MOMS-TO-BE: What You Should Know About Cervical Length

February 27th, 2013

by Elizabeth T. Jordan, DNSc, RNC
Johns Hopkins School of Nursing


As an expectant mom, your prenatal care provider may advise you to have an ultrasound scan to measure the length of your cervix. Your cervix is where your uterus, also known as your womb, opens into the vagina. Women with a short cervix in the mid-trimester may be at increased risk for preterm delivery.  Several studies have shown that women with shorter cervical length, as measured by an ultrasound, are at higher risk for having a preterm birth.

Your cervical length can be measured by a transabdominal ultrasound, and/ or a transvaginal ultrasound. CerviLenz is a disposable device, that looks like a long cotton swab, that also measures cervical length and can be used by the provider during an examination in the office or clinic. The transvaginal scan is currently thought to be the best way to measure the cervix because it can be seen much more clearly this way.

The cervix should be between 3 cm and 5 cm long, with one end at the top of the vagina (the external os) and the other end inside the uterus (the internal os). If the cervix measures less than 2.5 cm, your health care provider may request you have additional scans and recommend further treatment based on your obstetrical history. The care provider may also look at the shape of the cervix and watch to see if the cervix changes from V-shaped to U-shaped. This is called “funneling” of the cervix.  If you cervix is short (<2.5 cm) and shows funneling, it puts you at a higher risk for delivering your baby early. Your provider may recommend additional treatment.

Your cervical length measurement may also be calculated when an ultrasound is being performed to confirm your due date and look at the growth of your baby. Routine ultrasounds are usually done between 19-24 weeks’ gestation.

Your cervix should remain closed throughout pregnancy until just before birth.  If the cervix begins to open before you are full-term, this may be a danger sign and may place you at risk for infection or premature dilation. The cervix has a mucous plug, also known as show, and, it protects your womb. Cervical length measurement is recommended if you are expecting twins or have had surgery to your cervix.

Cervical length is currently not routinely being performed on every pregnant woman. However, results from several studies build a strong case that pregnant women with a short cervical length are at higher risk for delivering preterm.  Knowing if you are at risk for preterm birth can help guide your prenatal care and minimize your risks.


37 Responses to “MOMS-TO-BE: What You Should Know About Cervical Length

  1. Alexia says:

    A cervical length check during pregnancy should be mandatory.

  2. Alexis says:

    NOTHING should ever under any circumstances be mandatory!!! A doctor can give strong recommendations but should never have the ability to force you to do something.

  3. Alexandria says:

    I think this should be done at every doctor office! I had NO indication that I had an incompetent cervix. Two days prior to having to leave out of state for 2 weeks, my doctor performed a cervical check as part of the standard growth check. It turned out it was 2.1 inches and I was funneling. This would have turned into a nightmare if it progressed since I was only at 20 weeks and could have lost the baby- all in another state too! I was prohibited from attending the event and received treatment instead. Now things are looking up and the baby is still alive, all because they had the fortitude to check the length of my cervix. They didn’t ask me, they just made sure it was part of my visit.

  4. Reema M says:

    At 18 week with 3.8 cervical lenght. Does it need cervix stitch. And after stitch can we start our routin house work.

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  6. raj says:

    i am at 8 th week of my pregnency and it is early pregnency.i have cough and headache light this causes any harm to my baby.plz give me reply.

  7. admin says:

    Please talk with your healthcare provider about your symptoms, to ensure that you get personalized medical advice and care. We wish you a healthy pregnancy!

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  14. funtreasure says:

    Please i want to ask what the cervical canal should measure before pregnacy. An hsg report measures 18mm, what is the implication of this?
    Response urgently needed via my mailbox provided.
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  15. Second_time_mom says:

    I am currently 22 weeks with a CL of 2 cms and no such history in my last pregnancy. My first baby was born in June 2013 and I conceived again in July 2014. Rather my cervix didnt dilate in the last pregnancy. I am living in Gulf and absolutely no help at home. no baby sitter nothing. I want to go back to my Mother. but the flight will take 6 hours. can i take a flight with this situation. Kindly reply

  16. Amanda says:

    I’m on pregnancy 9 (most have been chemicals but 3 later losses). In my last pregnancy my MFM checked my cervix EVERY time I went (every 2 weeks or more) and it was always fine. I had a D&C (only one) between that pregnancy and this so know things can change. At 15w I had labor like pain and went to the ER. They manually checked my cervix ONLY and told me it was “closed”. I expressed concern they weren’t checking length or for funneling and was told they don’t do that. I went to my OB after and he felt with his fingers and told me my cervix was “long”. No U/S or swab as described above. Can they check length that way?

