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Do You Know How Long Yours Is?
My patient was 22 years old and midway through her first pregnancy when she arrived for an ultrasound examination. It was a routine evaluation in every way, and in the darkened room, the ultrasound technologist moved the ultrasound probe over the patient's gel-covered abdomen, cataloguing a long list of normal fetal structures.
Then the tech did something incredibly important: she aimed her ultrasound probe toward the patient's cervix.
"I think the cervix is short," she told me.
It can be difficult to measure the cervix using the same external ultrasound probe that is used to examine the fetal spine, heart, and other anatomic structures. The cervix can easily become lost among the other pelvic organs that look similar on ultrasound.
"Let's do a vaginal ultrasound," I suggested. This approach allows for reasonably easy measurement of the cervical length.
On the grainy, black-and-white screen, the cervix in cross-section appeared like two loaves of bread placed bottom to bottom. The tech was correct. My patient's cervix was only 1.8 cm long, well below the 3 cm threshold we use to define normal.
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