Routine antenatal tests explained
Blood group and antibody testing. It is important to know whether your blood group is "negative" or "positive". Women who have a "negative" blood group (also called "Rhesus negative" or "D negative") may need extra tests and treatment to prevent complications for their baby.
A full blood count is performed at least twice during pregnancy to check for anaemia or other blood conditions that could affect you and your baby's health. A low red blood cell count may indicate iron deficiency anaemia or a genetic condition such as thalassaemia. Your doctor will explain any abnormal blood results with you and arrange appropriate testing.
Some infections can be carried without any symptoms and may cause problems during pregnancy, or be passed on to your baby at birth and potentially lead to long term health problems. Testing for a range of conditions including: hepatitis B, hepatitis C and HIV, syphilis, rubella and urinary tract infections are offered to all pregnant women.Testing for other infections, such as varicella (chicken pox), chlamydia, gonorrhoea may also be performed. If you are worried about a particular infection, you should speak with one of our midwives or doctors. Important information on how to prevent infections during pregnancy can be found here.
Women and their partners have the option of being tested to find out if their baby is at risk of an inherited genetic disease, even if there is no history of an affected individual in the family. This type of testing is called carrier screening and is available for several of the most important genetic conditions. These currently include thalassemia, cystic fibrosis, spinal muscular atrophy and fragile X syndrome. Further information on carrier screening for couples without any history of a genetic disease can be found in the resource section below.
Every baby has a small chance of having a chromosomal or genetic condition. Prenatal screening for chromosome conditions is offered during pregnancy to provide women and their partners with more information about their unborn baby. The most common chromosomal cause of birth defects and intellectual disability in children and adults is Down syndrome. Down syndrome has been the major focus of prenatal screening because it is common (occurs in about 1 in 400 pregnancies) and because it has major effects on health and learning. An online decision aid to help you navigate the options for prenatal screening can be found here.
Your blood sugar levels are crucial to your baby's growth and development. Gestational diabetes is a condition where your body cannot regulate your blood sugar levels properly during pregnancy. An oral glucose tolerance test (OGTT) is recommended to all pregnant women at 26-28 weeks of pregnancy to check for gestational diabetes. An OGTT requires a bit of planning and at least 2 hours of your time. You must be fasting (nothing to eat or drink for at least 8 hours) for the first blood collection. You will then be given a solution containing 75g of glucose to drink within 5 minutes. You blood sugar level will then be tested one hour and two hours after this drink.
Your blood pressure should be checked at each antenatal visit. Your urine should also be checked with a "dipstick" for protein at each visit after 20 weeks gestation. An elevated blood pressure or abnormal protein in your urine may be a sign of a pregnancy complication such as preeclampsia, which can affect your health and your baby. If this is suspected, further blood pressure measurements, urine testing, blood tests and assessment of your baby's well being may be needed.
The size of your pregnancy belly will be assessed during your routine antenatal examinations. Your doctor or midwife will also ask you about your baby's movements once you are over 20 weeks gestation. If you have any concerns about your baby's movements, you should come in for assessment without delay. See resources below for further advice on monitoring your baby's movements.
Ultrasounds are performed at several stages during pregnancy. Early scans in first trimester help confirm your due date and whether you having having one baby or twins. A scan at 11-13 weeks is performed as an early screening for fetal abnormalities (including Down syndrome or structural abnormalities). A 20 week scan is performed to check on fetal development, the position of the placenta, and the length of your cervix (which tells us if you are at increased risk of preterm birth).
At 36 weeks, a low vaginal swab is taken to test for a bacteria called Group B "Strep". This is a normal bacteria that lives in the bowel or vagina in about 15% of women. If if is present in the vagina at the time of labour and birth, then there is a small chance (about 1in 200) of your baby developing a serious infection from this bacteria. We are able to prevent this by giving antibiotics (penicillin) during labour.