Preterm delivery and growth restriction in multifetal pregnancies reduced to twins.

Gestation at delivery, birthweight and pregnancy outcome of surviving fetuses from 127 multifetal pregnancies undergoing embryo reduction to twins were compared to 354 chromosomally normal non-reduced dichorionic twin pregnancies. First-trimester embryo reduction was carried out by intracardiac injection of KCl. In 16 (12.6%) of the 127 multifetal pregnancies reduced to twins, there was miscarriage of both fetuses before 24 weeks of gestation. The median interval between reduction and fetal loss was 5 weeks (range 1-12). In livebirths, the median gestation at delivery was 36 weeks (range 24-41) and the median difference in birthweight from the appropriate mean was -0.94 SD (range -3.89-1.73 SD). Both fetal loss before 24 weeks and the interval between embryo reduction and delivery were significantly associated with the gestation at reduction (r = 0.40, P < 0.001 and r = -0.57, P < 0.001 respectively). In the pregnancies reduced to twins compared to the non-reduced twins, the percentage of miscarriages was higher (12.6 compared to 2.5%; chi 2 = 19.2, P < 0.001), the median gestation at delivery was lower (36 compared to 37 weeks; t = -1.74, P < 0.05), and the median birthweight deficit was greater (-0.94 compared to -0.65 SD: t = -4.1, P < 0.001).