Background
To investigate the indications for offering selective fetal reduction in monochorionic (MC) and dichorionic (DC) twins and to correlate obstetric outcome with the antenatal procedure.

Methods
All cases of MC and DC twins discordant for structural anomalies and for chromosomal/genetic abnormalities were included. Selective reductions performed for twin‐to‐twin transfusion syndrome or growth restriction were excluded. For DC twins, feticide was achieved using intracardiac injection of potassium chloride (KCl). For MC twins, bipolar cord occlusion (BCO), interstitial laser or radiofrequency ablation (RFA) was used.

Results
There were 121 twin pregnancies discordant for structural and chromosomal abnormalities. Only 88 (56 were MC twins and 32 were DC twins) had selective reduction. For both MC and DC twins, the leading indication for selective reduction was structural anomalies with CNS malformations the most common. For all MC fetal reduction techniques, the overall pregnancy loss rate (<24 weeks) was 8.9% with RFA having the lowest procedure loss rate (7.7%). The preterm delivery rate was lowest with reduction in DC pregnancies. The live birth rates for MC twins were >87% and 100% for DC twins.

Conclusions
Selective reduction in MC pregnancies carries an increased procedure‐related and preterm delivery rate compared with DC pregnancies. The main indication for selective reduction was structural malformations, with a predominance of CNS anomalies.