Grand Rounds

Vanishing Twin Following IVF and Risks for Adverse Pregnancy Outcomes

BACKGROUND AND PURPOSE:

Romanski et al. (Obstet Gynecol 2018) assessed the impact of a vanishing twin, following IVF, on perinatal and peripartum outcomes

Retrospective cohort study
- Vanishing twin following IVF
- Fresh or cryopreserved
- Day 3 to 5 transfer
Patients with dichorionic-diamniotic twins were divided in to 3 groups
- Singleton
- Twins
- Vanishing twin
Live birth defined as ≥24 wks
Vanishing twin defined as
- 2 gestational sacs on ultrasound with demise of one twin ≤14 wks or
- No yolk sac or embryonic pole seen in one of the gestational sacs
Primary outcomes
- Gestational age
- Birth weight at delivery
Secondary outcomes were peripartum morbidities
Subanalysis performed based on whether vanishing twin demise was identified before or after fetal cardiac activity was noted

1,189 pregnancies were included in the study
- 798 singleton
- 291 twins
- 100 vanishing twin
Rate of vanishing twin was 25.6% of all twin pregnancies
Mean gestational age at birth and birth weights were
- Singleton: 38.6±2.3 wks and 3,207±644 g
- Twins: 35.5±2.7 wks and 2,539±610 g
- Vanishing twin: 38.5±1.8 wks and 3,175±599 g
Vanishing twin pregnancies, compared to twin pregnancies had lower odds of
- Preterm delivery: adjusted odds ratio (aOR) 0.12, 95% CI 0.07-0.22
- Small-for-gestational-age birth weight: aOR 0.14, 95% CI 0.07-0.28

For IVF pregnancies, vanishing twin outcomes for preterm birth and weight at birth were similar to those of singleton pregnancies
Both vanishing twin and singleton had better outcomes than twin pregnancies

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