Obstetric and Neonatal Outcomes of Twin Pregnancies Following Double Embryo Transfer on Day 3 versus Day 5

Background: Multiple pregnancies following assisted reproductive technologies (ART) remain a major contributor to perinatal morbidity and mortality. While the impact of embryo transfer day —cleavage-stage (day 3) versus blastocyststage (day 5)— has been extensively studied in singleton pregnancies, data focusing specifically on twin pregnancies resulting from double embryo transfer (DET) are limited. This study aimed to compare obstetric and neonatal outcomes of twin pregnancies following DET on day 3 (D3) versus day 5 (D5).Methods: This retrospective single-centre cohort study included fresh ART cycles performed between 2010-2022. A total of 47 liveborn twin pregnancies following DET were analysed (D3: n = 28; D5: n = 19). Maternal demographic and clinical characteristics were recorded. Primary outcomes included gestational age at birth, birthweight, and composite adverse perinatal outcome (CAPO). Secondary outcomes included neonatal morbidities such as NICU admission, respiratory distress syndrome, sepsis, and neonatal mortality.Results: Maternal baseline characteristics were comparable between groups. Gestational age at birth and birthweight did not differ significantly between D3 and D5 transfers (p >0.05). The incidence of CAPO was similar in both groups (35.7% vs 39.5%, p=0.711). Rates of NICU admission, Apgar score ≤ 7 at 5 minutes, respiratory distress syndrome, and neonatal mortality were also comparable.Conclusions: The day of double embryo transfer (D3 vs D5) was not associated with obstetric or neonatal outcomes in twin pregnancies. These findings suggest that limiting embryo number and appropriate patient selection are more critical than transfer day in reducing risks related to multiple pregnancies.