Cerclage: Should we be doing them?
We've been doing cerclage for roughly half a century—but where's the evidence that it prevents preterm birth? The authors make the case for limiting this surgery to select patients, cautioning that for multiple gestations, it might just make things worse.
Does cerclage actually prevent miscarriage and pre-term birth (PTB) as intended? Our purpose here is to examine the scientific evidence that supports or refutes that premise, which as you will see suggests the procedure should only be done sometimes-and only in specific situations. The evidence also suggests a need to cut back on the estimated 40,000 cerclages placed each year in the United States-a number that translates into about 1% of pregnancies receiving cerclage annually.
One originator of this procedure in the early 1950s, Dr. V.N. Shirodkar, envisioned cerclage as appropriate for "women who abort repeatedly between the 4th and 7th month...where one can, by repeated internal examinations... find that the cervix is gradually yielding."1 Another pioneer, Dr. I.A. McDonald (Figure 1), saw cerclage as appropriate for "[women with] prior second-trimester miscarriages.... [who] presented with dilatation of the cervix and bulging of the forewaters during the second trimester."2 These investigators therefore agreed that two indications were needed for cerclage: a poor obstetrical history of repeated second-trimester losses, and cervical changes in the current pregnancy.
Diagnosis of cervical insufficiency and indications for cerclage
The diagnosis of cervical insufficiency is based on a history of painless dilation leading to recurrent second-trimester losses (STL).3 Therefore cervical insufficiency is one extreme on the continuum of PTB.4 Current proposed possibleindications for suturing the cervix closed include:
- history of cervical insufficiency or a high risk for PTB;
- ultrasound (transvaginal ultrasound [TVU]) measurements of cervical length (CL) less than 25 mm prior to 24 weeks during the current pregnancy;
- physical exam (bimanual or speculum) revealing dilation or shortening of the cervix-or both;
- multiple gestations including twins or higher-order multiple gestations; and
- combinations of the above.
The terminology used in the past to describe the indications for cerclage has been very confusing. We avoid using terms like prophylactic, elective, salvage, therapeutic, urgent, emergent, and rescue. Instead, we recommend terms that more accurately describe the clinical situation, like history-indicated or U/S-indicated (Table 1).
History-indicated cerclage only helps a minority
Unfortunately, none of the three randomized trials evaluating history-indicated cerclage have focused on women with classical cervical insufficiency.5-7 Of the women studied, the only ones who appear to benefit from cerclage are those with three or more prior STL or prior PTBs.7 In this limited population, the number of PTBs declined by about 40% with cerclage compared to similar women who did not receive cerclage. Women with two STLs can also be considered for history-indicated cerclage, but there's no evidence that this does any good. The best time to place history-indicated cerclage is at around 11 to 13 weeks, before cervical changes occur.