Routine Tests in Pregnancy
A range of tests are recommended during pregnancy to make your pregnancy safe, check and assess the development and well-being of you and your baby, as well as screen for conditions. Some tests are done at almost every check-up. A few others are done only at certain times during pregnancy, or if you have certain problems. Blood tests and urine tests are two routine tests conducted during pregnancy.
Blood tests are done to know your blood type (A, B, AB, or O; Rh positive or Rh negative), immunity to German measles (rubella), and haemoglobin levels. The tests also reveal if you are suffering from conditions such as hepatitis B, syphilis or AIDS.
You will be asked to give a urine sample at each prenatal (medical and nursing care offered during pregnancy) visit. This test determines the levels of protein and sugar in your blood. Sugar levels higher than normal are an indication of diabetes during pregnancy, which can be treated. Also, proteins in urine may be a sign of urinary tract infection or kidney disease that also needs to be treated.
Screening for Birth Defects
What are birth defects?
Birth defects are structural or functional abnormalities that are present at birth. These defects occur while a baby is developing in the mother's body. Some of these are clinically obvious at birth; however, some may be diagnosed much later in life.
What are the various screening tests performed?
Screening tests help to know about a pregnant woman's risk of having a baby with certain birth defects. These are done during the first and second trimesters of pregnancy.
First trimester screening tests
Screening tests in the first trimester are done between 11 and 14 weeks and include blood tests and ultrasound exam to detect the risk of Down syndrome and trisomy 18. These results along with the mother's age detect Down syndrome in approximately 82-87% of the cases.
Second trimester screening tests
Screening tests in the second trimester are usually performed between 15 and 20 weeks. They involve detecting a protein and three hormones. The presence of these hormones alone indicates Down syndrome in 69% of the cases and detecting all four (the protein and the three hormones) indicates Down syndrome in 81% of the cases. Also, neural tube defects can be predicted in a good number of cases if the protein is detected in blood.
The tests of the first and second trimester screenings can be combined to confirm birth defects such as Down syndrome in a relatively larger number (90-95%) of the cases.
Positive screening tests are usually followed by diagnostic tests for further information.