Abstract
BackgroundThe rationale for fetal surveillance in monochorionic twin pregnancies is timely intervention to prevent the increased fetal/perinatal morbidity and mortality attributed to twin–twin transfusion syndrome and intrauterine growth restriction. We investigated the residual risk of fetal death after viability in otherwise uncomplicated monochorionic diamniotic twin pregnancies.Methods and FindingsWe searched an electronic database of 480 completed monochorionic pregnancies that underwent fortnightly ultrasound surveillance in our tertiary referral fetal medicine service between 1992 and 2004. After excluding pregnancies with twin–twin transfusion syndrome, growth restriction, structural abnormalities, or twin reversed arterial perfusion sequence, and monoamniotic and high-order multiple pregnancies, we identified 151 uncomplicated monochorionic diamniotic twin pregnancies with normal growth, normal liquor volume, and normal Doppler studies on fortnightly ultrasound scans. Ten unexpected intrauterine deaths occurred in seven (4.6%) of 151 previously uncomplicated monochorionic diamniotic pregnancies, within 2 wk of a normal scan, at a median gestational age of 34+1 wk (weeks+days; range 28+0 to 36+3). Two of the five cases that underwent autopsy had features suggestive of acute late onset twin–twin transfusion syndrome, but no antenatal indicators of transfusional imbalance or growth restriction, either empirically or in a 1:3 gestation-matched case–control comparison. The prospective risk of unexpected antepartum stillbirth after 32 wk was 1/23 monochorionic diamniotic pregnancies (95% confidence interval 1/11 to 1/63).ConclusionDespite intensive fetal surveillance, structurally normal monochorionic diamniotic twin pregnancies without TTTS or IUGR are complicated by a high rate of unexpected intrauterine death. This prospective risk of fetal death in otherwise uncomplicated monochorionic diamniotic pregnancies after 32 wk of gestation might be obviated by a policy of elective preterm delivery, which now warrants evaluation.
Highlights
Monochorionic diamniotic (MCDA) twin placentation occurs in one in every 400 pregnancies, and is characterised by placental vascular anastomoses and interfetal transfusion [1]
We investigated the residual risk of fetal death after viability in otherwise uncomplicated monochorionic diamniotic twin pregnancies
Structurally normal monochorionic diamniotic twin pregnancies without twin–twin transfusion syndrome (TTTS) or intrauterine growth restriction (IUGR) are complicated by a high rate of unexpected intrauterine death
Summary
Monochorionic diamniotic (MCDA) twin placentation occurs in one in every 400 pregnancies, and is characterised by placental vascular anastomoses and interfetal transfusion [1]. MCDA twins are considered high risk by virtue of their 3- to 5-fold increased perinatal morbidity and mortality compared to dichorionic (DC) twins. This is largely attributed to twin–twin transfusion syndrome (TTTS), which occurs in 15%–20% of MCDA twin pregnancies, and discordant intrauterine growth restriction (IUGR), which complicates an additional 25% [1,2,3,4,5]. The rationale for fetal surveillance in monochorionic twin pregnancies is timely intervention to prevent the increased fetal/perinatal morbidity and mortality attributed to twin–twin transfusion syndrome and intrauterine growth restriction. The researchers studied the records of one United Kingdom hospital that specializes in fetal care over a 12-year period (from 1992 to 2004) and looked at the clinical details and ultrasound scan records
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