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Introduction Forceps Delivery1

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Introduction Forceps Delivery1

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   The Role For Emergency Cerclage: What Does the Data Really Show?
E.R. Norwitz
Division of Maternal-Fetal Medicine, Department of Obstetrics, Gynecology and Reproductive Biology, Brigham & Women's
Hospital, Harvard Medical School, Boston, Massachusetts, U.S.A.
Introduction
Cervical incompetence is defined as the inability to support a pregnancy to term due to a functional or
structural defect of the cervix (1). It is a clinical diagnosis characterized by acute, painless dilatation of the
cervix usually in the mid-trimester culminating in prolapse and/or premature rupture of the membranes
(PROM) with resultant preterm and often previable delivery. Cervical cerclage has become the mainstay for
the management of cervical incompetence.
Cervical Anatomy
Embryologically, the body and cervix of the uterus are derived from fusion and recanalization of the
                                                                           th
                                                                              month of pregnancy. Histologically,
the cervix consists of fibrous connective tissue, muscle, and blood vessels. Muscular connective tissue
constitutes approximately 15% of the cervical stroma, but is not uniformly distributed throughout the cervix,
constituting approximately 30%, 18%, and 7% of the upper, mid, and lower thirds of the cervix, respectively
(2). Conversely, the fibrous connective tissue content of the cervical stroma increases as one moves from the
external os to the uterine corpus, and it this component that is believed to confer tensile strength to the cervix.
Defects in tensile strength are thought to lead to premature cervical dilatation and pregnancy loss.
Etiology

