Cervical Suture May Not Prevent Preterm Birth for Some Women
According to a recent study, one method commonly used to help prevent preterm births – stitching the cervix closed - is actually ineffective for some women.
Up to 12 percent of all deliveries in the developed world are considered preterm births – occurring before 37 weeks of gestation. Roughly a quarter of these births occur early without any known reason. Infants born prematurely are more likely to need additional medical care after delivery. Those born before 33 weeks have a greater risk of disability or even death. For these reasons, researchers are searching for the causes of early births and ways to help prevent their occurrence.
In an effort to delay birth, a stitch or suture encircling the cervix is used to keep the cervix closed in women with certain high-risk conditions. For example, evidence shows cervical cerclage, as the procedure is called, is effective for women with a history of a weak or "incompetent" cervix. Women with a weak cervix experience recurrent painless second trimester miscarriages because the cervix opens from the pressure of the weight of the fetus. By sewing the opening to the uterus closed, birth is delayed until the suture is removed during the ninth month.
Without solid evidence of its success, the procedure is also sometimes used in women known to have short cervixes. Normally, the cervix is about 25 mm in length, but some women have a shorter cervix (less than 15 mm). These women are at a higher risk of delivering prematurely. So physicians believed, with some uncertainty, that stitching the cervix closed would help delay birth. But now a study published in The Lancet earlier this year shows a cervical suture is actually ineffective in these women.
In the study, over 47,000 women with a pregnancy involving one fetus underwent routine ultrasound screening between 22 and 24 weeks. Of these women, 253 were found to have a short cervix. From this group, half of the women were assigned to have a cervical suture. The other half received standard care. All of the women with a short cervix were given two injections of dexamethasone to help promote fetal lung development in the event of preterm birth. Surprisingly, the rate of preterm birth before 33 weeks did not differ significantly between the two groups (22% in the cervical suture group and 26% in the control group).Although the size of this study was small, the results suggest a cervical suture is ineffective at preventing preterm births in women with short cervixes. Despite these results, some physicians may still recommend cervical cerclage because no alternatives exist. This is especially the case for women with a very short cervix and before 23 weeks of pregnancy (the critical age for a fetus' hope of survival outside the womb). A larger study is now underway and will hopefully bring more certainty to such decisions.
September 2004 Update