The Mullerian Inheritance

At about eight weeks of pregnancy (eight weeks from the last menstrual period, or LMP) the kidneys begin to develop in the fetus. For females, the ovaries then take shape just below them; for males, the testes form there. At this early time,the embryo's head has taken shape, and the heart is prominently responsible for the growing circulation. The tail end of the embryo, however, is still rudimentary and rather plastic--able to end up in all sorts of directions. In females, an open duct the MuIlerian duct begins to form near each ovary, as the tail end of the embryo takes more shape passing over toward the middle. Here it will meet its companion duct from the other side, join, and then grow further downward, opening into a space formed as a pocket from the skin between the embryo's leg buds; this will later be distinguishable, from front to back, as the urethra, vagina and anus. Where these two Mullerian ducts join, they thicken considerably to form the uterus; the parts of the ducts on each side of the joining become the fallopian tubes. The joined part of the Mullerian duct forms, from top to bottom, the body of the uterus (the uterine fundus), the neck of the uterus (the cervix) and the upper two-thirds of the vagina. The lowermost part of the vagina comes from the skin.

Congenital Anomalies

Congenital means something you are born with. If something can go wrong in the way the body is put together, sooner or later it will, and a baby will be born with an anomaly, or a variation from what is normal. The kidney system is close enough to the developing genital system that anomalies of the two systems often go together. For the Mullerian ducts and the internal sex organs, things may go wrong symmetrically, in which case the kidneys are usually normal; or things may be lopsided, or asymmetrical, in which case commonly there will be a malformation of the kidney system on the abnormal side.

Unicornuate Uterus

With a unicornuate uterus there is one uterus and cervix and usually one vagina (all normal-looking so far). On investigation, however, with a hysrterosalpingogram or Iaparoscopy (usually done for other reasons), only one fallopian tube is found to be open. Development of the fallopian tube on the other side can be variable; the outer, open part is usually there, lying next to the ovary, but toward the middle it either dwindles into nothing, or it expands to a more or less distinct uterus, partly joined onto the main uterus. Usually there are no symptoms, but, if the rudimentary uterus (or "horn) is unrudimentary enough to have a cavity, pain can be felt on that side during periods; sometimes this is bad enough to warrant an operation for its removal. On average, a woman will take twice as long as otherwise to get pregnant, because conception is very unlikely when ovulation takes place on the closed side. Premature births and breech births are more common, as they are with the bicornuate uterus . Occasionally a pregnancy will start in the closed side. When this happens it will be because sperm have passed up the open uterus, out along its tube and across the abdomen to the opposite ovary, fertilizing an egg just as it is being picked up by a fallopian tube that leads nowhere. The result is a pregnancy in the tube or in the rudimentary uterus, in effect an ectopic pregnancy and sooner or later a surgical emergency.