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02 August 2022

Fibroids and pregnancy

By Dr. Wee Horng Yen
Obstetrician and Gynaecologist
MB BCh BAO (Dublin), MRCOG (London), FAMS (Singapore)

Pregnant mom holding a flower against her belly

What are fibroids? 

Fibroids are non-cancerous tumours that grow in or around the womb (uterus) and are very common. The growths are made up of muscle and fibrous tissue and vary in size from under 1 cm to over 20 cm. Fibroids are sometimes known as uterine myomas or fibromyomas.

Many women are unaware that they have fibroids as they do not have any symptoms. This often means that fibroids are diagnosed by chance during a routine gynaecological examination, test, or scan.

However, larger fibroids may cause swelling in the lower tummy, pain, difficulty passing urine, a feeling of bulge while bending or constipation.  If the fibroid impinges on the uterine cavity (the area where the baby grows), it may cause difficulty conceiving, miscarriage, or heavy and painful periods. 

Fibroids that cause difficulties in conceiving require treatment.  Surgery is the mainstay of treatment. Surgery can be performed using a keyhole or a traditional open (bikini line cut).  If the fibroids are only in the uterine cavity, a hysteroscope can be used to remove them through the vaginal route without leaving any scars.

Patients whose fibroids are not too large may be offered keyhole surgery.  Rarely in Singapore do patients present with fibroids that are very large, over 15 cm; occasionally a midline scar is needed for access to the tumour.

Keyhole surgery has the advantages of less pain, a shorter stay in hospital, and smaller scars.

After surgery, the surgeon will advise the patient on the duration of rest before they may conceive.  This may be any time after three months post-surgery.  Some patients will require a caesarean section for all future deliveries after fibroids are removed.  This is to prevent rupture of the uterine scar during labour.

In the longer term, fibroids may recur, requiring future surgery.

Fibroids during pregnancy

One of the more common complications of large fibroids in pregnancy is “red degeneration”.  This can cause moderate to severe pain and may be hard to tell apart from contractions of the uterus.  When blood goes to the growing baby instead of the fibroid, red degeneration can happen.  The reduction in blood and oxygen to the fibroid causes pain and the fibroids may shrink.

Rarely, fibroids within the uterine cavity may cause miscarriage. Very large fibroids may be associated with preterm birth. The majority of fibroids remain about the same size throughout pregnancy and do not cause major complications.

As long as the fibroid is not physically obstructing the passage of the baby, women with fibroids may undergo natural birth.

Fibroids noted at caesarean section 

It is not routine to remove fibroids at caesarean delivery.  This is because of the increased risk of bleeding in doing so. The exception is when the fibroids are “sticking out” or at the surface.  In these cases, the base of the fibroid is much smaller and it may be safely removed.