aged 40 years and younger (<30 years: adjusted risk ratio (aRR) = 1.24, 95% confidence interval (CI) 1.04-1.48; 30-34 years: aRR = 1.27, 95% CI 1.17-1.38; 35-37 years: aRR = 1.12, 95% CI 1.03-1.21; 38-40 years: aRR = 1.08, 95% CI 1.01-1.17). There was an increased risk of loss in women with diminished ovarian reserve aged 30-34 years (aRR = 1.08, 95% CI 1.01-1.15) and in women with ovulatory dysfunction younger than 35 years (<30 years: aRR = 1.12, 95% CI 1.05-1.19; 30-34 years: aRR = 1.07, 95% CI 1.02-1.13). There was an increased risk of loss after frozen ETs versus fresh among women younger than 38 years, but this remained significant in the subanalysis of similar quality embryos only in women younger than 30 years (aRR = 1.16, 95% CI 1.04-1.32).

Uterine factor had the largest increased risk of loss among infertility diagnoses, although the magnitudes of all risks were small. When transferring embryos of similar quality, the risks of loss were similar between fresh and frozen cycles.