An American woman with a double uterus, a rare condition that affects around 1 per thousand women in the US, is expecting two babies, due one week apart, but they are not twins because one baby is growing in one womb and the other baby, conceived at a separate time, is growing in the other womb.

A CBS Atlanta report last week said that Angie Cromar, a labor and delivery nurse from Utah, told them her husband wouldn’t believe her at first when she broke the news to him.

Cromar has a rare condition called uterus didelphys. It develops in the female fetus before birth and occurs when two tubes that normally fuse together to form the uterus fail to do so, developing into two separate cavities, sometimes each with its own cervix. In some cases, the woman can also have a duplicate or divided vagina.

Cromar knew before she was pregnant with her current two babies that she had the condition, but as she told CBS Atlanta it had not been an issue in her other pregnancies. She said she already knew about the possibility that her babies could be premature and have low birthweight.

There have only been about 100 cases worldwide of a woman with a double uterus being pregnant in both wombs at the same time.

Double uterus is sometimes not even diagnosed: some women don’t even realize they have one, even during pregnancy and childbirth. Symptoms include unusual pain before or during a period and abnormal bleeding during a period.

According to information from the Mayo Clinic, treatment is only necessary if there are symptoms or complications, such as repeated miscarriages or pelvic pain.

Many women with a double uterus have normal pregnancies and deliveries, but sometimes they can experience infertility or miscarriage, and the risk of pregnancy complication could be higher because the wombs are slightly smaller.

Premature birth can occur if the baby is in an unusual postion, such as in breech (bottom toward the birth canal).

According to New York Daily News, Cromer said in an interview with local tv station KSL that she was “a little nervous”, because she knew what might happen:

“But I’m really excited,” she said.

Sources: CBS Atlanta, Mayo Clinic, Medscape, New York Daily News.

Written by: Catharine Paddock, PhD