Birth outcomes of twins after multifetal pregnancy reduction compared with primary twins

Background The introduction of assisted reproductive technology and the trend of increasing maternal age at conception have been responsible for a significant rise in the incidence of multiple pregnancies. Multiple pregnancies bear several inherent risks for both mother and child. These risks increase with plurality and type of chorionicity. Multifetal pregnancy reduction is the selective abortion of one or more fetuses to improve the outcome of the remaining fetus(es) by decreasing the risk of premature birth and other complications. Objective This study compares the birth outcomes of trichorionic triplets reduced to twins with trichorionic triplets and primary dichorionic twins. The added value of this study is the comparison with an additional control group, namely primary dichorionic twins. Study design This is a retrospective cohort study. Data from January 1990 till November 2016 were collected from the East Flanders Prospective Twin Survey, one of the largest European multiple birth registries. Eigthy-five trichorionic triplet pregnancies (170 neonates) undergoing multifetal pregnancy reduction (MPR) to twins were compared to 5,093 primary dichorionic twin pregnancies (10,186 neonates) and 104 expectantly managed trichorionic triplet pregnancies (309 neonates). The outcomes are gestational age at delivery, birth weight, and small for gestational age. Results Pregnancy reduction from triplets to twins is associated with a higher birth weight (+365.44 g, 95%CI [222.75, 508.14 g], p < .0001) and longer gestational age (1.7 weeks, 95%CI [0.93, 2.46], p< .0001) compared to ongoing trichorionic triplets, adjusted for sex, parity, method of conception, birth year, and maternal age. A trend towards a lower risk of SGA is observed. Reduced triplets have, on average, a lower birth weight (-263.12 g, 95%CI [-371.80, -154.44 g], p < .0001), and a shorter gestational age (-1.13 weeks, 95%CI [-1.70, -0.56], p=0.0001) compared to primary twins. No statistically significant difference between primary twins and reduced triplets that reach 32 weeks of gestation is observed. Conclusion Multifetal pregnancy reduction from trichorionic triplets to twins significantly improves birth outcomes. This suggests that MPR of trichorionic triplets to twins is medically justifiable. However, the birth outcomes of primary twins before 32 weeks of gestation are still better in comparison with reduced triplets. The process of MPR includes at least one fetal death by definition, therefore prevention of higher-order pregnancies is preferred.