Associated perinatal determinants of vanishing twin pregnancies achieved by in vitro fertilization vs. spontaneous conception

Purpose To evaluate whether vanishing twin (VT) pregnancies following spontaneous conception have a more adverse perinatal outcome than those conceived after assisted reproduction techniques. Methods The retrospective cohort study consisted of 316 VT pregnancies derived from a hospital database between January 1994 and January 2016 (81 after IVF/ICSI and 235 after spontaneous conception). Results VT was significantly more prevalent after spontaneous conception (in 22.0% of twins) than after IVF/ICSI (in 14.5% of twins). VT pregnancies were significantly more associated with pre-gestational and gestational diabetes mellitus (GDM) in IVF/ICSI pregnancies compared to those spontaneously conceived [adjusted odds ratio (AOR): 4.12 and 11.1, respectively]. IVF-related placental insertion abnormalities were significantly higher in VT pregnancies. A high risk for VT was recorded in the spontaneous group for those who had previously undergone an induced abortion (AOR 0.56) or second-trimester fetal loss (AOR 0.67). The VT phenomenon was a major prognosticator of intrauterine growth retardation (IUGR) for the remaining fetus in IVF pregnancies (AOR 5.12). After controlling for covariates conjointly, advanced age (AOR 1.3), GDM (AOR 2.1), hypertensive disorders (AOR 3.5), primiparity (AOR 3.8), and placentation anomalies all represented independent risk factors for VT in IVF pregnancies. Conclusions IVF/ICSI poses a higher risk for an adverse perinatal outcome following VT pregnancies as compared with those spontaneously conceived.