Cervical suture (Shirodkar or McDonald cerclage) is performed to reduce the incidence of spontaneous miscarriage when there is cervical incompetence. Although it can be done before conception or as an emergency during pregnancy, the procedure is usually performed electively in the second trimester. Indications include women with a history of cervical trauma, spontaneous preterm birth, preterm prelabour rupture of membranes (PPROM) or fetal loss between 16 and 34 weeks of pregnancy, and in whom transvaginal ultrasound scans at 16 and 24 weeks indicate a cervical length of less than 25 mm.
It generally takes 15-20 minutes and is performed transvaginally on a day-case basis. A non-absorbable stitch or tape is sutured in a purse-string around the cervical neck at the level of the internal os. This requires anaesthesia, since the procedure is at best uncomfortable, although the suture can often be removed without anaesthesia (usually at 36-37 weeks’ gestation unless in preterm labour); spontaneous labour usually soon follows. In patients with a grossly disrupted cervix, for example following surgery, placement of the suture via an abdominal approach may be required. Delivery is usually by elective caesarean section in these cases.
Problems and special considerations
A woman undergoing cervical suturing may be especially anxious if a previous pregnancy has ended in miscarriage. Apart from the possibility of anxiety, anaesthesia is along standard lines, bearing in mind the risks of anaesthesia in the pregnant woman and the possible effects of drugs on the fetus (see Chapter 8, Incidental surgery in the pregnant patient). Cerclage may be difficult if the membranes are bulging; the head-down position and/or tocolysis may be required to counteract this.
Management options
Both regional and general anaesthesia are acceptable for the insertion of a cervical suture, with maintenance of normal haemodynamic parameters being paramount. Many authorities advocate spinal anaesthesia as the technique of choice, since only a small amount of drug is administered, although epidural anaesthesia is also acceptable. If spinal or epidural anaesthesia is chosen, standard techniques are used. The procedure itself requires a less extensive block than caesarean section (from T8-10 down to and including the sacral roots) and thus smaller doses are required; however, the reduction is offset by the greater requirements at this early stage of pregnancy compared with the term parturient. Thus the doses required for regional anaesthesia are in the order of 75% of those used for caesarean section. Low-dose techniques have also been used, as for caesarean section; the women have more sensation (though painless) but have less motor block. Short-acting local anaesthetic agents such as prilocaine may be used to facilitate good anaesthesia for a short procedure while allowing faster discharge.
General anaesthesia may also be used; advantages include the relaxing effect of volatile agents on the uterus, and patient comfort if a steep Trendelenburg position is required. This involves administration of several drugs, and the effects on the fetus of many agents in current use are not clear (see Chapter 8, Incidental surgery in the pregnant patient). There may also be an increased risk of regurgitation and aspiration of gastric contents, depending on the gestation and severity of symptoms (see Chapter 59, Aspiration of gastric contents).
Paracervical and pudendal block and/or intravenous analgesia or sedation may also be used, but most authorities would recommend avoiding paracervical block because of potential adverse effects on uteroplacental perfusion.
Key points
• Cervical suture is usually performed in the second trimester.
• Patients may be especially anxious because of previous miscarriage.
• Standard techniques for the parturient are used; spinal anaesthesia may be preferable.
Further reading
National Institute for Health and Care Excellence. Preterm Labour and Birth. NICE Guideline NG 25.
London: NICE, 2015. www.nice.org.uk/guidance/ng25 (accessed December 2018).