What is the normal range for the length of the cervical os in centimeters?

What is the normal range for the length of the cervical os in centimeters?

• A. 2.0-3.0
• B. 2.5-4.0
• C. 3.0-5.0
• D. 4.0-6.0

Answer: (B)

The measured length of the cervical canal (from internal os to external os) is normally about 2.5 to 4.0 cm. This range is used because it reflects typical anatomy in a healthy cervix, and measurements shorter than about 2.5 cm are considered shortened and can be associated with a higher risk of cervical insufficiency, especially in pregnancy. Measurements within 2.5–4.0 cm are regarded as normal variations for nonpathologic cervical length, usually assessed by transvaginal ultrasound for accuracy. The other ranges either underestimate or overestimate the typical canal length and do not align with standard normal values.

The measured length of the cervical canal (from internal os to external os) is normally about 2.5 to 4.0 cm. This range is used because it reflects typical anatomy in a healthy cervix, and measurements shorter than about 2.5 cm are considered shortened and can be associated with a higher risk of cervical insufficiency, especially in pregnancy. Measurements within 2.5–4.0 cm are regarded as normal variations for nonpathologic cervical length, usually assessed by transvaginal ultrasound for accuracy. The other ranges either underestimate or overestimate the typical canal length and do not align with standard normal values.