Time from oocyte retrieval to frozen embryo transfer in the natural cycle does not impact reproductive or neonatal outcomes

To determine if the time from oocyte retrieval to frozen embryo transfer (FET) in the natural cycle affects reproductive or neonatal outcomes. Retrospective cohort. Not applicable. Five hundred and seventy-six consecutive freeze-all cycles from January 2011 to December 2018 followed by natural cycle FET of a single blastocyst. None. Primary outcome of live birth; secondary outcomes of preterm delivery (24–37 weeks) and small for gestational age (SGA) with a multivariable logistic regression performed with adjustment for age, infertility diagnosis, ovulatory trigger type, and preimplantation genetic testing (PGT). Before adjustment for confounding, we found a statistically significantly different live-birth rate (57.7% vs. 48.6%) for natural cycle FET occurring in the first versus second menstrual cycle, respectively. In a multivariate analysis, performing a natural cycle FET of a single blastocyst in the second compared with the first menstrual cycle did not statistically significantly impact the odds of live-birth rate. After adjustment for age, diagnosis, and ovulatory trigger type, only PGT was associated with statistically significantly increased odds of live birth compared with no PGT. There were no differences in the incidence of SGA (male, 6.6% vs. 2.3%; female, 9.8% vs. 11.1%) or preterm delivery (1.6% vs. 5.6%) between both groups. Performing a natural cycle FET of a single blastocyst in the second compared with the first menstrual cycle after ovarian stimulation did not statistically significantly impact the odds of live birth or neonatal outcomes. El intervalo de tiempo entre la extracción de los ovocitos y el momento de la transferencia de embriones congelados en un ciclo natural no tiene ningún impacto en los resultados reproductivos o perinatales. determinar si el tiempo desde la extracción de los ovocitos hasta la transferencia de los embriones congelados (FET) en un ciclo natural afecta a los resultados reproductivos o perinatales. cohorte retrospectiva. no aplica. 567 ciclos consecutivos de congelación electiva de embriones seguidos de transferencia de embrión único en estadio de blastocisto en ciclo natural entre enero de 2011 y diciembre de 2018. ninguna. resultado primario de recién nacido, resultados secundarios de parto pretérmino (24-37 semanas) y pequeño para la edad gestacional (SGA) con un modelo de regresión logística ajustado para múltiples variables: edad, diagnóstico de infertilidad, tipo de inducción de ovulación y uso de est