Screening during pregnancy
During your pregnancy, you may be referred for a variety of tests and checks. Some tests, such as urine and blood type, are recommended for all pregnant women and are used to check your health and that of your baby. Others, such as amniocentesis and chorionic villus sampling, are for women who may be at a higher risk of developing particular conditions, or health problems. Your midwife, or GP, can help you and your partner decide what is best for you and your baby, and they will also be able to help you to understand the purpose, risks, and benefits of each test.
You can decline to have these tests, but they can provide information that will help ensure that you deliver a healthy baby.
The tests may be done at your GP surgery, the local clinic, or at the hospital antenatal department. Some of the tests that you may have while you are pregnant are outlined below.
- Blood type test - this is to check to see if you have a blood type known as rhesus negative. If you are rhesus negative, and your baby has inherited a rhesus positive blood type from the father, the mismatch of blood types can sometimes cause your body to produce antibodies (proteins which fight infection) which attack the baby's red blood cells. This condition can be treated with an anti-D injection straight after birth.
- Hepatitis B - this is a virus which can cause liver disease, and may infect your baby if you are carrying the virus. Your baby can be immunised straight after birth to stop it from developing the condition.
- HIV testing - this is the virus that causes AIDS. If you are HIV positive, you can pass the infection on to your baby during pregnancy, delivery, or breastfeeding. If your test shows you are HIV positive, you and your baby can have treatment to help minimise the risk of your child developing the condition.
- Anaemia - this is a condition caused by a lack of iron in your blood. It means that you produce fewer red blood cells, leaving you weak, tired and lethargic. If your test shows that you have anaemia, you may have to take iron supplements (see the 'recommendations' section).
- Syphilis - this is a sexually transmitted infection (STI). If you test positive for syphilis, you must receive treatment as soon as possible because, if left untreated, this infection can cause miscarriage and stillbirth.
- Rubella - also known as German measles, rubella can seriously harm your unborn baby. Most women are immune to the condition because they have been vaccinated as a child. If your test shows that you do not have the antibodies to fight the disease, it is important that you avoid contact with anyone who has rubella. If you have rubella, you and your baby will require treatment to try and prevent any complications.
- Urine tests - the sugar levels in your urine will be tested because some women develop diabetes during pregnancy. Your urine will also be tested for protein, as its presence may indicate that you have an infection.
Ultrasound
An ultrasound scan uses high-frequency sound waves to provide an image of your baby. The scan is completely painless, and there are no known serious side effects to you or your baby. You may have to have several scans during the course of your pregnancy, depending on how your baby is developing. An ultrasound scan may be used to:
- determine the size and age of the baby,
- check the position of the baby and placenta,
- check for physical problems in the baby, or placenta, and
- determine a multiple birth.
You will normally be asked to drink plenty of fluids before the scan. This is because a full bladder pushes the womb up, and provides a better picture. A special jelly is put on to your stomach, and the ultrasound instrument is moved back and forward over your skin.
Alpha-fetoprotein test
An alpha-fetoprotein test is usually performed at around 15-20 weeks of your pregnancy to check for the amount of alpha-fetoprotein (AFP) in your blood. If you have a high level of AFP, it could be an indication that your baby has spina bifida (where the baby's spine does not develop properly). If you have abnormally low levels of AFP, it could be a sign that your baby has Down's syndrome. If your AFP levels are abnormal, further testing may be required.
Amniocentesis
Amniocentesis is a test that is offered to some women after 14 weeks of pregnancy to check for any possible genetic disorders. If you are at increased risk of having a baby with Down's syndrome, for example, you have had a low AFP test result, or if your ultrasound showed that your baby has a genetic-related abnormality, then you will have this test.
During the amniocentesis test, a fine needle is passed through your abdomen and into the amniotic fluid (the fluid which surrounds and protects your baby). A small sample of the fluid is taken for testing, and is analysed to check for genetic disorders. The procedure usually only causes mild discomfort, although there is a 0.5-1% risk of miscarriage. Results can take up to three weeks to come back.
Chorionic villus sampling (CVS)
Chorionic villus sampling (CVS) is also offered to some women to test for genetic disorders. It is usually performed at 11 weeks of pregnancy, and can detect conditions such as cystic fibrosis (a condition that causes a build-up of mucus in the lungs) and muscular dystrophy (where the muscles slowly, progressively waste away). A needle is inserted through the abdomen, and a small sample of placenta is taken. The risk of miscarriage is slightly higher than it is for an amniocentesis test, at 1-2%.