abnormalities (cervical hypoplasia, in utero diethylstilbestrol [DES] exposure), traumatic abnormalities
(prior surgical or obstetric trauma), and connective tissue abnormalities (Ehlers-Danlos syndrome). Of note,
a history of first trimester abortion does not appear to be a risk factor for cervical incompetence if the
abortion was performed by a skilled operator using local anesthesia and laminaria (3-5).
Incidence
It is estimated that cervical incompetence will complicate anywhere from 0.1% to 2% of all pregnancies
(1,6-8), and is thought to be responsible for approximately 15% of habitual immature deliveries between 16
and 28 weeks of gestation (9).
Indications
Suspected cervical incompetence remains the only acceptable indication for cervical cerclage. Indications
can be classified as follows:
(1) Prophylactic (elective) cervical cerclage is indicated in asymptomatic women with a history of prior
pregnancy loss and/or preterm delivery due to cervical incompetence. This is because the probability of
recurrence in a subsequent pregnancy is 15-30% (1,9). Prophylactic cervical cerclage may be placed prior to
pregnancy, but is more commonly placed between 10-16 weeks’ gestation.
(2) Asymptomatic women with sonographic evidence of cervical shortening and/or funneling may also
benefit from cervical cerclage (often called urgent cerclage), although the data in this regard is
controversial. There are several retrospective studies suggesting that cervical cerclage in asymptomatic
women with short cervical length on endovaginal ultrasound may improve perinatal outcome (10-13). These
studies reported an overall reduction in the incidence of preterm delivery in women identified as having a
short cervix by transvaginal sonography before 24 weeks’ gestation and subsequently treated with cerclage
to approximately 10% of controls. However, more recent studies suggest that cerclage does not prevent
preterm delivery in women at high-risk for preterm birth on the basis of cervical shortening (14,15).
Moreover, one study showed a higher rate of preterm PROM in women who received a cerclage as compared
with those without cerclage (15). Further studies are awaited to clarify this issue.
(3) Emergency (salvage) cervical cerclage refers to placement of a cerclage in the setting of significant
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cervical dilatation and/or effacement prior to 28 weeks’ gestation and in the absence of labor. It is this entity
which will discussed in further detail below.
Contraindications to Emergency Cervical Cerclage
Absolute contraindications to emergency cerclage are summarized in Table 1. Factors such as placenta
previa, a mucopurulent cervical discharge with membrane opacification, fetal membranes prolapsing
through the cervical os, and/or intrauterine fetal growth restriction (IUGR) may be regarded as relative
contraindications. ACOG supports cervical cerclage placement up to 28 weeks’ gestation (16). However,
many practitioners would not recommend emergent cervical cerclage placement beyond the limit of fetal
viability (i.e., 24 weeks’ gestation), because the potential for harm likely outweighs the potential benefit
(17).
Complications of Emergency Cervical Cerclage
Complications of emergency cerclage increase with increasing gestational age and cervical dilatation (18),
and are summarized in Table 2. In general, cervical cerclage is associated with increased obstetric
interventions, including higher rates of admission to hospital, long-term tocolysis, induction of labor, and
cesarean delivery (8,19). Puerperal infection occurs in approximately 6% of patients with cerclage, which is
twice as common as the incidence in gestational age-matched controls without cerclage (8,19).
Technical Considerations
(1) Preoperative considerations. An ultrasound should be performed to exclude gross structural anomalies
(such as anencephaly) and/or fetal demise. Written consent should be obtained.
(2) Amniocentesis? Intraamniotic infection is an absolute contraindication to cervical cerclage, and the
presence of bacteria on Gram stain or a positive culture from preoperative amniocentesis is associated with a
failure rate of >90% (20). Romero et al (21) showed that microbial invasion of the amniotic fluid can be
expected in more than 50% of patients with cervical dilatation >2 cm between 14 and 24 weeks’ gestation.
Importantly, the spectrum of cultured organisms in their study included Ureaplasma urealyticum,
Gardenerella vaginalis, Fusobacterium sp., Mycoplasma hominis, and Candida albicans, all organisms
thought to be normal flora of the lower genital tract. All patients in this series with amniotic infection
confirmed by amniocentesis delivered within 1 week. Despite these data, preoperative amniocentesis in
asymptomatic parturients with cervical incompetence should not be regarded as an absolute prerequisite for
emergency cerclage placement. The data regarding cervicovaginal cultures and the efficacy of emergency
cerclage is similarly controversial.
(3) Intraoperative considerations. Many practitioners will recommend an observation period of 12-24
hours before placement of an emergency cerclage to exclude preterm labor, ruptured membranes, and
chorioamnionitis (22), although it is not clear that is necessary. Confirmation of fetal viability is required
both immediately before and after the procedure, either by auscultation or by ultrasound. Regional
anesthesia is preferred, because of the decreased maternal morbidity as compared with general endotracheal
anesthesia. Prophylactic tocolysis may be used to inhibit transient uterine contractions associated with
cerclage placement, but there is no objective evidence that tocolysis improves outcome. Moreover, although
there are no trials to support their use in prophylactic cerclage procedures, most series reporting higher fetal
salvage rates with emergency cerclage have used perioperative broad-spectrum antibiotics with a view to
decreasing the risk of intra-amniotic infection (refer Table 3).
(4) Prolapsing membranes. If the fetal membranes are found to be prolapsing through the external os, the
risk of iatrogenic rupture of the fetal membranes may be as high as 40-50%. Trendelenburg position (23),
filling the bladder (24), placement of a 30-mL Foley catheter (25) or moistened sponge forceps into the
cervical os (26), and/or therapeutic amniocentesis (27-29) can be used to reduce the fetal membranes prior to
cerclage placement, with variable success.
(5) Choice of cervical cerclage. There are no well-designed, prospective, randomized, controlled clinical
trials comparing Shirodkar and McDonald cerclage. As such, the decision of which technique to use can be
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left to the discretion of the operator. Under certain circumstances, however, one or other technique may be
preferable. For example, if the cervix is very short or lacerated, a Shirodkar cerclage may be technically
easier to place.
(6) Postoperative recommendations. Weekly or biweekly follow-up visits are probably sufficient in the
absence of clinical symptoms. Cervical assessment may be by bimanual examination or by ultrasound.
Bedrest and “pelvic rest” (no coitus, tampons, or douching) are usually recommended until a favorable
gestational age is reached, but without proven benefit. In the absence of obstetric complications, the cerclage
is usually removed electively in the office at around 37 weeks’ gestation.
Efficacy of Emergency Cervical Cerclage: What Does the Data Really Show?
It is generally accepted that cerclage placement for cervical incompetence is best performed prior to cervical
dilatation and effacement. At least two studies have reported a lower success rate (50% and 59%) with
emergency cerclage as compared with prophylactic cerclage (86% and 81%), although in neither studies was
the number of cases sufficient to reach statistical significance (30,31). If emergency cerclage procedures
truly have a lower success rate, it is tempting to conclude that the cerclage was placed too late. However, an
equally plausible explanation would be that some prophylactic cerclages are placed in women who do not
need them and, as such, are bound to have more favorable outcomes.
It is commonly believed that emergency cerclage may be the only hope for prolonging gestation in
parturients with advanced cervical changes in the second trimester with or without prolapsed membranes
(“eminence-based medicine”). However, emergency cerclage is a surgical procedure with well-defined
operative risks. Whether such an approach is superior to bedrest and expectant management remains unclear
(evidence-based medicine). The weight of evidence in the published literature suggests that emergency
cerclage is associated with a fetal survival rate of 22-100% (Table 3). However, such data comes exclusively
from retrospective descriptive studies. There are as yet no published randomized controlled trials (RCT)
specifically addressing the issue of emergency cerclage. Some authors would argue that such an RCT would
be unethical as it would deprive patients of standard therapy (32); others would argue that it is unethical for
us to continue to pretend that emergency cerclage has ever been proven to be beneficial in a rigorous,
scientific fashion. In the absence of incontrovertible evidence demonstrating a benefit, emergency cervical
cerclage should be used judiciously and only after extensive and comprehensive patient counseling.
Conclusions
Emergency cervical cerclage remains an important part of the obstetric armamentarium for the management
of cervical incompetence. However, it is a surgical procedure without proven benefit and with well-defined
operative risks. As such, until adequate clinical trials are available demonstrating a clear benefit, emergency
cerclage should be used judiciously and only after extensive and comprehensive patient counseling.
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                 Table 1. Absolute Contraindications to Emergency Cervical Cerclage

                        Table 2. Complications of Emergency Cervical Cerclage

                                                   ¶
Table 3. Efficacy of Emergency Cervical Cerclage

								
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