Triplet pregnancies reduced to singletons see better birth outcomes vs. reduction to twins

Compared with triplet pregnancies reduced to singletons, those reduced to twins had lower fetal survival rate, younger gestational age at birth, lower birth weight and greater risk of preterm birth, according to findings of a meta-analysis.

Fetal reduction was developed in the 1980s to decrease pregnancy complications, and studies have shown that reduction from triplet pregnancy to either singleton or twin pregnancy resulted in better outcomes compared with expectant management, Kamran Hessami, MD, a postdoctoral research fellow in the department of obstetrics and gynecology at Baylor College of Medicine, and colleagues wrote.

“However, what was not completely clear was whether fetal reduction of triplet pregnancies to singletons might further improve pregnancy outcomes when compared to reduction of triplets to twins,” the researchers wrote in the American Journal of Obstetrics and Gynecology.

Hessami and colleagues identified 10 studies of 2,392 triplet pregnancies published between 2012 and 2020. Of these, 1,903 were reduced to twins (RTT) and 489 were reduced to singletons (RTS). Additionally, 2,324 patients in eight studies underwent fetal reduction by potassium chloride injection and 68 patients in two studies underwent transvaginal aspiration.

RTT increases risk for adverse outcomes

Overall, the fetal survival rate was significantly lower in RTT pregnancies compared with RTS pregnancies (OR = 0.61; 95% CI, 0.4-0.92; 95% prediction interval [PI], 0.36-1.03). However, the type of fetal reduction technique used did not significantly affect fetal survival.

“Subgroup analyses revealed that RTT among [dichorionic triplet] pregnancies has lower survival and neonatal outcomes, which is not surprising, consistent with long known differences in outcomes between monochorionic [and] dichorionic twins,” Hessami and colleagues wrote.

RTT pregnancies also had significantly lower gestational age at birth (mean difference [MD] = –2.2; 95% CI, –2.8 to –1.61; 95% PI, –4.27 to –0.14) and lower birth weight (OR = 8.76; 95% CI, 5.56-13.8; 95% PI, 4.6-16.67).

The researchers identified a greater risk for preterm birth before 34 weeks’ gestation (OR = 3.04; 95% CI, 1.45-6.36; 95% PI, 0.54-17.18) and 32 weeks’ gestation (OR = 2.14; 95% CI, 1.02-4.49; 95% PI, 0.64-7.13) with RTT pregnancies compared with RTS pregnancies.

Triplet pregnancies RTT and RTS had a similar risk for pregnancy loss before 24 weeks’ gestation (OR = 0.89; 95% CI, 0.58-1.38; 95% PI, 0.54-1.48) and neonatal death (OR = 0.56; 95% CI, 0.1-3.21).

Further analysis showed there was a significantly lower live birth rate in expectantly managed dichorionic triplet pregnancies compared with RTS (RR = 0.74; 95% CI, 0.59-0.93), and no significant difference between triplet pregnancies expectantly managed and RTT.

Applying findings to practice

Hessami and colleagues emphasized that clinicians’ decision on reducing pregnancies should be informed by the risks and benefits elucidated in their meta-analysis.

“The choice between reductions to singleton or twin gestations can be dependent on multiple factors such as parents’ preference, fertility status, chorionicity, gestational age at reduction and abnormal nuchal translucency and/or diagnosed genetic and structural anomalies,” they wrote.

In practice, they indicated that performing ultrasound exams of all fetuses as well as genetic testing should be routine procedures before all fetal reductions to reduce poor outcomes.