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Screening tests for women planning a pregnancy

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Introduction

Screening a woman’s blood before or during pregnancy allows a doctor to identify conditions which have the potential to adversely impact on her health, or the health of her developing baby (foetus). It is a fundamental component of health care during pregnancy, as many diseases can be treated or managed to reduce the risks to the mother and the baby’s health if they are identified in a timely manner.

An apparently healthy pregnant woman can carry diseases which do not cause symptoms, but which can have serious consequences if left untreated during pregnancy.

Blood screening for pregnancyA pregnant woman may be unsure if she has ever been infected with or vaccinated against vaccine-preventable diseases. In this case, blood screening can be used to determine whether or not the woman is infected with or carries antibodies to particular diseases (antibodies which she would have acquired due to prior infection with or vaccination against that disease).

Blood screening tests are ideally conducted before a woman becomes pregnant, as if vaccinations or treatments for existing disease are required, it is often safer to provide these while the woman is not pregnant (e.g. because some vaccinations present health risks to the foetus if administered during pregnancy).

Doctors recommend that all women undergo screening tests either before or during pregnancy. A doctor will need to obtain the woman’s consent to take her blood for screening. The doctor will provide detailed information about the screening procedure, the implications of the results (what the woman can/will need to do if the test result is positive) and the type of information that can be obtained by performing the tests.

In Australia, there are a number of screening tests which doctors recommend pregnant women undergo. However, some tests are performed only when the woman has a high risk for certain diseases (e.g there is a history of the disease in the woman’s family). During a preconception or antenatal care consultation, a doctor will need to ask detailed questions about the woman’s medical history (including details of any previous pregnancies) and conduct a physical examination (including genital examination). These enquiries provide the doctor with information about the woman’s risk for particular infections and allow the doctor to recommend appropriate screening tests.


Blood tests recommended for all women who are pregnant or planning a pregnancy

Routine pregnancy screening tests

Blood group and antibody screen

All women should have their blood screened at the first antenatal visit (the first pregnancy check up which should occur before the woman is twelve weeks pregnant). Blood screening enables the doctor to determine the woman’s blood type (whether she has type A, B, AB or O). Women who already know their blood type will not need to have this test.

Blood screening for pregnancyA doctor will also need to determine whether the woman has Rh- or Rh+ blood. The partners’ of women with blood type Rh- should also have their blood type tested because foetuses conceived by Rh- women and Rh+ men may develop haemolytic disease of the newborn, a serious condition which can cause brain damage and infant death. This disease occurs after an Rh- woman is exposed to the blood of her Rh+ foetus and begins producing antibodies which cause the body to reject Rh+ blood. These antibodies are passed onto the foetus during pregnancy, and can cause a newborn baby with Rh+ blood to reject its own blood following childbirth. This disease can be prevented by treating the pregnant woman and newborn baby with immune globulin, which prevents the formation of antibodies to Rh+ blood.

In addition to having their blood type tested, all women should be screened for blood antibodies. This is important even if the woman had previously has a test for blood antibodies, as antibodies concentrations change over time. For example, a woman who has previously been vaccinated and acquired antibodies for measles, mumps and rubella may require a booster vaccination is she has not been vaccinated for a long time, as antibody levels decline over time. Ideally, antibody screening should be performed before the woman becomes pregnant, as many vaccines are not recommended for use during pregnancy because there are hypothetical concerns about their safety when used during pregnancy.

Rubella (German measles) antibody status

Women need to have their blood assessed to determine whether or not they carry antibodies for Rubella at the first antenatal visit. It is necessary for a woman to undergo this test every time they become pregnant. Women who have previously been shown to carry rubella antibodies should not assume that they have sufficient antibodies, even if previous tests have shown sufficient rubella antibodies. Rubella immunity may decline over time, particularly in situations where women are immune due to vaccination (rather than natural infection). Rubella vaccines are not recommended for use during pregnancy, and it is therefore important to screen for the disease and vaccinate if necessary prior to becoming pregnant.

Syphilis serology

A blood test for syphilis infection should be performed at the first antenatal visit. Syphilis is a sexually transmitted infection which is often asymptomatic, meaning that many women who carry the disease do not have any symptoms and do not know they are infected. Syphilis can have serious negative effects during pregnancy, but is easily treated with antibiotics once detected.

Midstream urine

A woman will usually also have her urine tested at the first antenatal visit.

Viral infections

Doctors recommend that all women test for Hepatitis B, Hepatitis C and Human Immunodeficiency Virus (HIV) infection before or during pregnancy. As these are diseases with serious implications for both the pregnant woman and her foetus, women should take the time to fully discuss any concerns they have with their doctor.

Hepatitis B

Blood screening for pregnancyAround 1% of the Australian population are hepatitis B positive. As hepatitis B is highly infectious and can be easily transmitted to a newborn baby or hospital staff, it is recommended that all pregnant women are screened for Hepatitis B in the first trimester of pregnancy. The babies of women who test hepatitis B positive will require Hepatitis B vaccination at birth to reduce their chances of becoming infected.

