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
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