Health outcomes for Massachusetts infants after fresh versus frozen embryo transfer.

Objective: To compare neonatal health outcomes after fresh versus frozen ET (FET).

Design: Retrospective analysis of a population-based database of linked clinically assisted reproductive technology (ART) data with state vital records. Multivariable logistic regression was used to model the association between deliveries from fresh versus FET and adverse health outcomes, controlling for maternal characteristics.

Setting: Not applicable.

Patient(s): Live-born singleton infants born to Massachusetts women who conceived by fresh or FET after ART using autologous oocytes between July 1, 2004, and December 31, 2013.

Intervention(s): None.

Main Outcome Measure(s): Preterm birth, low birth weight, neonatal mortality, birth defects, organ system conditions.

Result(s): Compared with infants conceived from fresh embryos, those born to mothers who underwent FET were less likely to be small for gestational age (adjusted odds ratio [AOR] = 0.56; 95% confidence interval [CI], 0.44-0.70) and low birth weight (AOR = 0.72; 95% CI, 0.59-0.88) but more likely to be large for gestational age (AOR = 1.47; 95% CI, 1.26-1.70) and to experience greater odds of infectious disease (AOR = 1.46; 95% CI, 1.03-2.06), respiratory (AOR = 1.23; 95% CI, 1.07-1.41), and neurologic (AOR = 1.32; 95% CI, 1.04-1.68) conditions. There were no statistically significant differences in preterm birth, neonatal mortality, birth defects, cardiovascular, hematologic, and gastrointestinal/feeding conditions, and for infants ≥ 35 weeks, no statistically significant differences in prolonged hospital stay (>3 days for vaginal delivery, >5 days for cesarean).

Conclusion(s): Compared with infants conceived from fresh ET, those born by FET have higher birth weight but increased odds of infectious disease, hematologic, respiratory, and neurologic abnormalities. These risks should be considered when making decisions on fresh versus FET.