Monochorionic diamniotic in vitro fertilization twins have a decreased incidence of twin-to-twin transfusion syndrome.

Objective: To compare the incidence of twin-to-twin transfusion syndrome (TTTS) in spontaneous versus IVF-conceived twin pregnancies.

Design: Retrospective multicenter study.

Setting: University-affiliated tertiary medical centers.

Patient(s): Women admitted for 11-14 week's scan between January 1997 and July 2013 who were diagnosed with monochorionic (MC) diamniotic twin pregnancies.

Intervention(s): None.

Main Outcome Measure(s): Mode of conception, TTTS.

Result(s): The study cohort included 327 pregnant women with live MC diamniotic twins. Of them, 284 (86.9%) and 43 (13.1%) were spontaneous and IVF conceived, respectively. The mean maternal age was significantly higher in IVF compared with in spontaneously conceived pregnancies (33.8 ± 5.5 vs. 31.6 ± 5.4, respectively). Thirty-seven twins (11.3%) had TTTS, of whom 36/284 (12.7%) versus 1/43 (2.3%) were spontaneously and IVF conceived, respectively. The mean week of delivery was significantly lower in MC twins diagnosed with TTTS compared with those without TTTS (32.7 ± 3.3 vs. 35.5 ± 2.5, respectively). Furthermore, there was a significantly higher birthweight discordancy in twins diagnosed with TTTS compared with those without (20.6% vs. 11%, respectively).

Conclusion(s): The significantly lower proportion of TTTS found in IVF-conceived twins may suggest a different embryological process that lies at the core of IVF conception of monozygotic twinning.