Antenatal testing and screening tests in pregnancy
The aim of antenatal care is to safeguard the health and well-being of both mother and baby during pregnancy. It enables obstetricians to identify potential problems in the early stages of pregnancy which, if not addressed or treated, could result in increased risk for mother and baby.
The initial antenatal visit is often the first time a woman has a detailed medical history and physical examination recorded with specific laboratory testing. The visit can provide information about the woman which may alter the management of her pregnancy and provide for her long-term health care. Prior knowledge of a woman's medical history or family background can also assist the obstetrician.
As with any test or procedure, antenatal testing and screening is undertaken following informed consent of the woman after adequate and appropriate counselling with regard to the implications, limitations and consequences of each investigation.
Tests recommended at the first antenatal visit of each pregnancy
- Blood group and anti-body screening, which determine the woman's blood group (A, B, AB or O) and if the blood is positive or negative for the Rhesus (Rh) factor. If the woman's blood is Rh(D) negative, then problems may arise if her baby's blood is Rh(D) positive. Women who are Rh(D) negative are tested again for the presence of positive anti-bodies later in pregnancy
- Full blood examination. This test measures the amount of haemoglobin in the red blood cells. A white cell count will also be conducted. This test will give some information about anaemia and iron deficiency
- Rubella (German measles). The blood is tested for antibodies from a previous rubella infection or vaccination
- Syphilis. If detected, syphilis needs to be treated in the mother for her health and well-being and to protect the baby from infection
- Midstream urine test, which tests for urinary tract infection
- Human Immunodeficiency Virus (HIV). If a woman tests positive for HIV, treatment during pregnancy can reduce the risk of infection being passed to the baby
- Hepatitis B and Hepatitis C screening tests
- Cervical cytology if there has not been a recent Pap smear
Other antenatal tests that may be considered and discussed are:
- Haemoglobinopathy screening (Thalassaemia) in at risk women
- Varicella (or chicken pox). Screening for varicella antibodies where there is no history of previous infection
Tests that are recommended after the antenatal visit
- Obstetric ultrasound at 18 to 20 weeks' gestation for growth and well-being
- Screening for Down syndrome: This depends on timing: a) At 11 to 13+6 weeks gestation, a first trimester ultrasound scan for nuchal translucency and maternal serum screening, known as the combined test. b) At 15 to 17 weeks gestation, a second trimester maternal serum screening blood test can be performed
- Further testing for Rh(D) positive antibodies at 28 weeks in Rh negative women
Other tests that may be offered
- Screening for gestational diabetes, eg testing for glucose tolerance
- Screening for Group B streptococcal disease (GBS). Testing for GBS is usually conducted at 35 to 37 weeks. If GBS is present, antibiotics are prescribed as a preventative treatment to protect the baby from infection during labour
- Full blood examination or iron deficiency assessment in the third trimester
The above is a list of recommended tests for women without specific additional risk factors. Other antenatal tests may be discussed during a woman's antenatal care. The list is not exhaustive and further reading and information is required to gain a more thorough understanding of how they are considered during pregnancy.
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