Does 17-α-hydroxyprogesterone caproate affect fetal biometry and birth weight in twin pregnancy?

Objective: Increasingly, maternal administration of 17-α- hydroxyprogesterone caproate (17-OHPC) is utilized to prevent preterm birth, but the fetal safety of 17-OHPC is still a matter of concern. This study aimed to assess whether exposure to 17-OHPC during the second and third trimesters of pregnancy affects fetal biometry in twin gestations. Methods: This study included a subset of women with a twin pregnancy who had been previously included in a randomized clinical trial comparing the effectiveness of 17-OHPC and placebo on neonatal outcomes and preterm birth rates in multiple pregnancy. In the present study, the individual growth patterns of femur length, head circumference and abdominal circumference were compared between fetuses of women who had been randomized to receive weekly injections of either 17-OHPC (n = 52) or placebo (n = 58) at between 16-20 and 36 weeks' gestation. Results: The three biometric variables assessed developed similarly in fetuses in both the group exposed to 17-OHPC and the placebo group during the second half of pregnancy. Birth weight adjusted for parity and fetal sex was also comparable between groups. Conclusion: The use of 17-OHPC has no adverse effects on fetal biometry and birth weight in twins.