Cervical Insufficiency

Three cerclage settings, three risk profiles - History-indicated (prophylactic) cerclage is placed at 12-14 weeks on a closed cervix. Ultrasound-indicated cerclage goes in before 24 weeks for a cervix under 25 mm with a history of prior spontaneous preterm birth. Physical-exam-indicated (rescue) cerclage is for advanced dilation without contractions before 24 weeks - that one has the least margin and the most risk.

Neuraxial is the usual choice - Spinal or epidural needs to cover the cervical dermatomes (T10-L1) plus vaginal and perineal (S2-S4). There is little outcomes evidence favoring neuraxial over general; a retrospective series found no fetal outcome difference between general and epidural, and a small randomized comparison of spinal versus general for prophylactic Shirodkar placement found no difference in postoperative plasma oxytocin or uterine activity.

Guard the membranes - Rupture of the fetal membranes is the major risk of cerclage. Bulging membranes are reduced with Trendelenburg, tocolytics, or the direct uterine-relaxing effect of volatile agents; if the surgeon needs relaxation, that argues for a volatile-based general. Under general, avoid coughing or bucking on the tube - a rise in intra-abdominal pressure raises uterine pressure and can tear membranes during suture placement.

Treat her as pregnant - Progesterone lowers resting lower esophageal sphincter tone and delays gastric emptying, and the gravid uterus compresses the stomach, so plan aspiration prophylaxis and manage the airway accordingly. Position in left uterine displacement once gestation is past 18-20 weeks.

Protect placental perfusion - Take the usual precautions against neuraxial hypotension. In a rescue cerclage the fetus is already tenuous, and a drop in maternal pressure adds placental insufficiency on top of it.

Fetal monitoring policy varies - These fetuses are usually pre-viable, so intraoperative fetal heart rate monitoring practice differs by institution. Ask what your unit expects before the case rather than in the room.

Case profile - Dorsal lithotomy with slight Trendelenburg and the bed raised to eye level, 30-60 minutes, very low blood loss, minimal postoperative pain, no maintenance paralytic. McDonald is a purse-string at the cervicovaginal junction; Shirodkar dissects the bladder off and buries the suture, so it takes longer.

Infection is a listed complication - Cerclage risks include infection and sepsis, laceration at the suture site, and inadvertent membrane rupture, and these run higher for ultrasound- and exam-indicated placements than for history-indicated ones. Initial dilation greater than 4 cm carries a poor prognosis.

Removal - The suture comes out at 36-38 weeks before labor starts, usually in the office. If preterm labor is diagnosed it is removed then to spare the cervix; if a cesarean is planned, removal can wait until surgery.

Cervical insufficiency is painless cervical dilation in the absence of contractions or labor, from a functional or structural defect that lets the cervix ripen far from term. Causes are congenital (defective Mullerian duct development, or collagen deficiency in Ehlers-Danlos and Marfan syndromes) or acquired (obstetric laceration, conization, LEEP, forced dilation during uterine evacuation) - though in most patients the cervical change follows infection and inflammation that switches on the final pathway of parturition early.

It shows up in the mid-second or early third trimester and is a well-recognized cause of late miscarriage and preterm birth, with an incidence near 0.5% overall and 8% in women with prior mid-trimester loss. Transvaginal ultrasound shows a cervical length of 25 mm or less, or funneling of membranes into a dilated internal os. Treatment is cerclage, and that is where anesthesia gets involved.