Pregnancy and Cancer

04 April 2019

What are the common types of cancer that is present during pregnancy?

Generally cancer during pregnancy is uncommon and the estimated incidence is 1 in 1000 pregnancies. Overall, the odds of getting cancer rise with age. Many women are now delaying childbirth until their late 30s or 40s, resulting in rising incidence of cancer in pregnant women.

Cancers seen in pregnant women are also those commonly seen in younger patients such as breast cancer, cervical cancer, thyroid cancer, lymphoma and melanoma. The most common cancer seen in pregnant women is breast cancer, which tends to occur in 1 in 3000 pregnancies. As such, most of the information on cancer treatment in pregnant patients are collected from pregnant breast cancer patients. 

Are there any reasons why these cancers are present during pregnancy?

There is no obvious causal link between pregnancy and cancer. In some breast cancer studies it was discovered that the majority of breast cancers diagnosed during pregnancy are hormone receptor negative, which means that they are not dependent on the high levels of the female hormones present during pregnancy. Therefore there is no evidence to show that there is any changes in the pregnant patient that predisposes them to developing cancer. Usually it is just an unfortunate coincidence.

Will cancer itself harm the unborn baby?

Some cancers may spread to the placenta – the temporary organ of the womb that connects and nourishes the baby via the mother. However, most cancers do not spread directly to the unborn baby. It is the cancer treatment that affects, as some can cause harm to the baby.

How is cancer diagnosed during pregnancy?

The diagnosis of cancer in pregnant patients are usually delayed because some symptoms of the cancer may be mistakenly attributed to pregnancy. For example, pregnant patients may experience engorgement of the breasts, nausea & vomiting, abdominal bloating, headaches and constipation. The symptoms of cancer can be easily overlooked because of this.

If a lump is found for e.g. in the breast/neck, pregnant patients can have an ultrasound scan which does not involve any radiation. In some hospitals, a mammogram for a breast lump investigation is also done as it is considered safe with shielding of the patient’s abdomen with a lead shield during the mammogram to minimise radiation to the unborn baby.  For other types of cancer, other investigations like a pap smear for cervical cancer or a lymph node/thyroid gland biopsy are also considered safe in pregnancy.

Computed tomography scans (CT scans) are generally avoided if possible especially for CT scans of the abdomen /pelvis as ionizing radiation is used and this may harm the unborn baby. However, CT scan of the head & neck region may still be carried out with shielding of the patient’s abdomen with a lead shield and minimal radiation to the unborn baby.  Other investigations that involve ionizing radiation such as a PET CT scan are contraindicated but those that do not involve ionizing radiation such as  MRI scans are considered safe.

Does the pregnant cancer patient have to abort the baby ?

This is a misconception that many people have about pregnancy and cancer.

The treatment of cancer in a pregnant patients is complex and complicated. So the medical team involved needs to have a thorough discussion with the patient with regards to the treatment options. Some chemotherapy drugs are considered safe in pregnancy after the first trimester (see below) and some surgical procedures are also considered safe in late pregnancy. As more information and data is collected about pregnant cancer patients, it is becoming clear many pregnant patients go on to deliver healthy babies.

Therefore the pregnant cancer patients can still have cancer treatment options and still carry on with the pregnancy.

At the end of the day, the decision is a personal one but one that needs to be done following a good discussion with the medical team looking after the patient.

Who are involved in the care of the pregnant cancer patient?

As the care of the pregnant cancer patient is complex, the medical team involved should include her gynaecologist/obstretician, medical/radiation oncologist and a neonatologist/paediatrician.

What treatment options are available to the pregnant cancer patient?

Many factors are considered when making treatment decisions for all cancer patients.

In the pregnant cancer patient, the doctor has to balance the benefit of any cancer treatment to the mother and the risks of any harm to the developing baby.

Treatment options will depend on the patient’s overall health condition, the type & stage of the cancer (size of the tumour, extent of disease involvement and the spread to other organs in the body) as well as the stage of the pregnancy.

Surgery during pregnancy

In many types of cancer, surgery is the only curative treatment. In some cases, chemotherapy may be used prior to surgery to shrink the cancer to facilitate surgery or for a better outcome of surgery.

Generally, the 2nd trimester is considered the safest time for surgery as the risk of  a miscarriage and preterm labour is lower. The doctor will have to consider the safest but also the most appropriate surgery for the types of cancer the pregnant patient has, for e.g. a mastectomy (total removal of the breast) versus a lumpectomy (only removal of the cancerous part) in breast cancer patients.

Special consideration is required for anaesthesia,  optimal positioning of the patient on the operating table for surgery to ensure maximal blood supply to the unborn baby as well as any medication given post-operatively. During the surgery, there will be close monitoring of both the patient and her unborn baby. The patient’s blood pressure and oxygen level as well as the baby’s heart rate will be closely monitored.

In some circumstances where the cancer is detected at an early stage during later in pregnancy, the medical team involved may consider both options of delaying treatment till delivery or inducing the birth of the baby early. Usually, induction of labour is only considered after 32 weeks but doctors may precribe steroids medication to help the unborn baby’s lungs to mature before the induction. Inducing labour in a pregnant cancer patients may be difficult and stressful, so a caeserean section may be considered. The medical team looking after the pregnant patient will have a thorough discussion with the patient and her family regarding the options for a best possible outcome for both mother and baby.

Chemotherapy during pregnancy

Chemotherapy during the 1st trimester is avoided as this is the crucial period where the unborn baby’s vital internal organs are developing.  However, chemotherapy during the 2nd trimester has been reported to be safe. Only certain chemotherapy drugs will be used based on the data collected all over the world of pregnant patients who had these certain chemotherapy drugs during the 2nd trimester and went on to deliver healthy babies. Doctors will avoid chemotherapy treatment late in 3rd trimester to avoid any complications of chemotherapy at the time near to the baby’s birth.

Studies looking at children exposed to chemotherapy prenatally did not show an increased in any developmental problems.

Radiotherapy during pregnancy

Radiotherapy or radiation treatment for cancer is treatment using high doses of X rays (ionizing radiation). As there is very little research/experience in radiotherapy in pregnant patients, doctors tend to avoid using radiotherapy in pregnant cancer patients. This is because the radiation doses used for radiotherapy cancer treatment are much higher than that used for diagnosis purposes.  

Targeted therapy or hormonal therapy during pregnancy

Targeted therapy is the use of drugs that specifically target molecules/proteins in the cancer cells that regulates or play a major role in the growth of the cell and progression of the cancer whereas hormonal therapy is the use of drugs that block the effects of hormones on the cancer growth. Generally targeted therapy and hormonal therapy are both avoided during pregnancy as the effect of these drugs on the developing baby is not fully known. Therefore if targeted /hormonal therapy is indicated in the treatment of the pregnant cancer patients, it is usually started only after the birth of the baby.

Can I breastfeed my baby during cancer treatment?

This very much depends on the treatment that the patient is on after the birth of the baby. During chemotherapy breastfeeding is not advisable as the drug may be excreted in the breast milk. With regards to targeted therapy/hormonal therapy, breastfeeding is also not advisable as not much is known about the effects of these drugs on the baby as these drugs are also excreted in the breast milk. However, patients can still breast feed if they are getting radiotherapy on other parts of the body or in breast cancer, the other breast that is not getting treatment.

Can treatment wait until the baby is born?

This depends on the patient’s type & stage of cancer as well as the stage of the pregnancy. In some cases where the cancer is threatening the patient’s life, then treatment should not be delayed. The decision to delay treatment has to be made with consultation of the patient’s medical team.