Late selective termination: comparing late second and third trimester procedures

To compare outcome of selective termination (ST) performed in the late 2nd and 3rd trimesters and to identify factors associated with preterm birth (PTB) following procedure. A retrospective cohort study of late ST (≥20 weeks of gestation) performed in dichorionic twins at a single tertiary centre. Outcomes were compared between late 2nd trimester (200/7-276/7 weeks) and 3rd trimester (≥ 280/7 weeks) STs. An additional comparison was conducted between term and preterm births (< 37 weeks) following procedure. A total of 81 dichorionic pregnancies were included. The median gestational age at time of procedure was 31 weeks (range 20.2-35.2 weeks). There were no pregnancy losses, but 16% (13/81) experienced complications. There were no statistically significant differences in PTB rate between the late 2nd and 3rd trimester groups. The late 2nd trimester group had a significantly higher median birthweight centile (51.5th vs 28th centile, P 0.002) and a lower rate of Caesarean delivery (26.9% vs 63.6%, P 0.004).There were higher rates of previous PTB, reduction of the presenting twin and cervical length below 35 mm in the PTB group compared to the term birth group (12.8% vs 0%, P 0.037, 55.3% vs 11.8%, P < 0.001 and 75.8% vs 24.2%, P 0.01). There was no statistically significant difference in the rate of 2nd trimester procedure between term and PTB groups. Multiple regression revealed that reduction of the presenting twin and cervical length below 35 mm at procedure were both independently associated with PTB following a late ST (OR 8.7, P 0.001, 95% CI 2.5-29.8 and OR 3.8, P 0.015, 95% CI 1.3-11, respectively). Late 2nd trimester ST results in higher birthweight centile, a lower rate of Caesarean delivery with similar PTB rate, compared to 3rd trimester ST. A cervical length below 35 mm and reduction of the presenting twin are independently associated with PTB following procedure. These findings may be clinically important when determining the optimal gestational age to perform a late ST.