The fallopian tubes, uterus, cervix, and upper vagina begin development as two parallel tubular structures - these are the mullerian ducts. During embryonic development, the lower part of these structures grow together - this process is called fusion. Then the parts that are fused together disappear to form a single (larger) tubular structure - this process is called resorption. The fused (and partially resorbed) part of the mullerian ducts becomes the uterus, cervix, and upper vagina. The (unfused) upper part becomes the fallopian tubes. The diagram at left shows a cross-section of a normal uterus.
When this embryonic process goes awry, a number of different genital birth defects can occur. If there is no fusion, two separate uteri result (this is called uterus didelphys). The will be two separate cervices, and sometimes two vaginas. If fusion occurs only at the very bottom of the ducts, you get a bicornuate ("two horned") uterus. The diagram at left is a cross-section of a bicornuate uterus. Note that the upper part of the uterus consists of two distinct structures separated by a cleft. Women with a bicornuate uterus are at an increased of (late) miscarriage, preterm birth, and abnormal fetal lie (usually breech). Although there is a surgical procedure described to fix a bicornuate uterus, it is no longer recommended by experts in the field, because: (1) the pregnancy outcomes are quite good if you just stitch up the cervix in the next pregnancy, and (2) it's a fairly drastic operation, involving cutting the uterus open and sewing it back together.
If fusion occurs but resorption is incomplete, you get a septate uterus. Here is the diagram of a septate uterus. In the middle of the uterine cavity is a fibrous, avascular partition (the septum). Note that from the outside, the top of the uterus appears normal. (It's generally a bit wider than normal, but the top has no cleft just like a normal uterus.) Women with a uterine septum have twice the risk of miscarriage as other women, and they are more likely to have problems with preterm delivery and breech birth, too. The treatment for a uterine septum is to just cut the septum with scissors, and this can be done as an outpatient.Generally, a woman finds out she has a bicornuate or septate uterus when she gets a hysterosalpingogram for infertility or recurrent miscarriages.
Here are some normal uterine cavities on HSG:
Note that the uterus in the lower photo has a bit of a curve in the top of the cavity. This is a normal variant.
Now take a look at these HSGs:
There is an obvious cleft in the uterine cavity. This HSGs are commonly read as "bicornuate uterus" by some physicians, but in reality it could be a septate uterus or a bicornuate uterus. Let me state this again: YOU CANNOT DISTINGUISH A SEPTATE UTERUS FROM A BICORNUATE UTERUS WITH A HYSTEROSALPINGOGRAM. Yes, I know there was a paper published years ago which said you could distinguish them by measuring the angle between the cavities, but it just ain't so. The two tests which can best distinguish a septate from a bicornuate uterus are a transvaginal ultrasound and a pelvic MRI.
Now, the sad thing is that one of my recent patients actually had an MRI, and the diagnosis was still missed. It turns out that not all radiologists understand the difference between a septate and a bicornuate uterus. They often just put "uterine duplication" in the MRI report, and that's what probably happened with my patient.
The next post will show how to distinguish a septate uterus from a bicornuate uterus using transvaginal sonography.
16 comments:
Funny I was looking for your phone number to refer a patient with, alas, a thick uterine septum and ran across this blog. I discovered this finding with hysteroscopy and laparoscopy. Interestingly you do not mention endoscopy in your review of diagnostic modalities. I realize this is an aggressive tact to ascertain this diagnosis,a tact the blue bean counters would probably frown upon (and for the record the patient has long standing pelvic pain and we found endometriosis at the time of her surgery; just in case said bean counters are watching)
and at tact I will blame my heady formative years at the mecca for such thinking!
I appreciate the comment from one of my former students, whose dry wit seems to have survived the rigors of medical training and practice. Of course, you are correct that the two conditions can be differentiated at laparoscopy/hysteroscopy.
MPS
What is the advantage/adaptive significance to having a simplex uterus in humans as opposed to a duplex uterus in rabbits?
