BACKGROUND AND PURPOSE: 

• Monochorionic Monoamniotic (mono/mono) twinning is associated with significant risk for perinatal mortality, usually due to cord entanglement   
  • Largest study reported perinatal mortality of 20%, with increased risk >32 weeks 
• Data regarding optimal monitoring and timing of delivery are limited 
• Saccone et al. (Ultrasound in Obstetrics and Gynecology, 2018) compared perinatal outcomes of non-anomalous monoamniotic twins based on whether surveillance was provided in an inpatient vs outpatient setting

METHODS: 

• Multinational, retrospective, cohort study 
  • Clinical records of all consecutive women with mono/mono twin pregnancies
  • 10 centers managed inpatients | 12 centers managed outpatients 
• Outpatient care 
  • Q3weeks: EFW and deepest vertical pocket  
  • Q2weeks: umbilical artery Doppler and middle cerebral artery peak systolic velocity 
  • Q1week: Standard NST or CTG  
• Inpatient 
  • Admission: 26w0d-27w6d until delivery 
  • NST 2 to 3x day 
  • Q3weeks: EFW and deepest vertical pocket  
  • Q2weeks: umbilical artery Doppler and middle cerebral artery peak systolic velocity 
• Delivery Timing  
  • Planned cesarean delivery usually at 32w0d-34w6d
• Primary outcome 
  • Intrauterine fetal death 
  • Maternal length of stay   
• Secondary outcomes 
  • Fetal death rate
  • Neonatal death rate

RESULTS: 

• 194 consecutive pregnant women with non-anomalous uncomplicated monoamniotic twin gestations (390 fetuses) were included  
  • 38.5% inpatients | 61.5% outpatients 
  • The overall perinatal loss rate was 10.8% (42/390)  
  • Peak fetal death rate (4.3%) at 29 weeks  
• No significant difference between groups in 
  • Mean gestation age at delivery: 31 weeks 
  • Mean Birth weight: Approximately 1.6 kg  
  • Emergency delivery rate  
• Using standard logistic regression analysis, inpatient management compared to outpatient resulted in significantly
  • Lower rate of IFUD: 3.3% vs 10.8%; OR 0.28 (95% CI, 0.11 to 0.76)
  • Lower rate of Perinatal death: 4.0% vs 15.0%; OR 0.24 (95% CI, 0.10 to 0.58)
  • Shorter length of NICU stay: Mean difference -15.90 days (95% CI -23.55 to -8.25)
• Using ‘mixed model’ analysis
  • When comparing inpatient to outpatient surveillance, there was no statistically significant difference in fetal death rates (monitoring starting 26 weeks inpatient vs 30 weeks outpatient)
  • Adjusted OR 0.21 (95% CI 0.04 to 1.17) (P=0.07) 
• Maternal length of stay  
  • Inpatient: 42.1 days
  • Outpatient 7.4 days  
  • Mean difference: 34.70 days (95% CI, 31.31 to 38.09) 

CONCLUSION: 

• In uncomplicated monoamniotic twins, inpatient and outpatient surveillance were comparable when using a ‘mixed model’ analysis to account
  • Standard logistic analysis considers each twin individually and did demonstrate benefit with inpatient surveillance
  • ‘Mixed model’ analysis takes in to account that the second twin has an increased risk of fetal death after the first twin dies
• The main difference in fetal mortality outcomes was observed from 26-30 weeks 
  • Once monitoring begins, outcomes are similar  
• Mixed model approach takes in to account that the 2nd twin has an increased risk of death based on the loss of the first twin  
• After 31 6/7 there were no intrauterine fetal deaths or neonatal deaths 
• Improved survival rates in this study may reflect the exclusion of fetal anomalies and therefore this study may be more reflective of ‘uncomplicated’ cases of mono/mono twins  
• This study supports the findings of the original MONOMONO trial that delivery can be planned from 32w0d to 34w6d of gestation 
  • Present study underpowered to recommend beyond 34 completed weeks   
• The authors state that 

once monitoring is instituted (be it in the inpatient or in the outpatient group) survival of monoamniotic twins is excellent, and outcomes of inpatient and outpatient groups are similar.

Learn More – Primary Sources: 

Prenatal management and timing of delivery of uncomplicated monochorionic monoamniotic twin pregnancy: the MONOMONO study

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