Recurrence risk and risk factors for monozygotic twin and triplet birth in over 65,000 single-embryo transfers.

PURPOSE: To determine the recurrence risk and risk factors for monozygotic splitting after elective single-embryo transfers (eSET). METHODS: A retrospective cohort study was performed investigating 65,664 eSET cycles that resulted in a clinical pregnancy as reported in the Society for Assisted Reproductive Technology (SART) Clinical Outcomes Reporting System (CORS) between 2004 and 2017. Monozygosity was defined as more than one fetal heart tone by the first-trimester ultrasound and concordant sex at live birth. The primary outcome was recurrence risk, with recurrence defined as one patient having two or more cycles of eSET resulting in monozygotic multiples. The secondary objective was to identify factors associated with smonozygotic splitting, using a multivariable logistic regression model and a stepwise purposeful model selection. RESULTS: There were 1355 (2.05%) pregnancies that resulted in two or more fetal heart tones after SET, including 840 monozygotic twins and triplets at birth. Recurrence occurred in two cases-0.0001% of patients with multiple eSET cycles. One case resulted from embryos created from a single cohort with intracytoplasmic sperm injection (ICSI), assisted hatching (AH), and blastocyst transfers. The second case resulted from donor egg embryos with ICSI and blastocyst transfers. Risk factors associated with monozygotic live birth were blastocyst transfer (OR 1.23, 95% CI 1.04-1.47, P = 0.0176) and AH (OR 1.23, 95% CI 1.05-1.44, P = 0.0081). CONCLUSION: Recurrence of monozygotic live births in eSET was very rare. Blastocyst transfer and AH were confirmed to be risk factors for monozygotic live births, while ICSI, PGT, and FET do not appear to be associated.

Electronic Fetal Monitoring and Neonatal Outcomes when a Nuchal Cord Is Present at Delivery.

OBJECTIVE: This study aimed to determine the association between nuchal cord, electronic fetal monitoring parameters, and adverse neonatal outcomes. STUDY DESIGN: This was a prospective cohort study of 8,580 singleton pregnancies. Electronic fetal monitoring was interpreted, and patients with a nuchal cord at delivery were compared with those without. The primary outcome was a composite neonatal morbidity index. Logistic regression was used to adjust for confounders. RESULT: Of 8,580 patients, 2,071 (24.14%) had a nuchal cord. There was no difference in the risk of neonatal composite morbidity in patients with or without a nuchal cord (8.69 vs. 8.86%; p = 0.81). Nuchal cord was associated with category II fetal heart tracing and operative vaginal delivery (OVD) (6.4 vs. 4.3%; p < 0.01). CONCLUSION: Nuchal cord is associated with category II electronic fetal monitoring parameters, which may drive increased rates of OVD. However, there is no significant association with neonatal morbidity.

True knot at the time of delivery: electronic fetal monitoring characteristics and neonatal outcomes.

OBJECTIVE: Determine the association between electronic fetal monitoring and neonatal outcomes in the setting of a true knot at delivery. STUDY DESIGN: This was a planned secondary analysis of a prospective cohort of 8580 women. Patients with and without a true knot were compared and the primary outcome was repetitive late decelerations occurring with at least 50% of contractions. Confounders were adjusted for using logistic regression. RESULTS: A total of 8580 patients met inclusion criteria and 49 (0.57%) had a TK. There was no significant difference in the rate of repetitive late decelerations in patients with TK (aOR 1.04; 95% confidence interval [CI] 0.25-4.40),other electronic fetal monitoring parameters, or neonatal outcomes. CONCLUSION: Neonates with true knots who are delivered at term have similar electronic fetal monitoring characteristics compared to those without true knots and no detectable difference in neonatal morbidity; thus, calling into question the clinical significance of a true knot at term.