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  18. Indumini says:

    I’m 32 years of age & looking for baby during last 4 years. I had sub fertile drugs from my VOG & got pregnant in 2013 & it was ectopic & done laparotomy. Then again I was pregnant in 2013 October & had a preterm birth in March 2014, in 19 weeks & again I lost my baby.My cervical length was 4cm. Then I pregnant in 3rd time on October 2014, my doctor decided to put Cervical Cerclarge. The cerclarge was put when 14 weeks, but unfortunately again had a preterm birth in 18 weeks & again I lost everything. Is the only way to prevent my baby, putting cerclarge. Is there any reason for happening this again & again. Please reply me.

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  20. safa says:

    dear indumini i am so sorry to hear about ur losts….i knew som1 who keept losing her babies but finally she had i.think 2 boys and 1 girl so don’t worry i pray for u from God Almighty that u will have one soon☺ just pray as.much as u can as only God has unlimited power. Ameen

  21. Jamilah says:

    Dear Indumini, Im sorrry for your losses. I understand what youve been through. I have had two 2nd trimester losses, one at 19 weeks due to my cervix being too weak (incompetent cervix) which I had no clue of until ut was too late. My second pregnancy I got a Mcdonald cerclage placed at 13 weeks which still did not prevent my cervix from dilating early. At 23 weeks my water broke and I misscaarried days later. I had high hopes for the Mcdonald cerclage and when it failed I learned of an alternative cerclage called transabdominal cerclage. Its placed at the highest point of your cervix through an incision similar to c section through the stomach. I had mine placed a week ago at 12 weeks and it went well. Im home now and healing wonderfully. My first post op ultrasound is tomorrow for then to check the stitch and measure my cervical length. Every couple weeks I will have to get checked but I have a piece of mind knowing there is a 90% success rate with the TAC. Now im just being prayerful that the stitch holds up until Im at least 37 weeks. Very few doctors perform the TAC but if I were tou I would travel to get it if I couldnt find one in my vacinity. Good luck with everything and I hope this was helpful. If you have any questions feel free to ask.

  22. sruthi says:

    Hi sir, i got my scanning done today and my baby is 7 weeks now.. The cervix length was observed to be 2.8 cm… doctor told me to take rest.. Is there something serious.. Please reply..

    Thanks in advance

  23. Heena says:

    i had premature child birth in last 2 yrs one in 4 months and second in 6 month bcoz of shortening of cervical length. pls suggest its cure…

  24. daniya says:

    Hello My cervix length is 4.2 cm and I am 22 weeks pregnant. So, do I have chances of vbac.

  25. September/October bump buddies anyone wlecome! - Page 50 - BabyandBump says:

    […] JandJ your lo is so precious! So I was curious as to how long your cervix is suppose to be as I've never really thought about it and according to what I read it should be between 3 and 5 cm. So from that I was think your cervix length is in the normal range. Keep us updated as to what the doctor says tomorrow. Here is the link I found this information on. […]

  26. anila says:

    my crovical lengh is 2.9 cm and iam 24 weeks pregnant so do have chance

  27. anila says:

    please answee me iam very absat

  28. marree says:

    I m 21 week pregnant n my cervical length is 3 cm n my baby head iz low ..plz tel me wt should I do
    .iz it dAngerous

  29. Mrs Aamir says:

    I am 23 weeks pregnant my cervical length is 3.6 cm nw but i had a history of short cervical length and had a cercalage in my 1st baby .is there any danger or risk of shortening in 23 weeks??

  30. Mrs Aamir says:

    anila u must take care bcs its below 3 cm

  31. suganthi s says:

    now i am in concieve at 8 weeks, my cervical measure in 2.6 cm length. any problem for this length.

  32. Purva says:

    I am 14 weeks pregnant(1st time) my cervical length is 2.7 cm any problem for this length?

  33. Jessica says:

    21 weeks cervical measurement 2.2. One week ago it measured 2.7. I delivered a son 7 months ago at 32 weeks and he is healthy but I conceived within 3 months and am now terribly worried. I’ve been prescribed progesterone suppositories and will head to Boston again in a week and if it continues to shorten I will have a cerclage placed in. Please any advice? I cannot breat much as I have my 7 month old to care for and my husband works two jobs so that I don’t have to work. I’m so scared

  34. KG says:

    I lost my twin girls 23+ weeks and i am currently expecting. i was told to do a scan at 12 weeks 2 days and my cervix is 3.43 so i need to do a cerclarge since i lost the twins earlier this year.

  35. Mafia says:

    i have pregnency of 22 weeks and today my cervical length is measured 3.1 cm in ultrasound. i want to know is it dangerous or not??

  36. pinkii says:

    my cervical length is 2.9 at 13 it a serious issue? i hv to go thru surgical sticthes process ?

  37. aarti says:

    my cervical length is 2.7 at 8 weeks 6 it a serious issue? i hv to go thru surgical stitches process ?
    what precautions to be taken? Dr. has given me a injection and advised me to take it on weekly basis for 4 wks. Is it help?

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