Works for One, But Not for Twins

17P injection for preterm birth does not reduce risk of early birth for women with twins

(RxWiki News) Women with a short cervix and women carrying twins are at higher risk for preterm birth. Women with both have an even higher likelihood of giving birth early.

A recent unpublished study investigated whether a medication might reduce the risk of preterm birth for women carrying multiples. The study was presented at a recent pregnancy conference.

Receiving an injection called 17P can reduce the risk of preterm birth among women carrying a single child.

When tested in women with twins and short cervixes, however, 17P didn't appear to help the same way. It may have actually hurt.

"Attend all prenatal visits."

The study, led by Marie Victoire Senat, MD, of the Department of Obstetrics and Gynecology at Faculté de Medecine Paris XI in France, tested whether giving 17 alpha-hydroxyprogesterone caproate (17P) to women with short cervixes carrying twins prevented the risk of preterm birth.

Over a four year period, 165 adult women carrying twins in otherwise healthy pregnancies were enrolled in the study if they had a cervix shorter than 25 mm as measured by a transvaginal ultrasound. The women were all between their 24th and 32nd week of pregnancy.

Half the women received an injection of 500 mg of 17P twice a week until their 36th week of pregnancy or until they gave birth. The other half received no 17P.

Among the women who received 17P, the average number of days that passed from their enrollment until they gave birth was 45 days, compared to 51 days among those who did not receive 17P.

However, this six day difference was not wide enough to conclude that the 17P made any difference.

In fact, looking at the overall preterm births, 29 percent of the women receiving 17P gave birth before the 32nd week of pregnancy, compared to 12 percent of the women who did not receive 17P.

The birth weight of the first twin was not significantly different among the women in either group. The first twin was an average 4.67 pounds among women who received 17P and 4.88 pounds among women who didn't receive 17P.

However, the second twins of the women receiving 17P tended to be smaller than the second twins of women not receiving 17P. The average second twin weight in the 17P group was 4.60 pounds, compared to 4.91 in the non-17P group.

The researchers concluded that giving 17P to the women did not help reduce the risk of preterm birth and might actually have caused some harm by increasing preterm births and/or reducing the second twin's birth weight.

The study was presented February 14 at the Society for Maternal-Fetal Medicine's annual meeting, The Pregnancy Meeting, in San Francisco.

Because the study has not yet been published in a peer-reviewed journal, its results should be regarded as preliminary and still require review by researchers in the field. Information was unavailable regarding funding and conflicts of interest.

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Review Date: 
February 13, 2013