BACKGROUND AND PURPOSE: 

• Vanishing twin is a relatively common occurrence in pregnancies conceived with IVF, while natural occurrence is less well known  
• Márton et al. (Fertil Steril 2016) evaluated whether there is a difference between vanishing twin pregnancy outcome following IVF-ICSI compared to natural conception  

METHODS: 

• Longitudinal, retrospective cohort study (1994-2014) 
• Vanishing twin cases were matched to singleton controls 
• Monochorionic twins were excluded  
• Vanishing twin diagnosis <14 weeks 
  • Two viable embryos with cardiac activity with spontaneous reduction of one embryo or  
  • Single viable embryo and an additional gestational sac established  
• Primary outcome was obstetric and neonatal outcome data 
• Data adjusted for  
  • Maternal Age | Parity | Chronic maternal diseases | Obstetric history data  

RESULTS: 

• 65,237 singleton deliveries were identified 
  • 1,563 twins, of which 306 vanishing twins 
  • Vanishing twin rate: 4.69/1000  
  • There were 78 IVF-ICSI vanishing twin cases and 228 natural conception vanishing twin cases   
• The incidence of a embryonic/fetal loss <14 weeks was higher after natural conception (18.2%) than after IVF-ICSI (12.6%); P=0.002
• 5.2% of singleton deliveries that originated from a pregnancy where vanishing twin was noted followed ART vs 0.37% after a spontaneous pregnancy
• In IVF-ICSI vanishing twin pregnancies, when compared to matched controls  
  • Gestational diabetes risk was increased; adjusted odds ratio (aOR) 0.80 (natural) vs 3.10 (IVF-ICSI) 
  • Pregestational diabetes risk was increased: aOR 1.00 (natural) vs 1.07 (IVF-ICSI) 
  • Retained placenta: aOR 0.67 (natural) vs 7.2 (IVF-ICSI) 
• IUGR risk increased in both IVF-ICSI and spontaneous vanishing twin 
  • IVF–ICSI: aOR 9.2; 95% CI, 5-22  
  • Spontaneous conception: aOR 3.0; 95% CI, 1.8-5.2 
• Risk for vanishing twin in a spontaneous conception was increased with  
  • Previous induced abortion: aOR 1.34 
  • Second-trimester fetal loss: aOR 3.3 
• Risk factors for vanishing twin following IVF-ICSI  
  • Gestational diabetes mellitus in previous pregnancy: aOR 5.41 
  • Gestational diabetes in current pregnancy: aOR 2.3  
  • Chronic maternal diseases: aOR 3.5 
• No associations found with preeclampsia or preterm birth

CONCLUSION: 

• Vanishing twin pregnancies had a lower prevalence but worse perinatal outcome after IVF-ICSI, compared to natural conception 
  • Lower occurrence of a vanishing twin in ART pregnancies is likely due to selection against abnormal embryos during the IVF-ICSI procedure
• Vanishing twin appears to be an independent risk factor for adverse perinatal outcomes  
  • Vanishing twin may “induce growth restriction in the remaining twin”  
• Risk factors for vanishing twin suggests that adverse outcomes may correlate with maternal/infertility background rather than the ART procedure

Learn More – Primary Sources:  

Prevalences and pregnancy outcome of vanishing twin pregnancies achieved by in vitro fertilization versus natural conception

Related ObG Topics:

ASRM guidance: ART and recommended number of embryos to transfer

Are Offspring of IVF/ICSI Pregnancies at Higher Risk for Congenital Heart Defects?

Does ART Increase Risk of Postpartum Hemorrhage?

Infertility Treatment and Childhood Development