First-trimester fetal reduction using microwave ablation in high-order pregnancies with a monochorionic component:...

To evaluate the feasibility and short-term outcomes of first-trimester ultrasound-guided microwave ablation (MWA) for selective fetal reduction in high-order multiple pregnancies containing a monochorionic component.

This retrospective single-center case series included all triplet and higher-order pregnancies with a monochorionic component undergoing first-trimester MWA between October 2023 and February 2026. Primary outcomes were technical success and pregnancy-level complications. Secondary outcomes included gestational age at delivery and neonatal outcomes.

Fifteen pregnancies (8 triplet, 5 quadruplet, 2 quintuplet) comprising 23 targeted fetuses were included. Mean gestational age at intervention was 13 + 1 weeks, with procedures performed between 11 + 3 and 14 + 4 weeks of gestation. Technical success was achieved in all targeted fetuses (23/23, 100%). One unintended intraprocedural demise of a non-target monochorionic co-fetus occurred (1/15 pregnancies, 6.7%). Among 13 completed pregnancies, 11 delivered as twins, one as triplets, and one as a singleton. Mean gestational age at delivery was 36 + 4 weeks, with deliveries occurring between 33 + 0 and 38 + 2 weeks. Twenty-six neonates were delivered, all live-born. No neonatal deaths were observed.

In high-order pregnancies containing a monochorionic component, targeted elimination of the monochorionic compartment using MWA was technically feasible and resulted predominantly in dichorionic twin gestations, with short-term outcomes that appear acceptable within the context of high-order pregnancies, although no direct comparison with other reduction techniques was performed. Larger studies with longer follow-up are warranted.