Depending on the shape of the uterus, the risks of miscarriage or premature birth can be higher in these cases. Uterine abnormality is also linked to cervical insufficiency/incompetence, another factor leading to preterm birth.
Bicornuate (heart-shaped) womb
A bicornuate womb is heart-shaped. Women with a bicornuate womb have no extra difficulties with conception or in early pregnancy, but there is a slightly higher risk of miscarriage and preterm birth. It can also affect the way the baby lies in later pregnancy so a caesarean birth might be recommended.
Having a unicornuate womb is rare. It means your womb is half the size of a normal womb because one side failed to develop. There is an increased risk of ectopic pregnancy, late miscarriage or preterm birth. The baby may lie in an awkward position in later pregnancy so a caesarean birth might be recommended. Women with a unicornate womb can often conceive, although it is also true to say that the prevalence of unicornuate uterus is higher in women who are infertile.
Didelphic (double) womb
The didelphic womb is split in two, with each side having its own cavity. Generally the duplication affects uterus and cervix but it can also affect the vulva, bladder, urethra and vagina. Women with a didelphic womb have no extra difficulties with conception and it is only linked to a small increased risk in premature birth.
The septate womb has a wall of muscle coming down the centre splitting the space in two. Sometimes the wall only comes part-way down the womb (subseptate) and other times it comes the whole way down. Women with subseptate or septate wombs are more likely to have difficulties with conception. There is also an increased risk of ﬁrst-trimester miscarriage and preterm birth. In later pregnancy the baby may lie in an awkward position.
The arcuate womb looks very like a normal womb but it has a dip at the top. Arcuate womb does not increase your risk of preterm birth or first trimester miscarriage but it does increase your risk of second trimester miscarriage. In later pregnancy your baby may lie in an awkward position so you may need to have a caesarean birth.
How will I know if I have abnormal womb?
There are unlikely to be any physical symptoms in early pregnancy.
If you have a didelphic (double) womb or a unicornuate womb it may be spotted in your routine scans as it looks very different from a normal womb. In other cases, especially if the abnormality is not severe, it is unlikely to be picked up as routine pregnancy scans do not specifically look for this.
Most women are unaware that they may have an abnormal shaped womb when they become pregnant however some may already know as they have had investigations following recurrent first-trimester miscarriages (three or more), a gynaecological problem such as experiencing symptoms of abnormal bleeding including very heavy periods or bleeding between periods.
One of the following investigations will be offered: a hysteroscopy, a laparoscopy or a three-dimensional pelvic ultrasound scan.
The hysteroscopy involves a small camera being sent through the cervix in to the cavity of the womb. In order to do this a fluid is introduced to increase the cavity of the womb order to gain a better view. During this procedure, the doctor can look at the shape of the womb as well as any other abnormalities such as fibroids and the thickness of the womb lining.
There are some small risks as with any invasive procedure which including bleeding, infection and damage to the cervix, however these are rare and would be discussed in more detail before it takes place. After the hysteroscopy has finished it is normal to feel some period type pains and bleeding for a few days afterwards, it is important to avoid the use of tampons due to risk of infection, but use sanitary towels instead.
A fibre-optic instrument is inserted through the abdominal wall to view the womb.
A pelvic ultrasound scan
A pelvic ultrasound uses sound waves to make a picture of the womb.
What is the treatment for uterine abnormalities?
Operating on the womb is not normally performed because it is linked to later infertility and carries a risk of any scar opening during the pregnancy.
Once you have been diagnosed as having an abnormally-shaped womb you will be put into the care of an obstetric team and you will have extra scans and hospital visits to check up on you and your baby throughout the pregnancy.
If your baby ends up in an awkward position (upside-down or bottom first for example) in later pregnancy you will be offered a caesarean section.