McDonald and Shirodkar Cerclage
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Direct answer
McDonald and Shirodkar cerclage are two ways of placing a suture around the cervix to prevent preterm birth. McDonald cerclage is a less invasive, more commonly used transvaginal purse-string stitch at the cervicovaginal junction. Shirodkar cerclage needs vaginal flap dissection and places the suture at the internal os. Elective placement is usually done around 12 to 14 weeks.
What you must remember
- Indication: painless cervical dilatation in the second trimester with a history of second-trimester loss or preterm birth, meaning cervical insufficiency.
- Ultrasound-indicated use: may be considered in women with a previous preterm birth and a short cervix below about 25 mm before 24 weeks.
- Timing: elective placement at about 12 to 14 weeks; rescue placement when the cervix dilates before 24 weeks with membranes intact.
- Contraindications: active labour, ruptured membranes, intrauterine infection, bleeding and fetal death.
- Complications: infection, bleeding, preterm labour and membrane rupture; Shirodkar adds risk of bladder or ureteric injury.
- Removal: usually at 36 to 37 weeks, or at the onset of labour.
Comparing the two techniques
Both procedures aim at the same goal, but the approach, level and invasiveness differ. The table lists the points that are most often tested.
| Feature | McDonald | Shirodkar |
|---|---|---|
| Approach | Transvaginal purse-string stitch | Vaginal flaps dissected to create bladder and rectal spaces |
| Level of suture | Cervicovaginal junction | Internal os |
| Invasiveness | Less invasive | More invasive, with bladder injury risk |
| Removal | Suture cut and removed near term | Removed near term, or left in situ if caesarean is planned |
McDonald is the usual first choice because it avoids flap dissection. Shirodkar is reserved for situations where a higher placement at the internal os is preferred.
Vignettes usually give the history of cervical insufficiency first, then ask which technique or timing is correct. The contraindications are the same for both techniques, and removal is usually at 36 to 37 weeks, although a Shirodkar suture may be left in place when elective caesarean is planned. Both techniques need a sterile speculum examination, exclusion of infection and a documented gestation before placement.
Where the exam tries to catch you
Cerclage questions test the contraindications, the removal timing and the difference between the two techniques.
- Trap: Placing a cerclage in a woman with ruptured membranes or in labour. Correct: Both are absolute contraindications to elective cerclage.
- Trap: Assuming cerclage is removed at 20 weeks. Correct: Removal is at 36 to 37 weeks or at the onset of labour.
- Trap: Choosing Shirodkar for a routine case. Correct: McDonald is less invasive and is the usual first choice for most women.
Frequently asked questions
What is the difference between McDonald and Shirodkar cerclage?
McDonald cerclage is a transvaginal purse-string suture at the cervicovaginal junction, while Shirodkar cerclage needs vaginal mucosal flap dissection and placement at the internal os. McDonald cerclage is the less invasive approach. Both are tied in the second trimester and removed near term.
When is cervical cerclage removed?
Cervical cerclage is usually removed at 36 to 37 weeks of gestation or when labour begins. Removal before term can precipitate preterm labour. Removal timing is planned in advance and recorded.
What complications follow cervical cerclage placement?
Infection, bleeding, preterm labour and premature rupture of membranes are the main complications of cervical cerclage. Shirodkar cerclage carries an additional risk of bladder or ureteric injury during flap dissection. Cerclage is avoided in the presence of active infection.
What is the best-recognised indication for cerclage?
The best-recognised indication is painless cervical dilatation in the second trimester in a woman with a history of second-trimester loss or preterm birth. Emergency placement when the cervix has dilated also falls under this indication. A short cervix alone in a singleton with no history is a weaker indication.