What are Prenatal Tests?
Prenatal tests are done during pregnancy, to check your and your baby’s health. These tests help in detecting conditions that can put a baby at risk such as preterm birth, etc, if not treated well. With a prenatal test, you can also determine other birth defects or chromosomal abnormalities.
Some screening tests are also considered prenatal tests which can help reveal the possibility of a problem. Other prenatal tests such as diagnostic tests can determine whether the fetus has any specific problem or not. Sometimes, based on the situation a screening test is done followed by a diagnostic test.
So, if your doctor is recommending you to go for a test, then he is trying to analyze the risks if involved. Routine tests always help keep a close tab on you and your baby. That is why it is very important to keep a note of all your prenatal appointments.
These tests include:
History and physical exam – You’ll have to answer questions about your health and family history during your first or second prenatal visit. This information can help your doctor to analyze and address the risks, such as inherited genetic disorders. You will also have to undergo a physical exam, wherein your doctor will calculate the due date based on the date of your last menstrual period.
Pelvic exam and Pap smear – Prenatal tests during the first trimester begins with a pelvic exam and Pap smear, to help check the health of your cervical cells. This test also checks for cervical cancer and STDs (Sexually Transmitted Diseases).
Blood tests – During one of your first visits, your blood group will be identified, and therefore you will be screened for anaemia, checked for immunity to Rubella, and tested for Hepatitis B, HIV, Syphilis, and other STDs.
Based on your family background, you will be offered certain tests and genetic counselling to help assess risks for diseases such as Cystic fibrosis, Tay-Sachs, Sickle cell anaemia. Certain other diseases can also be detected with saliva.
You might also be tested for diseases such as varicella and toxoplasmosis. Your hCG levels will also be checked. hCG (Human Gonadotrophin) is a hormone that is secreted by the placenta, and progesterone, which helps maintain the pregnancy.
Urine tests – You will be asked for your urine sample, so that your doctor can look for signs of kidney infection, and can confirm your pregnancy, by checking your hCG levels. Your urine sample will also detect if you are having any gestational diabetes or preeclampsia.
In the later part of your first trimester, you will also be requested for genetic testing. Some pregnant women feel that these tests may cause them stress, but most of them ensure that the baby is genetically normal after delivery. There are many genetic testing options available that involve blood tests alone or sometimes even an ultrasound that involves no risk for your growing baby.
Down syndrome and other genetic conditions will also be screened by combining a blood test with an ultrasound. This type of screening takes place between 11 and 14 weeks of pregnancy. With all screening methods, CVS – a more invasive diagnostic technique will be used, if the results are positive.
Noninvasive prenatal testing (NIPT) – This cell-free fetal DNA test is done after 10 weeks of pregnancy. NIPT uses a blood sample to identify the quantity of free fatal DNA that is present in the mother’s blood. You can not only determine Down syndrome through this test, but also some other chromosomal abnormalities.
Chorionic villus sampling (CVS) – If you are a pregnant woman and aged 35 or more, with a family history of certain chronic diseases, then you will be offered this type of invasive test, majorly between 10 and 12 weeks of your pregnancy. Through CVS, your doctor will be able to detect many genetic defects such as Down Syndrome, Cystic fibrosis, Sickle cell anaemia, Muscular dystrophy, and Hemophilia.
The procedure involves inserting a tiny catheter through your cervix or inserting a needle into your abdomen region and taking a tissue sample from the placenta. Hence, this procedure can carry a 1% risk of inducing miscarriage and 98% helps in ruling out certain chromosomal birth defects. But when compared to amniocentesis, CVS cannot help in detecting any neural tube defects, such as anencephaly and spina bifida, or abdominal wall defects.
What Other Tests Might Be Offered During Pregnancy?
Your doctor might also order other tests during your pregnancy based on your and your partner’s medical history and other risk factors. Hence, it is advisable to speak with a genetic counsellor, if your growing baby is at risk for any hereditary conditions.
Other diagnostic or screening tests include:
- Hepatitis C
- Thyroid disease
- Cytomegalovirus (CMV)
- Tay-Sachs disease
- Fragile X syndrome
- Canavan disease
Remember that these tests are only offered to you by your doctor, only when you want to have them.
To decide which tests are right for you and which are not right, discuss with your doctor why a test is so necessary, its risks and benefits, and what risks or diagnoses can be decided based on the tests done.