Having cancer tests while pregnant

If your GP or pregnancy doctor thinks there may be a link between your symptoms and cancer, they will refer you to a hospital specialist. Tests to diagnose cancer can usually be done without harming the baby.

Tests for cancer during pregnancy

If your GP or pregnancy doctor thinks there may be a link between your symptoms and cancer, they will refer you to a hospital specialist for tests. Making sure you are well is the most important thing for having a healthy baby. So it is important to find the cause of your symptoms.

You may worry that tests could put the baby’s health at risk. Tests to diagnose cancer can usually be done without harming the baby. Your doctors will choose tests that do not risk exposing the baby to harmful amounts of radiation. They will try to avoid:

If they think you need a test they would usually avoid, they will talk to you about it. Your doctor will explain how they can reduce any possible risk to the baby.

If you have had tests and later find you are pregnant, talk to your doctor. With most tests there is no risk to the baby, or if there is it is a very small risk.

Ultrasound scans

An ultrasound scan uses sound waves, not x-rays, to build up a picture of the inside of the body. You may have already had one during your pregnancy to check the baby’s development. There is no risk to the baby.

You can usually have an ultrasound on most parts of the body depending on your symptoms.

For example:

  • if you have gynaecological symptoms, you may have an ultrasound of your pelvis (lower tummy area between your hips)
  • if you have breast symptoms you may have an ultrasound of your breast and armpit
  • if you have digestive symptoms, you may have an ultrasound of the tummy or liver in the upper tummy area.


You can have x-rays if they do not directly expose the baby to the rays. For example, you could have x-rays of your head, chest and arms and legs. The person taking the x-ray (radiographer) places a lead shield over your tummy to protect the baby. Doctors sometimes call this pelvic shielding.

Mammogram (breast x-ray)

It is safe to have a mammogram to check your breasts during pregnancy. The amount of radiation is very low and will not harm the baby. But the radiographer still shields your tummy area to protect the baby.

MRI (magnetic resonance imaging) scan

An MRI scan uses magnetism to build up a detailed picture of your body. It does not use x-rays. There is no evidence that MRI scans are a risk to the baby. But doctors will try to avoid them in the first 3 months (first trimester) of pregnancy.

You are given a contrast injection (gadolinium) with an MRI scan to give a better picture of the scan area. This may pass through the placenta and be harmful to the baby during the first trimester.


A biopsy is a common test to diagnose cancer. Your doctor takes a piece of tissue or small sample of cells from the area to check for cancer cells.

You may need a biopsy to:

  • check a lump
  • remove a lymph node (gland)
  • remove a mole or freckle on the skin. Most biopsies in pregnancy are done using a local anaesthetic to numb the area. Having a local anaesthetic is safe during pregnancy.

If you cannot have a biopsy using a local anaesthetic you may need a general anaesthetic. If your pregnancy is at an early stage, your doctor may recommend waiting until you are over 14 weeks pregnant (second trimester) to have a biopsy.

Bone marrow biopsy

A bone marrow biopsy takes a small sample of bone marrow for testing. Bone marrow is the spongy material in your bones where blood cells are made. The sample is usually taken from your hip bone. This test is safe during pregnancy.

Colposcopy and biopsy

This test uses a microscope called a colposcope to look closely at your cervix. They may take a small sample of cells (a biopsy) from the cervix to test for cancer cells.

You may have this if a cervical screening test taken before pregnancy showed abnormal cells on the cervix. Some women have it to check vaginal bleeding during pregnancy when other possible causes have been ruled out.

The cervix is at the entrance to the womb so you only have a biopsy if it is necessary. If you are further along in your pregnancy, your specialist may recommend leaving the biopsy until after the baby is born.

There is more risk of bleeding during this type of biopsy in pregnancy. Your doctor may do the biopsy in an operating theatre. They may recommend you have it done under a general anaesthetic.

Waiting for test results

Waiting for test results can be a difficult time. It may take from a few days to a couple of weeks for the results of your tests to be ready.

You may find it helpful to talk with your partner, your family or a close friend. Your specialist nurse, Mummy’s Star and different cancer support organisation can also help.