My guess is that primates evolved a "simplex" uterus to facilitate the development of a large singleton infant. Mammals such as cats and rabbits, where multiple pregnancy is the norm, have a bicornuate uterus (and more than two breasts). A bicornuate uterus has a greater surface area for a given volume, which probably facilitates multiple implantations. Now, there are some large animals (elephants, horses, cows) who typically deliver singletons and have bicornuate uteri, but their newborns represent a smaller percentage of adult body weight than human infants.
I was diagnosed with a septate uterus in 2002 when the doctors did a trans vaginal ultrasound.
I was re-diagnosed This past October when the doctor did an HSG with a bicornuate/ possibly a unicornuate uterus. The doctor wanted to a procedure to go in and look with a camera to see however I had become pregnant! After 7 years of trying we finally got pregnant.
However during the 7th month of my pregnancy ( 28 weeks 5 days) my daughter died of unknown causes.
They are going to do an MRI next Wednesday on my uterus to see if they can tell if it is a true bicornuate. After my loss, I had to have a D&C after almost bleeding to death and they said I had 2 cavities.
I was just wanting to know your knowledge about pregnancy and bicornuate/ septate uterus. Do a lot of people lose babies because of the uterus? I was told that I had nothing to worry about and that I was only high risk for premature delivery. I don't know many people with Bicornuate uterus and apparently the doctors in the practice I go to don't know much about it either which makes me nervous about trying to conceive again.
Do you know any problems with pregnancy that result in the symptoms: Back cramps followed by a little bright red blood, a week later having severe headache lasting more than a day, and seeing white floaty spots (like a disco ball being held up to the sun?) And than more headaches?
In your knowledge, can the testing they do for pregnancy diabetes kill a baby?
My daughter died a day after I had an ultrasound saying she was fine, and that same day we had done the diabetes testing.
I understand you won't know the answers to these questions, I just have a little hope that you might know what caused this to happen. I just want to know if it is common for women to lose their babies in the third trimester just because they have a bicornuate uterus/ sepate uterus? Is it possible that my uterus caused my daughters death?
Does a uterine septum cause stillbirth? If you look around in the medical literature, you can find references that note stillbirth is less likely after resection of a uterine septum, but the problem with this sort of study is that women with adverse reproductive history are more likely to have a uterine septum identified (because women with normal birth outcomes don't get an HSG), and a stillbirth is unlikely to recur in a given patient, even if no treatment is done.
I think that if you have a uterine septum, it should be cut. The fact that your doctors are ordering an MRI to figure out whether you have a septum or a bicornuate uterus suggests that either there is something about your case that you haven't mentioned, or (more likely) your doctors don't have much experience in managing this condition. I suggest you seek a second opinion. mps
Michael, thank you for this post as it is some of the clearest information I've been able to find on the subject!
In reference to the paragraph:
Although there is a surgical procedure described to fix a bicornuate uterus, it is no longer recommended by experts in the field, because: (1) the pregnancy outcomes are quite good if you just stitch up the cervix in the next pregnancy, and (2) it's a fairly drastic operation, involving cutting the uterus open and sewing it back together.
Can you further explain how the cervix might be stitched in the case of a bicornuate uterus? How difficult of procedure is it?
Thanks so much.
Michael, does Alabama Fertility perform the surgery if necessary?
See here for more info about cervical cerclage: http://en.wikipedia.org/wiki/Cervical_cerclage.
We don't usually do them at AFS because most of the cerclages are performed by obstetricians after 12 weeks of pregnancy. I wouldn't hesitate to do a laparoscopic cerclage before pregnancy, though.
mps
After my first ultrasound during a pregnancy back in March I was told that I either have a bicornuate or septate uterus but they couldn't tell which. I have since miscarried that pregnancy and one other since then. I also believe I had a miscarriage back in July of 2008 which was never diagnosed(my doctor just treated me for a heavy period with birth control pills). I'm terrified of getting pregnant again and my current doctor does not seem interested in doing any testing to see what the situation really is. Is this a case for an RE or should I just pressure my OB for answers?
Come see me!
mps
Good doc removed my septum in 2008!
Can having a bicornuate uterus or septate uterus cause long and heavy cycles longer then 3weeks. I was recently diagnosed. Looking for further information. My appt with my GYN isn't till next week. Thanks
No, to my knowledge those anomalies don't cause long, heavy periods.
thanks a lot !!
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