The ESPRiT Twin Study

The ESPRiT Study represents the largest prospective cohort of intensively monitored twin pregnancies studied to date. Through intensive prenatal sonographic surveillance and collation of perinatal and neonatal data (with 100% complete follow-up of outcomes now achieved), the ESPRiT investigators aimed to establish a degree of intratwin size discordance, for both monochorionic and dichorionic twin pregnancies, that is independently associated with adverse perinatal outcome. In current clinical practice, a definition of ‘significant' intratwin size discordance has been set at an arbitrary 20%. There is currently no agreement among practitioners in relation to whether this cut-off is appropriate, and indeed what additional fetal surveillance or management issues are merited where intratwin size discordance is identified.

Birthweight Discordance

The ESPRiT investigators also aimed to clarify a level of twin size discordance that merits heightened fetal surveillance and consideration for iatrogenic preterm delivery in such cases. No current practice guidelines (Royal College of Obstetricians and Gynaecologists/ American College of Obstetricians and Gynecologists) have been developed in this high-risk area.

This research has revealed that a difference of 18% or more in twin birth weights is associated with an increased risk of fetal or neonatal death, bowel complications, breathing difficulties, infection and admission to the neonatal intensive care unit. Twins who shared a single placenta, ‘monochorionic' twins, were found to be at the highest risk and the larger twin was at equal risk of morbidity as his/her smaller co-twin. These findings have recently been published in Obstetrics and Gynecology and the American Journal of Obstetrics and Gynecology.

Mode of Delivery

The ESPRiT study also found that 77% of twin labour trials (natural labour, performed under observation by an obstetrician in order to achieve vaginal birth) were successful and infant morbidity rates were no different from those following a planned caesarean twin delivery. In 4% of cases, the mother underwent a normal birth of the first twin, followed by caesarean delivery of the second baby; a rate somewhat lower than that observed internationally.

Notwithstanding the comparatively low morbidity and mortality rates observed in the ESPRiT twin cohort, twins are known to be at increased risk for stillbirth in the third trimester when compared to singleton pregnancies and it is for this reason that many obstetricians internationally are now motivated to deliver such twins preterm. A paper due to be published by the ESPRiT group shortly in Obstetrics and Gynecology sets out to determine the optimal timing of planned delivery for uncomplicated twins. This study has found that the risk of stillbirth among single placenta twins after 34 weeks is 1.5% and that while planned delivery of all such twins may abolish that specific risk, such a decision incurs a cost of neonatal morbidity that translates into rate of admission to Neonatal intensive care of 88% at 34 weeks, falling to 9% at 38 weeks.

Secondary Analysis

Secondary analysis of the ESPRiT Study data is still underway. A range of topics covering the secondary objectives defined in the ESPRiT Study protocol have been identified. Expressions of interest are invited from PIs and associated researchers/ clinicians (from Perinatal Ireland centres and elsewhere) to interrogate the ESPRiT database on these and other topics. A number of papers are in preparation. The process is overseen and managed by Dr Fionnuala Breathnach, Lead Researcher for the ESPRiT Study.

For Further information contact Dr Liz Tully, Programme Manager

ESPRiT Oral Presentations


  • Definition of “significant” intra-twin birth weight discordance: The ESPRIT Study- Fionnuala Breathnach, Society Maternal Fetal Medicine, Feb 2011
  • Placental cord insertion and birthweight discordance in twin pregnancies: results of the national prospective ESPRiT trial. –Etaoin Kent, Society Maternal Fetal Medicine, Feb 2011
  • Can ultrasound at thirty-two weeks gestation predict the presentation of twins at the time of delivery K. O’Donoghue,International Society of Ultrasound in Obstetrics and Gynaecology, Sept 2011
  • Different outcomes between the first and second Twin - Stephen Carroll,International Congress on Twin Studies, April 2012
  • The optimal timing of delivery of monochorionic twins- Rhona Mahony, International Congress on Twin Studies, April 2012
  • National Clinical Practice Guideline on Multiple Pregnancy Management – Fionnuala Breathnach, National Summit on Clinical Guidelines in Obstetrics & Gynaecology, October 2012