Keywords : hCG, false positive, GTN
Selective feticide of an abnormal twin is a desirable intervention but the timing of this intervention s controversial.
A 29 year old lady conceived by IVF after secondary subfertility.
Booking scan confirmed a dichorionic twin pregnancy and a fetal anomaly scan at 19 weeks revealed the second twin to have holoprosencephaly (Figure 1). She was referred to fetal medicine centre where the abnormality was confirmed and had selective feticide of the second twin at 32 weeks. Two weeks later she had spontaneous rupture of membranes, followed by the onset of labor and vaginal delivery of a live female baby weighing 1.8 kg and a stillborn female baby weighing 1.04 kg at 34 weeks.
The learning point in this case is the timing of the selective feticide.
The risks of selective feticide if done in the first and second trimesters are chorioamnionitis, premature rupture of membranes and fetal loss in 5-10% cases 1. Obviously these consequences are less damaging as pregnancy advances.
The surviving twin is also at risk of cerebral palsy. In a large cohort study in UK of twins where one twin died, the incidence of cerebral palsy in the survivor in an unlike sex twin was 29/1000 2, whereas the incidence of cerebral palsy in the general population is about 2-3/ 1000 live births 3. It stands to reason that more mature the surviving twin is and lesser the time interval between the demise of one twin and the delivery, the lesser is the risk to the surviving twin.
On the other hand, delaying the procedure too late in the third trimester increases the risk of pregnancy complications like pre-eclampsia, pregnancy induced hypertension, polyhydramnios, gestational diabetes, maternal discomfort etc 4.
Labor usually sets in within three weeks following death of one twin in the majority of the cases 4.
Hence 32 weeks was chosen for the selective feticide.
