Senior Consultant, Fetal Medicine, Artemis Hospitals, Gurgaon, India
Part 6 of 7 in Diagnostic Utility of First Trimester Ultrasound
Predicting Preterm Labour: Why Cervical Length Should Be Measured at 12 Weeks
June 21, 2026
The first trimester scan can also predict preterm labour risk, and Dr. Sablok stresses that cervical length measurement doesn't need to wait for the later anomaly scan: it can and should be done as early as 11-14 weeks. She describes patients who came in for a routine anomaly scan with cervical lengths of just 16mm and 18mm, putting them at very high risk of preterm labour that had gone undetected until that point.
The earlier a short cervix is caught, the earlier progesterone can be started, or, if the cervix is very short, or there's a history of recurrent miscarriage or preterm labour, a cervical cerclage placed, reducing the risk of preterm birth. All these parameters feed into a calculator estimating the risk of spontaneous delivery before 34 weeks, with vaginal progesterone and cerclage as the main management options.
This guide is based on a live Jivo Masterclass — Dr. Aanchal Sablok taught doctors across Africa on June 21, 2026.
FROM THE LIVE Q&A
How does the stage of CKD (chronic kidney disease) affect the risk of preeclampsia?
Dr. Aanchal Sablok
If the mother already has chronic kidney disease, she is already at risk of chronic hypertension. When placental implantation occurs on top of this background, the relevant terminology is preeclampsia superimposed on chronic hypertension. This represents an even higher risk of developing preeclampsia, particularly in the presence of chronic renal disease, chronic hypertension, or other conditions such as autoimmune disease. The risk of fetal growth restriction (small for gestational age) is also correspondingly higher in this group.
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Frequently Asked Questions
When should cervical length first be measured in pregnancy?▼
Cervical length measurement does not need to wait for the later anomaly scan. It can and should be done as early as 11 to 14 weeks.
What cervical length findings signal a high risk of preterm labour?▼
Cervical lengths of just 16mm and 18mm, found in patients who had come in for a routine anomaly scan, put those pregnancies at very high risk of preterm labour that had gone undetected until that point.
What can be done once a short cervix is identified early?▼
The earlier a short cervix is caught, the earlier progesterone can be started. If the cervix is very short, or there is a history of recurrent miscarriage or preterm labour, a cervical cerclage can be placed, reducing the risk of preterm birth.
What does the preterm labour risk calculator estimate?▼
It estimates the risk of spontaneous delivery before 34 weeks, with vaginal progesterone and cerclage as the main management options for pregnancies found to be at risk.
In This Series: Diagnostic Utility of First Trimester Ultrasound
- 1.Diagnostic Utility of First Trimester Ultrasound
- 2.Screening for Down Syndrome: How Detection Rates Evolved From 30% to 96%
- 3.Nuchal Translucency: Why a High Reading Doesn't Mean What Patients Fear
- 4.Structural Abnormalities the First-Trimester Scan Can Already Catch
- 5.Preeclampsia Screening: Uterine Artery Doppler, PLGF, and the New Role of the Ophthalmic Artery
- 6.Predicting Preterm Labour: Why Cervical Length Should Be Measured at 12 Weeks
- 7.The Inverted Pyramid of Care: Rethinking When Pregnant Women Should Be Seen