Hepatitis C

Hepatitis C infection remains low in Australia with around 0.5% of the population infected. However, up to 80% of individuals in high risk groups (e.g. injecting drug users) carry this infection. During childbirth there is a 5% risk of transmission to the newborn. There is also a risk of infection for clinicians exposed to the body fluids, especially blood of hepatitis C carriers.

It is therefore recommended that all pregnant women are screened for Hepatitis C antibodies. Individuals who test positive for hepatitis C will require a second test to determine whether they are infectious or chronic (non-infectious) carriers of the disease. Knowing whether or not a pregnant woman can infect others with hepatitis C enables health workers to develop a management strategy to reduce the risk of the infection being transmitted during childbirth.

Having a caesarean section does not reduce the risk of hepatitis C transmission to the newborn, so hepatitis C carriers can deliver their baby naturally. However, their babies should be screened for hepatitis C infection between 12-18 months of age. Hepatitis C carrying women should breastfeed, like all other women, as there is no evidence that Hepatitis C can be transmitted through breastmilk.

HIV

Women should test for HIV during the first antenatal visit and again at 28 weeks pregnancy. While HIV infection rates amongst pregnant women in Australia are low, the disease has serious consequences and can be transmitted from a mother to her newborn baby during delivery or breastfeeding. The likelihood of a woman transmitting HIV to her baby is between 25-30% if she does not take any precautionary measures. However, the likelihood of infection can be substantially reduced (to about 2%) if appropriate preventative measures are implemented during pregnancy, childbirth and breastfeeding.

All HIV positive women planning a pregnancy (and those already pregnant) should be referred by their general practitioner for consultation with an infectious disease specialist. The infectious disease specialist will plan a series of preventative measures to reduce the woman’s risk of transmitting HIV infection to her baby. Usually women will need to take antiretroviral therapy during pregnancy and their babies will also require antiretroviral therapy for six weeks following birth to reduce the likelihood of transmission. A caesarean section delivery and intravenous antiretroviral treatment during delivery also reduces the chance of a woman transmitting the infection to her baby. As HIV can be transmitted via breastmilk, it is recommended that HIV positive women formula feed their infants.

Tests which may be considered at the first antenatal visit

Cervical cytology (PAP smear)

Blood screening for pregnancyWomen who have had a PAP smear within the recommended screening interval (two years) need not have the test performed again during pregnancy. However, there is no evidence that performing a PAP smear during pregnancy is dangerous, and women who are overdue for screening need to be tested at the first antenatal visit.

Vitamin D

It is important to screen women at risk of vitamin D deficiency. These women include those:

  • Who have dark skin;
  • Who wear a veil;
  • Who have little exposure to sunlight.

Women found to be deficient will be treated with vitamin D supplements throughout pregnancy and breastfeeding.

More information on Supplements in Pregnancy.

More information on Supplements in Breastfeeding.

Screening for haemoglobinopathies (blood disorders)

Some women may require additional screening tests for haemoglobinopathies (hereditary disorders of the blood in which haemoglobin production is abnormal). A doctor will determine whether or not these tests are necessary, based on the results of routine blood screening tests.

Varicella (chickenpox)

Screening for varicella (chickenpox) antibodies may be conducted on women who have never had or been vaccinated against chickenpox, or those who are unsure if they have ever been infected with or vaccinated for this disease. However, as varicella vaccine is not recommended for administration during pregnancy, screening for varicella antibodies is ideally conducted before the woman becomes pregnant.


Summary

Women who are planning to become pregnant should visit their doctor and undergo screening tests before they conceive. This allows the doctor to administer any necessary treatments or vaccinations to the woman before she becomes pregnant, and while the treatments/vaccinations do not pose a risk to the health of the woman’s foetus. Some blood tests are recommended for all women, while others are only recommended for women who have a high risk of certain diseases or conditions during pregnancy.

More information

PregnancyFor more information about pregnancy, including preconception advice, stages of pregnancy, investigations, complications, living with pregnancy and birth, see Pregnancy.

 

Sexually transmitted infections (STIs)
For more information on different types of sexually transmitted infections, prevention of STIs, treatments and effects on fertility, see Sexually transmitted infections (STIs).

 

References

  1. Royal Australian and New Zealand College of Obstetricians and Gynaecologists. Antenatal screening tests. 2008. [cited 2009, August 24], Available from: [URL link]
  2. Australian Government Department of Health and Ageing and National Health and Medical Research Council. The Australian Immunisation Handbook. 9th ed. Updated July 2009. [cited 2009, September 1]. Available from: [URL link]
  3. Royal Australian and New Zealand College of Obstetricians and Gynaecologists. Hepatitis B. 2007. Available from: [URL link]
  4. Royal Australian and New Zealand College of Obstetricians and Gynaecologists. Hepatitis C. 2007. [cited 2009, August 24], Available from: [URL link]
  5. Royal Australian and New Zealand College of Obstetricians and Gynaecologists. Guidelines for the use of Rh (D) Immunoglobulin in Pregnancy. [cited 2010 July 30]. Available from: [URL link]
  6. Royal Women’s Hospital. HIV and Pregnancy. 2006. [cited 2010, July 30]. Available from: [URL link]

 

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Dates

Posted On: 10 August, 2010
Modified On: 8 May, 2018

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