Pregnancy and Lab Testing

During pregnancy, a fetus develops inside a woman’s uterus and is eventually born as an infant after a period of approximately 9 months. There are a number of clinical lab tests that can be used before, during and after pregnancies. These tests give out useful information from the conception phase to the initial days of the newborn’s life.  

The main purpose of prenatal tests is to screen for and diagnose any existing problems that could affect the baby’s or the mother’s health, discover, and address any issues that could arise, and assess the risk of the baby developing a genetic or chromosomal disorder. These tests generally require a small sample of easy to obtain urine, blood, or cervical cells.  

Some of the tests are conducted before a childbirth at various stages of the pregnancy. Others are performed when necessary, usually to detect and address some problems or conditions that could arise during pregnancy. Still, there are others that are typically offered to women who have an increases level of risk due to their age, genetic factors, etc.. In contrast, others are selectively conducted based on the family and personal medical histories of the woman and her partner.  

In the following pages, you’ll find information about many of the routine tests, and even some not-so-routine tests. Your healthcare practitioner might recommend extra tests depending on your medical history. It makes sense that expectant mothers are advised to have a discussion with their physicians about testing. Reliable internet sources (e.g., the U.S. Centers for Disease Control and Prevention and the March of Dimes) and healthcare professionals can help you understand the benefits and risks that come with each test.  

To know more about these tests and which ones might be run before or during your pregnancy, be sure to read the following.  

Preconception Tests 

Tests for Immunity to Rubella (or German Measles) 

Rubella is a disease caused by a virus, which is usually spread from a person to another person through sneezes and coughs. Any contact with the throat or nasal secretions of an infected person can spread the virus. Women who’ve have received the vaccination or have had a rubella infection before will have an antibody in their body that prevents them from getting the disease the second time. The antibody effectively protects the fetus against the virus, and this protection is referred to as immunity.  

Rubella infections that occur during childhood often cause just mild symptoms. Nonetheless, if a woman becomes infected with Rubella during her first 3 months of pregnancy and doesn’t have immunity to the Rubella virus, the baby will be at risk of developing serious birth defects.  

Any woman considering a first-time pregnancy, or those who get pregnant for the first time, should get this test to see if they have this immunity. A blood specimen will be tested to see if there’s a sufficient number of antibodies present to protect the woman and the fetus from the virus. In case a woman doesn’t have enough antibodies and is not yet pregnant, she can get vaccinated against rubella. She should then delay getting pregnant for at least 28 days.  

The rubella vaccination constitutes a weakened form of the virus and so shouldn’t be administered to a woman who’s already pregnant. When an expecting woman doesn’t have enough antibody to protect herself and her baby, her healthcare provider will likely advise her to avoid contact with any persons with symptoms of rubella throughout her pregnancy. She should also consult with her healthcare provider about the best time to get the vaccination once her baby is born, and then follow through with it to ensure that her next baby is protected.  

HIV 

Human immunodeficiency virus (or HIV) testing has become a routine prenatal care procedure in the U.S. Some states even have requirements that all pregnant women and their newborns be tested. For pregnant women who test positive for HIV and start treatment during pregnancy, it’s possible to prevent the disease from transferring to the child and even improve the health of the mother. Nonetheless, not all women will receive the test or prenatal care during their pregnancy, and some simply don’t agree to have the test done. Essentially, most women will have the blood test as part of their early pregnancy care or pre-conception care. This serves to protect both the baby and the mother.  

Screening the mother: In the U.S., all pregnant women should be counseled about HIV early on in their pregnancy and receive voluntary HIV tests to protect the health of the child. This is recommended by many groups, including the American Academy of Pediatrics, U.S. Public Health Service, U.S. Preventative Services Task Force, and the American College of Obstetricians and Gynecologists. It’s also wise to repeat the test in the third trimester, especially for those at high risk of contracting HIV.  

