Cervical Length Measurement During Pregnancy: What to Expect

Question
I am 26 weeks pregnant and my outer cervix for some reason is opened slightly. My obgyn wants to do an ultrasound to determined cervical length. Is this procedure done just like previous ultrasound when they detected the sex of the baby? If not, how is it done?

Answer
An obstetrical ultrasound is done the same way at all times. The cervix should be at least 3-4cm in length. If it is shortening or "funneling" it may be a sign of preterm labor. Until you get the sonogram, refrain from sexual intercourse, heavy lifting, or straining. Very often, we find the "external" cervix slightly open while the "internal" cervix is completely closed. Don't worry.  If the cervix is at least 3-4cm in length, there is nothing to worry about.