Abnormalities of the uterus causing infertility

What are abnormalities of the uterus?

Your uterus (womb) is a pear-shaped organ, tucked away in your pelvis. A normal uterus is about 7.5cm (3in) long, 5cm (2in) wide and 2.5cm (1in) deep. Inside, it is hollow with thick muscular walls. The lower part of the uterus dips down into the vagina and is called the cervix. The upper portion is called the fundus. The fundus is the part where the fertilised egg grows into a baby.

A small number of women have a uterus (womb) that differs in shape or structure from the norm. This is called an abnormality of the uterus, or a uterine abnormality. It is a bit of a catch-all phrase, and the figures reflect this. Between one woman in 20 and one woman in 100 has a uterine abnormality.

However, it’s difficult to know exactly how many women have an abnormality, because it’s possible to have one without knowing it. In fact, some women only find out when they try for a baby. One woman in 13 who seeks help for infertility turns out to have some sort of uterine abnormality.

 

Problems of the uterus and uterine lining that can cause or contribute to reproductive problems such as infertility or recurrent miscarriage:

  • Uterine Polyps
  • Uterine Fibroids (proper medical terminology is myoma or leiomyoma)
  • Intrauterine adhesions – scar tissue within the uterine cavity, also called Asherman’s Syndrome. This can interfere with conception, or can increase the risk of a miscarriage.
  • Congenital uterine malformations, such as a bicornuate uterus, a T-shaped uterus, or a uterine septum
  • Luteal phase defect – an uncommon condition that involves inadequate development of the microscopic and cellular changes in the endometrial lining of the uterus after ovulation and exposure to the hormone progesterone.
  • Thin endometrial lining – this is also uncommon. We like to see a lining of at least 8mm in thickness when measured by ultrasound at the time of maximal thickness during the cycle (see above ultrasound picture of an 11.2 mm lining).

There is some debate about “how thin is too thin”, as well as to “how thick is too thick”.

  • In general, 8-13 mm is good, less than 6 is potentially a problem, and greater than 15 or so might possibly reduce chances for successful pregnancy.

During IVF treatment, the uterine lining starts at about 3mm thick at the end of the menstrual period. After estrogen levels rise sufficiently, the lining of the uterus thickens by about 1mm each day during IVF.