The aim of prenatal tests is to conduct a screening and diagnosis for any existing problems that may

• affect the health and well-being of the mother or baby,
• identify and address problems if any,
• Assess the risk of a baby having a chromosomal or genetic disorder.

Commonly done pregnancy tests may be classified as follows:

I. Tests done during Pre-conception or immediately after conception.

1. Tests done during Pre-conception or immediately after conception.
2. These tests are done to rule out inherited diseases. These tests will help to understand the risk of having a child with one of any such diseases. Genetic testing for abnormal hemoglobin, abnormal chromosomes etc. fall in this group.
3. Rubella Test
   Woman infected with rubella virus during early pregnancy can transmit the disease to the fetus, causing serious birth defects such as congenital heart disease or stillbirth. Therefore, it is recommended that all girls should take the rubella vaccine to prevent such complications in pregnancy. The rubella test is done for a woman who wants to become pregnant to determine whether she is at risk for rubella. A positive rubella IgG test result means that the lady cannot get the infection. A negative result means that she is not immune and there can be an infection during the pregnancy.
4. Human immunodeficiency virus (HIV) screening test
   This is to check for HIV infection so that steps can be taken to reduce likelihood of transmission of the disease to the baby.
5. Tests for STD (sexually transmitted diseases)
   Tests for gonorrhea and syphilis are done in persons with suspected history. These infections can cause miscarriage or infection to the bay during delivery.

II. Tests recommended during the first prenatal visit

1. Pregnancy Test
   Human chorionic gonadotropin (HCG) level in blood is increased. This is to confirm pregnancy. This will be positive within a few days of conception.
2. Fasting blood glucose and HbA1c estimations
   These are used to screen women at risk of type 2 diabetes or their Pre-diabetic stage. Women with diabetes are strongly encouraged to have HbA1c test at least 3 to 4 months before they wish to conceive. This is because diabetes-related birth defects happen early in pregnancy, well before most prenatal visits. Controlling the blood sugar helps to prevent birth defects and miscarriages. Diabetes may be diagnosed a) if the fasting blood sugar is more than 126 mg/dl or b) random blood sugar level is more than 200 mg/dl or c) when glycated hemoglobin (HbA1c) level is more than 6.5%. Criteria for diagnosis of pre-diabetic state is when a) fasting blood sugar is more than 110 mg but less than 126 mg/dl or when HbA1c level is 5.6% and 6.4%. Fasting blood glucose and HbA1c test for women at risk of type 2 diabetes may be repeated, if necessary.
3. TORCH panel (Toxoplasmosis, rubella, cytomegalovirus(CMV), herpes simplex (TORCH) panel) These infections can cause birth defects.

III. Tests usually done during First Trimester (up to 12 weeks of pregnancy)

1. Urine culture for bacteriuria
   This will detect bacterial infection in the urinary tract, which can lead to kidney infection or increased risk of preterm delivery and low birth weight. This may be repeated in third trimester also.
2. Urine screen for glucose
   Check for undiagnosed diabetes or gestational diabetes. Repeated during each prenatal visit.
3. Urine screen for protein
   High blood pressure and the presence of urine protein are indicative of preeclampsia, which may lead to eclampsia (fits) during late pregnancy. Repeated during each prenatal visit.
4. Complete urine analysis
   Urine may be tested for red blood cells which will indicate urinary tract infection.
5. Complete blood Count (CBC)
   
