Risk of Preterm Birth by Cervical Length – Sunnybrook Data

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A short uterine cervix (as measured using transvaginal ultrasound) is one of the strongest
predictors of preterm birth in twin pregnancies, but the meaning of a given measurement depends on
when in pregnancy it was obtained. Use this calculator to estimate the risk of spontaneous preterm
birth in twin pregnancies (expressed in %) based on the length of the uterine cervix (in mm) and the
gestational age at which this measurement was obtained. This calculator is based on 1,752 twin pregnancies followed at the Sunnybrook Twins
Clinic – see original publication:
[link to be added on publication]

Gestational age at measurement of cervical length

16–29

0–6

Cervical length

0–70

Disclaimer

The information, content, and tools contained on this page are for information
purposes only. They are not intended to be a definitive means of assessing the probability of any
pregnancy, fetal, or infant outcome, and are not intended to be a substitute for professional
advice, diagnosis, or treatment. The content provided here should not be the sole basis for making
decisions regarding an individual’s healthcare. Users viewing these resources should always seek the
advice of a physician or other qualified health provider with any questions they may have regarding
a physical and/or psychological condition. The information and tools contained on this page are
intended for personal use only, and may not be used in any commercial manner. Sunnybrook hereby
disclaims any, and all, liability to any party for any direct, indirect, implied, punitive, special,
incidental, or other consequential damages arising directly or indirectly from any use of the
content on this page. The information, content, and tools contained on this page are provided as is,
and without any warranties or guarantees.

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calculators*

Risk of spontaneous preterm birth
Spontaneous preterm birth Estimated risk
Before 34+0 weeks —
Before 32+0 weeks —
Before 28+0 weeks —

Spontaneous preterm birth means birth following spontaneous onset of labour or
spontaneous rupture of membranes. Births for which delivery was initiated for a medical
indication are not included. For reference, the overall rates in this cohort were 13.8% before
34 weeks, 8.0% before 32 weeks and 3.0% before 28 weeks.

Estimated risk across the range of cervical length