Fibroid in Pregnancy

What is a fibroid?

A uterine fibroid is a benign, firm, usually roundish, swelling (tumour) that develops within the muscular wall of the uterus (womb).

A fibroid can vary in size from being as tiny as a pea to as large as a melon. Fibroids are very common. The figures quoted vary, but it is estimated that between 25 per cent and 80 per cent of women have a fibroid or fibroids if you look very carefully. In a typical case a woman will have several fibroids present within her uterus and these will usually be of varying sizes.

Fibroid tumours are benign (they are not cancerous and do not spread to other parts of the body). They usually cause no symptoms at all and are often present without a woman knowing that she has them. If they become larger then they are more likely to result in symptoms or problems such as pain or discomfort. If fibroids enlarge and distort the endometrium (lining of the womb) then they cause heavy periods.

Having a fibroid during pregnancy and the potential problems it can cause.

Gynaecologists in the past used to be concerned that a fibroid may grow quickly due to the rising oestrogen levels in pregnancy and cause major problems. Recent medical research has shown that most fibroids do not actually become larger during pregnancy, and those that do often return to their pre-pregnancy size afterwards.

However, there are several ways that a fibroid may affect a pregnancy.

A uterine fibroid can cause uncomfortable feelings of discomfort, pressure, heaviness or even pain if they grow larger and press on surrounding organs or pelvic structures. A fibroid may lead to sharp pain in the lower back (lumbar region) and legs if there is pressure on a nerve.

A rare complication of a fibroid during pregnancy is a problem known medically as red degeneration. If red degeneration occurs there is haemorrhage within the centre of the fibroid. This usually happens in the middle trimester (three months) of pregnancy and is thought to result from the leiomyoma (fibroid tumour) growing rapidly and outgrowing its blood supply. Red degeneration can be very painful, usually requires treatment with strong painkillers, but nearly always settles down without causing serious problems or needing specific treatment.

With regard to falling pregnant, fibroids are thought to account for about two to three per cent of all infertility problems. If a fibroid or fibroids develop just under the endometrium (surface lining of the uterus) this may affect the way in which a fertilised egg attaches or implants in the endometrium of the womb.

A fibroid therefore, may cause recurrent early miscarriage, which is often so early that a woman is not even aware that she has been pregnant.  More rarely a fibroid may obstruct the canal of the cervix or the opening of the fallopian tubes into the womb. Sometimes later in pregnancy, fibroids may also disrupt the normal development and growth of the uterus, leading to premature labour and childbirth. Extremely rarely, fibroids may lead to a miscarriage before 23 weeks of pregnancy.

The most frequent problem with fibroids in pregnancy is that they can lead to slightly early labour and delivery of the baby two to three weeks early, which is of very little threat to the baby.

Rarely a fibroid can develop and enlarge in the lower part of the uterus and lead to cause partial blockage of the birth canal. If this happens, then a caesarean section operation is usually necessary to deliver the baby.

When a woman who is having infertility problems is discovered have uterine fibroids, they may be treated and removed they are sufficiently large, to try and increase the likelihood of conception. Gynaecologists usually advice that small fibroids are best left untreated.

Medical research has indicated that if there is cause found for the fertility problem, treating and removing the fibroids increases the chance of falling pregnant by about 40% to 80%.

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