Screening in pregnancy is routinely offered for a number of conditions. Women should be given evidence-based information and should be informed about the purpose of any screening test before it is performed. All women have the right to accept or decline any test, and this should be made clear. Consent for screening tests does not have to be in writing.

Screening in pregnancy includes urinalysis (urine testing) for the following:

• ketones (caused by fat breakdown as a result of unmet foetal demands, for example through vomiting)
• glucose (as a result of higher circulating blood glucose levels, reduced glucose threshold of the kidneys, or disease)
• protein (as a result of vaginal leucorrhoea, a urinary tract infection, or high blood pressure disorders.)

Urine tests are carried out at all appointments.

Other screening tests are carried out on blood samples. Prior to blood screening, women should be provided with unbiased information on screening and diagnostic tests. The consequences and meaning of both screening and diagnostic tests should be explained. The minimum information that a woman should be given includes:

• the fact that all the tests will be carried out on blood samples
• the length of time it will take for test results to come back
• who will supply the test results
• who will discuss management of the pregnancy as a result of the test
• who the patient should contact if they have any further questions or are worried about anything.

Blood tests are carried out to screen for:

• anaemia
• Down’s syndrome
• blood group and rhesus factor
• blood disorders, for example sickle cell disease or thalassaemia (see below for further information)
• syphilis (the Venereal Disease Research Laborarory, or VDRL test)
• HIV
• immunity to rubella
• hepatitis B virus, in order to lower the risk of transmission to the baby during birth, therefore lowering the risk of illness and death of the baby as a result.

The National Institute for Clinical Excellence guidelines Antenatal care. Routine care for the healthy pregnant woman contains guidance on the routine antibody screening that is recommended in pregnancy.

Antibody screening is followed by titration, to measure the levels of the antibody in the blood. During pregnancy the antibodies routinely screened for are rhesus factor and rubella.

Rhesus factor

If a woman is rhesus negative and her baby is rhesus positive, she can develop anti-D antibodies. In subsequent pregnancies with rhesus positive babies, these maternal antibodies can cross the placenta and destroy the baby’s red blood cells. This can cause haemolytic disease (abnormal break up of the baby’s red blood cells) in the newborn. If the mother’s rhesus factor is known prior to the birth through screening, then this situation can be prevented. A rhesus negative mother who has had a rhesus positive baby should be given anti-D Ig (immunoglobulin) within 72 hours of birth (or any other sensitising event). This destroys any of the baby’s antigens that have crossed the placenta and entered the mother’s blood stream and which would cause the production of the anti-D antibody in the mother. As a result, the mother will not produce the anti-D antibodies that could cause haemolytic disease in babies resulting from subsequent pregnancies. Click here to view NICE guidance on the use of routine anti-D prophylaxis for Rh-D-negative women.

Rubella antibody

Primary rubella infection in the first trimester of pregnancy can cause devastating consequences in the baby. It is therefore considered important that mothers lacking the rubella-specific antibody, rubella-specific IgG, or immnoglobulin G (which confers immunity to the infection) are identified. These women can be immunised after the birth, to protect them in subsequent pregnancies.

All women should be offered screening for rubella early in their first pregnancy. Screening is carried out using a blood sample.

Given the current low incidence of rubella in the UK, it is probable that the rubella screening strategy will, at some stage, be reviewed by the National Screening Committee.

All pregnant women are offered (although they can decline) routine screening for rubella antibody, syphilis, HIV and hepatitis B in their first and all subsequent pregnancies. These can all be tested for from one blood sample. Pregnant women arriving in labour, who have not received antenatal care, should also be offered screening. Priority in these cases should be given to hepatitis B and HIV screening, and action should be taken on preliminary results, if necessary, until the results can be confirmed.

Screening should only be performed with documented consent, although this does not require a signature from the patient.

The other infection that is routinely screened for during pregnancy is asymptomatic bacteruria, a urine infection which is detectable through culture of a urine sample. Untreated, this condition can cause severe problems and affect the outcome of the pregnancy, and as it is asymptomatic, it is unlikely that the condition would otherwise be detected.

