To determine the optimum timing for planned delivery of uncomplicated monochorionic and dichorionic twin pregnancies.
Unselected twin pregnancies were recruited for this prospective cohort study (N=1,028), which was conducted in eight tertiary referral perinatal centers in Ireland. Perinatal mortality and a composite measure of perinatal morbidity (respiratory distress, necrotizing enterocolitis, hypoxic ischemic encephalopathy, periventricular leukomalacia, or sepsis) were compared between uncomplicated twins that underwent planned preterm delivery compared with monochorionic twins that continued in utero beyond 34 weeks of gestation, and dichorionic twins who continued beyond 36 weeks.
Perinatal outcome data were recorded for 100% of the 1,001 twin pairs that completed the study (n=200 monochorionic and n=801 dichorionic). Overall perinatal mortality was 30 per 1,000 in monochorionic twins and 3.8 per 1,000 among dichorionic twins. The prospective risk of in utero death was 1.5% after 34 weeks of gestation for uncomplicated monochorionic pregnancies, with no deaths among dichorionic twins after 33 weeks. The risk of a composite measure of perinatal morbidity for uncomplicated monochorionic twins fell from 41% (13/32 neonates, 3/6 among elective deliveries) at 34 weeks to 5% (4/84) at 37 weeks (P<.001). Among dichorionic twins, the risk of morbidity fell from 4% (2/52) among elective deliveries at 36 weeks to 1% (5/344) in pregnancies continuing to 38 weeks (P=.231).
Applying a strategy of close fetal surveillance, perinatal morbidity can be minimized by allowing uncomplicated monochorionic pregnancies continue to 37 weeks of gestation and dichorionic twins to 38 weeks. Among monochorionic twins, this approach must be balanced against a 1.5% risk of late in utero death.
Uncomplicated twins can continue beyond 37 weeks of gestation with minimal perinatal morbidity, but among monochorionic twins, this approach must be balanced against a 1.5% risk of late stillbirth.
From the Royal College of Surgeons in Ireland, the UCD School of Medicine and Medical Science, University College Dublin, the National Maternity Hospital, the Rotunda Hospital, and Coombe Women and Infants' University Hospital, Dublin, University College Cork, Cork, the Royal Victoria Maternity Hospital, Belfast, the University College Hospital, Galway, the Mid-Western Regional Maternity Hospital, Limerick, and Our Lady of Lourdes Hospital, Drogheda, Ireland.
Supported by a grant from Health Research Board of Ireland (Grant Code IMA/2005/3).
Presented as a poster at the 31st annual meeting of the Society for Maternal-Fetal Medicine, February 7–12, 2011, San Francisco, California.
The Perinatal Ireland Research Consortium thanks the research sonographers and research staff, who provided intensive serial sonographic surveillance to the study participants and collected all perinatal data: Ms. Cecilia Mulcahy, Ms. Fiona Cody, Ms. Hilda O'Keefe, Ms. Phyl Gargan, Ms. Emma Doolin, Ms. Marion Cunningham, Dr. Richard Horgan, Dr. Mary Higgins, Ms. Annette Burke, Ms. Deborah McCartan, Dr. Cassie Staehr, and Ms. Bernadette McPolin.
Corresponding author: Fionnuala Breathnach MD, Royal College of Surgeons in Ireland, Rotunda Hospital, Parnell Square, Dublin 1; e-mail: firstname.lastname@example.org.
Financial Disclosure The authors did not report any potential conflicts of interest.