Vanishing Twin Syndrome is Associated With Adverse Perinatal Outcomes in Fresh In Vitro Fertilization Cycles [23G]

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To investigate whether the presence of a vanishing sac (VS) is associated with adverse perinatal outcomes in women undergoing fresh in vitro fertilization (IVF)—embryo transfer (ET) cycles.


Retrospective cohort study of women with live singleton births with and without a VS after fresh IVF-ET between January 2004 and June 2013. Baseline demographics and ovarian stimulation response between the two groups were compared. Additional characteristics compared included incidence of preterm birth (PTB), birth weight, low birth weight (LBW), very low birth weight (VLBW), and term LBW. Odds ratios (OR) with 95% confidence intervals (CI) were calculated and adjusted with multivariate logistic regression analysis when indicated.


4049 patients with live singleton births met inclusion criteria—853 and 3196 with and without a VS, respectively. There was no difference in the baseline demographics or ovarian stimulation response between the groups. The VS group had a lower overall birth weight compared to the group without a VS (3279.5±369.9 grams vs 3368.6±567.5 grams; P<.01). The findings of a VS was also associated with an increased odds of overall LBW (OR 1.75, 95% CI 1.36–2.25; P<.01) and an increased odds of term LBW (OR 3.44, 95% CI 2.14–5.53; P<.01). VS was not associated with a higher incidence of PTB or overall VLBW.


Our findings suggest that a VS is associated with lower overall birth weight and higher odds of overall LBW and term LBW in live singleton births after fresh IVF-ET cycles.

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