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Single intrauterine fetal death in monochorionic twins

Key points

  • Monochorionic (MC) twins constitute 20-30% of all twin pregnancies and 2.6-6.2% will have a single intrauterine fetal death.
  • This event is associated with increased risk of premature delivery and perinatal mortality and morbidity for the other twin.
  • There is a lack of robust data regarding the incidence of single twin demise; interventions offered; maternal, fetal and neonatal outcomes and any prognostic indicators.
  • The knowledge gained from this study will enable recommendations for the management of monochorionic twin pregnancies following single twin demise and improve the counselling and management.

Surveillance Period

1st July 2016 –  30th June 2017


Perinatal mortality is increased in multiple compared to singleton pregnancies, with single twin demise presenting a rare but unique perinatal problem with reported incidence of single twin demise after 14 weeks between 2.6 to 6.2 percent of all twin pregnancies[1].  Fetal morbid sequelae may include prematurity, death of the surviving fetus or survival with perinatal morbidity[2]. In addition, maternal morbidity has been reported as increased with higher (than background) rates of pre-eclampsia, coagulopathy and sepsis[3][4]. Management of pregnancies complicated by intrauterine death in a twin may be challenging as controversy exists regarding the optimal time of delivery, the frequency of antenatal surveillance, the appropriate investigations to determine cerebral damage and neurologic morbidity and the effects on maternal wellbeing (both physical and psychological) of retaining one dead fetus. Current evidence is limited by small numbers and significant heterogeneity in terms of diagnosis, investigation, management and post-natal follow-up.


To use the UK Obstetric Surveillance System (UKOSS) to determine the incidence of single twin demise in MC twin pregnancies and the adverse maternal, fetal and neonatal outcomes.

Research questions

  • What is the incidence of single twin demise in the UK?
  • What are the characteristics of pregnancies affected by single twin demise (maternal demographics, gestation, suspected aetiology)?
  • What is the nature and incidence of antenatal intervention following single twin demise?
  • What are the maternal, fetal and neonatal outcomes following single twin demise?
  • Are there prognostic indicators associated with single twin demise? E.g. maternal age

Case definition

All women in the UK with a monochorionic twin pregnancy with single twin demise after 14 weeks gestation, defined as:

  1. Monochorionic twin pregnancy – chorionicity confirmed at first trimester scan (<14 weeks) due to ultrasonic absence of the lambda sign (an echogenic V-shaped chorionic projection of tissue in dichorionic placentation)
  2. Single intrauterine fetal death – intrauterine death of one twin after 14 weeks of gestation (including spontaneous single twin demise or selective feticide but excluding twin reversed arterial perfusion sequence)

Please include all women who deliver during the study period, irrespective of the presumed date of fetal demise

Exclude: Higher order multiple pregnancies where multi-fetal pregnancy reduction has taken place


This study is being funded by the British Maternal Fetal Medicine Society (BMFMS) and Twins and Multiple Births Association (TAMBA).

Ethics committee approval

This study has been approved by the North London REC1 (REC Ref. Number: 10/H0717/20).

Lead Investigator

Professor Mark Kilby, Dr Katie Morris, University of Birmingham; Professor Marian Knight NPEU.

Sample Data Collection Form (DCF)

UKOSS Single Twin Demise Form


  1. ^ Pharoah PO & Adi Y. Lancet 2000;355:1597-602.
  2. ^ Hillman SC et al. Obstet Gynecol. 2011;118(4):928-40.
  3. ^ Santema JG et al. Br J Obstet Gynaecol 1995;102:26-30.
  4. ^ Kilby MD et al. Obstet Gynecol. 1994;84(1):107-110.

Updated: Friday, 09 October 2020 10:27 (v11)

Contact us

For more information about UKOSS, please view the contact details page