   1. White blood cell (WBC) or leukocyte Count: White blood cells protect the body against infection. During bacterial infection, the number of white cells rises.
   2. WBC differential count: The major types of white blood cells are neutrophils, lymphocytes, monocytes, eosinophils and basophils. Too less count of these white blood cells indicated an infection.
   3. Red blood cell (RBC) count: Red blood cells carry oxygen. Anemia is diagnosed, if the RBC count is low.
   4. Hematocrit (HCT) or packed cell volume (PCV): This is test measures the volume of red blood cells in the blood. In anemia, hematocrit value will be reduced.
   5. Hemoglobin (Hb): The hemoglobin present in red blood cells carries oxygen.
   6. Red blood cell indices: The mean corpuscular volume (MCV) shows the size of the red blood cells. The mean corpuscular hemoglobin (MCH) value is the amount of hemoglobin in an average red blood cell. The mean corpuscular hemoglobin concentration (MCHC) measures the concentration of hemoglobin in an average red blood cell and help in the diagnosis of anemia.
   7. Platelet (thrombocyte) count: They are important in blood clotting which helps to stop the bleeding. Too few platelets may result in uncontrolled bleeding.
6. Blood Test for ABO typing
   Rh (Rhesus factor) typing
   If a pregnant woman with Rh-negative blood is carrying a fetus with Rh-positive blood, Rh sensitization may occur. This happens when the baby’s blood mixes with the mother’s blood during delivery. This cause the mother’s immune system to make antibodies against the baby’s red blood cells in future pregnancies. This can destroy the red blood cells of the baby, leading to severe problems (Rh disease). If Rh disease is not treated, the fetus or newborn may die. The test is usually done in the first trimester; antibody screen is repeated between weeks 28 and 29 of pregnancy. If the pregnant lady is Rh negative, blood should be tested for Rh antibodies and if found, she may be given Rh immunoglobulin immediately after delivery to prevent her making antibodies hence preventing further Rh immunization.
   Direct and indirect coombs test
   The direct coombs test detects antibodies that are already attached to red blood cells. The indirect coombs test detects antibodies that are present in the blood –stream and could bind to blood cells. This will lead to autoimmune hemolytic anemia.
   First trimester Down syndrome screen
   This will assess the risk of carrying a fetus with chromosomal abnormalities such as down syndrome-usually done between 11 and 14 weeks of pregnancy.
   Hepatitis b virus (HBV) tests
   HBV is transmitted through infected body fluids, including blood, semen and vaginal fluids. It also can be transmitted from a pregnant woman to her child at or near the time of birth.
   1. Hepatitis b surface antigen (HBsAg): shows an active infection. The presence of HBV antigens means that the virus is present in the body.
   2. Hepatitis b surface antibody (HBsAb): shows past or present infection and leads to protection against HBV for life.
   3. Hepatitis b e-antigen (HBeAg):is present during an active HBV infection. Testing is used to monitor the effectiveness of treatment for HBV.
   4. HBV DNA Testing: The quantity of DNA can help determine how severe the infection is. This test is used to check the effectiveness of treatment for chronic HBV infection.

IV. Tests usually done during the second trimester (13 – 27weeks of pregnancy)
Urine screen for glucose: urine screen for protien: Blood glucose is repeated during each visit.

• ultrasound diagnostic imaging test will be done usually as part of their routine prenatal care, often between weeks 18 and 20.This will indicate problems with the baby's organs such as heart and also help to assess the baby's growth and health.
• Quad Screening is done usually between 15 to 18 weeks of pregnancy. it measured levels of four substances (alpha feto protein, hCG, unconjugated Estradiol and dimeric inhibin) in blood. These are secreted by the fetus and are found in the blood of all pregnant women. Very high or low values may indicate fetal abnormality such as down's syndrome, neural tube defect (NTD) or abdominal wall defect. Screening tests will indicate the possibility of fetal abnormality but they are not diagnostic. If Screening tests are positive, then further diagnostic test should be done.
• Chorionic villus sampling is offered to women who are at an increased risk of having a baby with chromosomal or genetic abnormalities.

V. Tests usually done during the Third Semester(from 28 weeks of pregnancy to delivery)
urine screen for glucose;urine screen for protien;blood glucose are repeated during each visit. Complete blood count(CBC) may be repeated. RBC antibody screen may also be done.

1. The pregnant women may be given a non – stress test (NST). This non – invasive test,given after 28 weeks, is used in high – risk pregnancies or to monitor baby's health and look for distress sighn. The test measures the fetal heart rate as it relates to movement.
2. Fetal heart rate monitoring measures the fetus's heart rate and rhythm.
3. Fetal ultrasound is a test to get an image of the baby in the uterus. It is a non-invasive way to check the health of an unborn baby. During a fetal ultrasound, The Baby's heart, head and spine are measured.