Screening for the following infections are not routinely offered to pregnant women in the UK:

• chlamydia trachomatis (due to the insufficient evidence on both its effectiveness and cost-effectiveness)
• cytomegalovirus
• hepatitis C virus (due to the insufficient evidence on both its effectiveness and cost-effectiveness)
• group B streptococcus (as evidence on both its effectiveness and cost-effectiveness is currently uncertain)
• toxoplasmosis (as the potential harms of screening could outweigh the benefits)
• asymptomatic bacterial vaginosis, as evidence suggests that the identification and treatment of this condition does not lower the risk of preterm birth.

The National Institute for Clinical Excellence (NICE) guidelines Antenatal care. Routine care for the healthy pregnant woman contains guidance on the routine screening for infectious diseases that is recommended in pregnancy.

Infection with the hepatitis B virus (HBV) is a major health problem worldwide. It is a bloodborne virus that can be transmitted in several different ways, the most frequent of which is from mother to baby during pregnancy and childbirth. For further information on the disease in pregnancy, see hepatitis B and for further information on prevention of transmission and precautionary measures for healthcare personnel, click here.

Due to the high transmission rates from mother to baby during pregnancy and breast feeding and the potential effects on the baby, hepatitis B is one of the infectious diseases that is routinely screened for in pregnancy. Screening should be offered at the first and all subsequent pregnancies, and as early as possible.

In order for a pregnant woman to make an informed choice about whether or not to be screened for hepatitis B, she should be told:

• what hepatitis B is and why screening is offered
• about the routes of transmission (particularly mother to child)
• how the test is carried out (i.e. blood test), how long the results can take and what they might mean
• what can be done to protect her baby if she (the mother) is found to test positive for the virus
• about her rights to take time to consider her decision and that she can decline the test
• about further sources of information and advice.

Some women may be concerned about the test, for example about any effects the results may have, for instance on her relationships. Any such concerns should be discussed and explored with care and sensitivity. Some women may benefit from appropriate counselling to help them reach a decision.

Whether the test is accepted or declined, midwives should use the woman’s notes to record the fact that the test was offered. As with other antenatal investigations, verbal consent is sufficient. If in the unlikely event that a woman refuses screening, midwives should explore her reasoning, but must not pressurise or overrule her.

A woman’s HBV status should remain confidential wherever possible. However, if the baby is to receive the appropriate immunisation essential to its own health, it is important to disclose this information, for instance to other health professionals who may be involved in the mother’s and baby’s care. This will include her family doctor and health visitor.

Information on hepatitis B testing in pregnancy, aimed at midwives, is housed on the Department of Health website.

Women testing positive for infections such as HIV and hepatitis B, should have their test results explained to them in person and should be offered specialist counselling and support. This should take account of any relevant cultural issues. Counselling should also be available to the woman’s partner and family if required.

Subsequent discussions should include any course of action, such as ways to reduce the chance of transmission from mother to baby (for example, delivery via elective Caesarean section in the case of HIV, and immunisation for the baby in the case of hepatitis B). If the patient requires specialist counselling, they should be referred according to local recommendations.

A pregnant woman who tests positive for infections such as hepatitis B or HIV should be referred according to your department or unit. For example, women with particular social difficulties, such as those with immigration or housing problems, will require significant input from social services. Those who use drugs will need support from drug dependency specialists. It is important that a woman diagnosed with a disease such as HIV, is supported by a carefully documented and detailed plan of care and multidisciplinary meetings. Counselling should include all aspects and implications of the disease, which should be addressed over several visits. The woman should be reassured that her confidentiality will be respected, although it should also be explained that personnel involved in her and the baby’s care need to be aware of her HIV status.

Informing a woman of a negative test result should offer the opportunity to raise general sexual health issues. It is also an opportunity to explain the dangers of becoming infected with sexually transmitted diseases, such as HIV and hepatitis B, during pregnancy or during the period in which she is breast feeding.

Serological testing of babies to assess a diagnosis of HIV is of limited value in the first six months due to the presence of maternal antibodies and the need for the child to mount its own immune response to the disease.