(HealthDay News) – 17 alpha-hydroxyprogesterone caproate (17P) is ineffective in preventing preterm delivery in women with a short cervix asymptomatically carrying twins, and may actually be harmful, according to a study presented at the annual meeting of the Society for Maternal-Fetal Medicine, held from Feb. 11–16 in San Francisco.

Marie Victoire Senat, from Hopital Bicêtre in Paris, and colleagues randomized (1:1) women (≥18 years and carrying twins between 24 + 0 through 31 + 6 weeks of gestation) to receive 500mg of intramuscular 17P twice weekly until 36 weeks or preterm delivery, whichever occurred first (82 women), or to no treatment with 17P (control group; 83 women). All selected women were asymptomatic but presented a cervical length <25mm as measured by routine transvaginal ultrasound.

The researchers found no significant difference between the 17P and controls group in median (Q1 to Q3) time to delivery (45 [26–62] and 51 [36–66] days, respectively; mean difference, −7). There was a significant increase in the rate of preterm deliveries before 32 weeks of gestation with treatment with 17P (29% vs. 12%; P=0.007), but not before 37 weeks of gestation (80% vs. 77%; P=0.70) or 34 weeks of gestation (44% vs. 28%; P=0.10). The two groups had no significant difference in median (Q1–Q3) birth weight for twin 1 (2,120 [1,750–2,471] g and 2,215 [1,982–2,535] g, respectively; P=0.06) but differed significantly for twin 2 (2,090 [1,540–2,425] and 2,230 [1,985–2,535] g, respectively; P=0.027).

“We found that 17P was not effective in women with twin pregnancies and a short cervix (defined as less than 25 mm between 24 and 32 weeks),” a coauthor said in a statement. “We actually seemed to have found an increase in the rate of preterm delivery before 32 weeks in the treatment group when compared to the non-treatment group.”

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