PURPOSE: To study the effects of frozen embryo transfer (FET) and FET post-PGT on pre-term and very pre-term births in patients undergoing in vitro fertilization (IVF).

MATERIALS AND METHODS: A study was conducted using the SART National Summary Report from 2014 to 2017. Cycle inclusion criteria were eSET, fresh embryo transfers (ET), frozen embryo transfers without PGT (FET), and frozen embryo transfers with PGT (FET/PGT). Exclusion criteria were use of gestational carriers and donor eggs. Pregnancy outcomes included live births and gestational age at birth.

RESULTS: A total of 161,550 eSETs were analyzed for the effect of FET and FET/PGT on IVF outcome and pre-term births including 43,618 ET, 58,812 FET, and 59,120 FET/PGT cycles. Live birth rates in patients with FET/PGT were significantly higher than those in ET (52.9% vs 46.4%, P < 0.0001) and FET (52.9% vs 43.1%, P < 0.0001). Patients with FET had a significantly lower live birth rate compared with that of ET (43.1% vs 46.4%, P < 0.0001). Both FET and FET/PGT significantly decreased total pre-term births compared with ET (10.8% and 10.5% vs 11.5%, P < 0.05 and < 0.001). FET/PGT significantly reduced very pre-term births when compared with ET and FET (1.5% vs 2.0%, P < 0.0001 and 1.5% vs 1.9%, P = 0.0002).

CONCLUSION: This study demonstrates that PGT significantly improves IVF outcome. Moreover, patients undergoing FET/PGT had significantly decreased total pre-term births. More importantly, patients with FET/PGT had significantly lower very pre-term births.