cervical lengths??

Just wondering some things for those who have experience with having cervical lengths measured.
So, since DD was born at 26 weeks, we're checking cervical lengths every 2 weeks this pregnancy. We stared at 18 weeks. At 18 & 20 weeks, my cervix was 4.1.-4.4 cm which we were very happy with I wasn't scheduled to go in until next week at 22 weeks, but I went in today because I've been freaking out & driving myself crazy here at home while on bedrest (due to placenta placement). I keep thinking I'm contracting, but not 100% sure, have had a backache & achy in my perineum area.
So I went in, no contractions after 30 minutes on the monitor Did another cervical length & I'm not sure if the U/S tech took more than one measurement like they usually do, but she said I was at 3.9 cm. She also took a measurement as I was bearing down & that was 3.5 cm.
My usual OB was out of the office & the nurse said since everything looked OK, I didn't need to see anyone else, but did get a phone call from one of the other OB's to follow up after I got home. She said they recorded my cervical length at 3.5 cm & they were still happy with that.
I'm just wondering how much others have seen in variation from check to check. I was wishing to still be > 4 cm at this point so I'm a bit disappointed, but wondering if it's normal to have variation like this - maybe I'll be >4 at the check next week?
Do you think it's normal to have the cervix shorten like it did for me when bearing down - I think of every time I cough or have a BM that my cervix is shortening
I will have another check next week at 22 weeks & will get to see my usual OB so hopefully will get some more answers then.

The only reference point I have is from Keepemcookin.com:

* At 16 to 20 weeks, normal cervical length is 4.0 to 4.5 cm
* At 24 to 28 weeks, normal cervical length is 3.5 to 4.0 cm
* At 32 to 36 weeks, normal cervical length is 3.0 to 3.5 cm

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Even i want to know
I had 4.2 cm at 16 weeks and 4.2 at 20 weeks and on last u/s at 24 weeks it was 4 cm.
Now they dont want to check again. As they said you dont need to check it again.

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I'm glad that you started this because, even though I had my baby at 28 weeks I still don't understand what exactly it means. At 28 weeks I went in for the glucose test at about 10 am. My cervix was still "thick" according to the dr., and I guess this meant length. Later that day I started to feel som regular pressure. I called the OB at about 9:00, went to the hospital, and my cervix was now at 0.2 cm. How does it change so fast? Do contractions cause the length to lessen, or does the cervix shortening cause the contractions? (that might sound silly, but they seemed to have happened at the same time).

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This is one other thing from keepemcookin.com....
"Cervical length at approximately 24 weeks into a pregnancy is an excellent indicator if not the best indicator of a pregnant woman's risk of preterm birth. The length of the cervix is most accurately measured by transvaginal ultrasound, which your doctor may not consider doing unless you specifically request it. Normal cervical length is 4 to 5 cm.

One study found that at 24 weeks gestation, the average cervical length is 3.5 cm. When cervical length is less than 2.2 cm, women face a 20 percent probability of preterm delivery. (Source: The Length of the Cervix and the Risk of Spontaneous Premature Delivery. New England Journal of Medicine; February 29, 1996; Vol. 334, Number 9: 567-572.)

Another study found that when the cervical length measures 1.5 cm or less, the risk of spontaneous preterm birth is almost 50 percent. (Source: American Journal of Obstetrics and Gynecology; June 2000; Volume 182 6 :1458-1467) "

According to this, Fozia, this would indicate that you should be OK, but I can see where you're nervous too.

But the article doesn't really let you know if the cervical length can vary shorter/longer from week to week?

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For me, my cervix shortened fairly quickly. I vaguely remember, but I believe at 22 weeks my cervix measured 3.3, then at 25 weeks 6 days, it was 2.7cm and soft, and I delivered the two days later. Looking back at my records, my cervix did fluctuate a little, would go from 3.4 to 3.7, and I didn't realize that could happen. Although I wonder if it was just error by the sono tech. At the 24 week cervical length check, my OB said I didn't need anymore and she was not concerned. Although, I believe she based her decisions on the statistics, that it was probably not going to be a problem. Since the birth of my son, I have seen 2 high risk OBs and neither seem to think my cervix was incompetant. So I still dont' know and might never know why my son was born so early. If you are really concerned and it's causing anxiety, I would ask for weekly checks for peace of mind until you get to a point where you aren't stressing about it. Seems cervical lengths can change very quickly, without warning! Good Luck and keep us posted.

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