Prevention of Preterm Labour
Standard Treatment Guidelines and Essential Medicines List for South Africa, Hospital Level, Adults, Updated for the 2023 Edition
Z35.2
DESCRIPTION
Women with a previous spontaneous preterm delivery are at higher risk for preterm delivery in the next pregnancy. In certain high-risk cases, pregnancy may be prolonged by the careful consideration of either cervical cerclage or vaginal progesterone therapy.
The following high-risk women should undergo cervical screening and offered a choice of cerclage or progesterone if the cervical length is ≤25 mm:
- A history of 2nd trimester miscarriage (between 16 and 26 weeks) suggestive of cervical incompetence: (Painless dilatation with a quick labour, and birth of a live baby or fresh stillbirth) after excluding other causes of mid-trimester losses, e.g. intra-uterine death that required induction, abruptio placentae, foetal abnormalities, polyhydramnios, and medical terminations.
- Previous history of spontaneous preterm birth between 27 and 34 weeks (exclude non-spontaneous causes e.g. iatrogenic delivery for pre-eclampsia, or syphilis). No need to refer previous late preterm deliveries (34-37 weeks).
- Twin gestations (dichorionic or monochorionic), regardless of the previous history, as twin pregnancies are at increased risk (7-10 fold) of preterm labour
Do not screen for cervical length in low-risk women routinely, as it is not costeffective.
GENERAL MEASURES
Cervical length must be measured by a skilled operator using transvaginal ultrasound.
Cervical measurement can be done between 16 and 24 weeks.
A cervical length of ≤25 mm indicates a higher risk for recurrent preterm labour.
Discuss the risks and benefits of both options with the patient to make an informed shared decision of the most appropriate treatment.
MEDICINE TREATMENT
Women should be counselled that 20 cerclage procedures will prevent one preterm delivery (NNT 17 to 20) and that progesterone is successful in 1 out of every 8 cases (NNT 6 to 8), to assist them in making an informed decision.
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Consider prophylactic vaginal progesterone or cervical cerclage (MacDonald suture) for women with:
- history of spontaneous preterm birth (27-34 weeks) or mid-trimester loss (16-24 weeks), and
- cervical length ≤ 25 mm confirmed on ultrasound (16-24 weeks).
- Progesterone, PV, 200 mg daily.
- Stop treatment at 34 weeks and refer to antenatal services at primary level of care for further management.
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Consider prophylactic cervical cerclage (MacDonald suture) only for women with:
- cervical length ≤ 25 mm confirmed on ultrasound (16-24 weeks),
AND
- history of preterm prelabour rupture of membranes (PPROM), or
- history of cervical trauma.
Rescue cerclage:
- If the cervix is already open and the membranes exposed, but unruptured, consider a rescue cervical cerclage (16-27 weeks).
- Do not insert a rescue cerclage if there are contractions, active vaginal bleeding or signs of infection.
Cerclage should be removed at 36 weeks, and thereafter the patient can be referred to antenatal services at primary level of care.
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REFERRAL
Women with recurrent losses and previous cerclage that tore out (severe cervical trauma), as they may require an abdominal cerclage.
Standard Treatment Guidelines and Essential Medicines List for South Africa, Adult Hospital Level, 2025-9 Review_Version 2.0_26 March 2026
Chapter 6 Obstetrics_6.11.2 Prevention of Preterm Labour