Table 4.

Preterm Delivery and Low Birthweight in Singleton Live Births Following Fresh vs. Frozen Embryo Transfer in Same Patient at Different Times: Paired Cycle Analysis

N= 1,356	Fresh Embryo Transfer n= 680	Frozen Embryo Transfer n=676	OR (95% CI)	AOR* (95% CI)
Fullterm	81.1% (550/678)	82.2% (555/675)	Reference	Reference
Preterm Delivery (32 - 37 wks)	14.9% (101/678)	15.9% (107/675)	1.03 (0.73 - 1.46) p=0.49	1.86 (0.73 – 4.71) p=0.19
Very Preterm (<32 weeks)	4.0% (27/678)	1.9% (13/675)	2.44 (1.14-5.20) p=0.02	**
Overall LBW (<2500 grams)	11.5% (78/680)	5.6% (38/676)	2.52 (1.59 - 4.00) p<0.001	4.66 (1.18 – 18.38) p = 0.03
Term LBWˆ (≥ 37 weeks, <2500 gms)	2.4% (13/550)	1.1% (6/555)	3.33 (0.92 – 12.11) p=0.07	N/A ¥
Preterm LBWˆ (<37 weeks, <2500 gm)	50.8% (65/128)	26.7% (32/120)	1.86 (0.74 - 4.65) p=0.19	N/A ¥

^*Adjusted for reporting year, patient age, parity, infertility diagnosis, number of embryos transferred, number of prior ART cycles, prior miscarriage, reduction in fetal heart, multiple pregnancy, implantation rate

^**For adjusted analysis, preterm and very preterm delivery combined

^ˆOnly subjects with recorded data for both gestational age and birthweight were included in analysis.

^¥AOR for term LBW not applicable due to it being an extremely rare event.

AOR for preterm LBW not applicable due to insufficient power to adjust for important covariates.