The gentlebirth.org website is provided courtesy of
Ronnie Falcao, LM MS, a homebirth midwife in Mountain View, CA

Bicornuate Uterus

There are a number of ways that a uterus can be shaped differently from "normal". The most common is the bicornuate uterus, which means the uterus has two horns. These are caused by something that goes wrong in the normal development of the open uterine cavity from the two tubes; typically the tubes separate incompletely somewhere along the line. Sometimes this results in a nice heart-shaped uterus which has little effect - sometimes the two sides are separated all the way down the middle, which is kind of a birthing challenge and may result in a higher incidence of miscarriages as the placenta may develop on the septum, which has an inadequate blood supply. Many cases of bicornuate uterus are somewhere in between.

Babies normally turn head down because there's more room in the top of the uterus to accommodate the baby's hindquarters. However, with a bicornuate uterus, the baby may fit better with the head up top and the hindquarters lower in the pelvis. So there's a higher incidence of breech positions with a bicornuate uterus, but the baby may also turn head down. It may depend on the exact shape of her uterus, the baby's size, the phase of the moon. It's not true that every woman with a bicornuate uterus will carry a breech baby. In fact, the first birth I ever attended (as a friend) was a VBAC in a woman with a bicornuate uterus whose first baby was breech and whose second was not.

Based on statistics only, and knowing nothing about this individual woman and her baby, a bicornuate uterus is more likely to have a placenta that degrades before term, which can compromise the baby's health. Some OB's will recommend doing a cesarean at 37 weeks or some weeks before term. Rupturing membranes and any subsequent contractions cause a release of hormones that helps the baby's lungs to mature. Knowing they were going to be delivering a baby three weeks before term, it seems responsible to do this, although I'm shocked they actually sent the woman home instead of keeping her in the hospital after rupturing membranes.

An alternative way of dealing with the concern about a degrading placenta in a bicornuate uterus is to keep a close eye on kick charts and maybe, oh, this is so seditious, maybe teach the woman and her partner how to listen to the baby's heart rate so they can listen once or twice a day to look for patterns that might warrant further investigation.

And, of course, an alternative to cesarean for breech is a vaginal breech delivery.

I am preparing a teaching topic for work - I am a registrar in O&G in London. I was interested in your page about bicornuate uterus, but would take issue with several points. The most common form of uterine abnormality is not bicornuate uterus (uterus didelphys) but rather, I would think, a simple septated or subseptated cavity. This is not formed by incomplete separation of "the tubes" in development, but rather the opposite, a failure of fusion in the midline of the two halves of the Mullerian ducts. In the worst case there may be two uteri, two cervices, and two vaginas. The major problems associated with bicornuate uterus are malpresentations of all kinds, and premature labour, although if you are delivering after 37 weeks there is not too much to worry about, I would suggest, with regard to the fetal lung maturity.