Screening the Baby: In the U.S., if the mother’s HIV status is not determined during or before the pregnancy or during labor and delivery, health professionals recommend a screening test for HIV, which is usually available as a blood test. Detecting both antigen and antibody in a combination test will increase the likelihood of an HIV infection being detected soon after exposure. There are some screening tests that will only identify the HIV antibody. These are available as tests of oral fluid or blood tests.  

In case the screening test is positive, it should be followed by a second antibody test that’s different from the first test. If the second test doesn’t agree with the first test, a third test will be performed to detect the genetic material of the virus (the RNA).  

When these confirmatory tests show an HIV infection, the woman should consider consulting with her healthcare provider about the risks of infecting the baby and how it could influence her health before getting pregnant. During pregnancy, HIV infected mothers could start treatment, take certain precautions at birth, and avoid breastfeeding to minimize the risk of passing the infection to their child. Intravenously administering zidovudine, an antiretroviral drug, during labor and delivery as well as to the newborn twice a day by mouth for 6 months will reduce the rate of transmission from about 25% to 33% to approximately 1% to 2%. Integrating different antiretroviral therapies is the most effective way of reducing the risk of HIV transmission to the newborn.  

A negative result for the antibody to HIV could mean that there’s no infection or that the body has not produced a sufficient amount of the antibody. If the woman engages in high-risk activities that increase the risk of contracting HIV, such as intravenous drug use or unprotected sex contact, she should retest one or more extra times during the pregnancy.  

Chlamydia, Gonorrhea, and Syphilis 

Chlamydia, gonorrhea, and syphilis are some of the most common STDs (or sexually transmitted diseases) caused by bacterial infections. For pregnant women, these infections can infect the baby before or during delivery, or even lead to a miscarriage. After birth, a baby might have serious health issues, such as breathing problems, eye infections, blindness, blood or joint infections, etc. Some of these problems could be life-threatening, and the health of the woman will also be endangered by the STD. The best approach here is usually for the woman to take antibiotics to cure the infection before delivery or before the pregnancy.  

All women in the U.S. should be tested for these STDs before planning a pregnancy, or early on in their prenatal care, like during the first prenatal hospital visit. When a woman is younger than 25 years old, and they are at risk or otherwise engage in high-risk activities during their pregnancy, it’s important to retest them for STDs later on in their pregnancy.  

Gonorrhea and chlamydia tests will detect the presence of bacteria in the provided sample. Some of the tests use a cervical swab or a urine sample. When the test comes out positive, the person is considered to have a current STD infection that will require prompt treatment.  

Syphilis is tested through a blood test. It is intended to detect antibodies produced in the body in response to the infection. The test will, however, not distinguish between a past or a current infection, meaning if it comes out positive, confirmatory testing might be required. A negative test normally means that the woman isn’t currently infected, though it’s still possible that an infection is too recent to be detected. Some states require all women to be screened for syphilis during their delivery.  

According to the CDC, many people don’t usually know when they have an STD, and some healthcare professionals don’t routinely screen for STDs. Tests for some STDs need to be done routinely during the prenatal care as early treatment will decrease the chance the baby contracts the disease. Other STDs of concern during pregnancy include herpes, trichomoniasis, hepatitis B, and hepatitis C, along with HIV. Screening for each of these diseases should be made part of the first prenatal visit, ideally as early in the pregnancy as possible. This is according to the guidelines outlined by the CDC.  

When planning for a pregnancy, or at your early prenatal visits, be sure to ask your health practitioner about the STD tests appropriate for you and your partner at that time, and again in your third trimester.  

HPV Testing and Pap Test 

A Pap Test is mainly used to screen the cervix (the opening to the uterus) for any form of pre-cancerous changes, cancer, inflammation, and some kinds of STDs. HPV testing will effectively detect the high-risk forms of human papillomavirus, which is responsible for increasing the risk of developing cervical cancer in women. A number of health professional organizations have the following recommendations: 

  • Pap tests and screenings should start no earlier than the age of 21 years 
  • Women between ages 21 and 30 need to have a Pap test every 3 years 
  • Women between ages 30 and 65 years should do a Pap test and HPV test every 5 years (recommended); a Pap test done every 3 years is also okay 

In a lot of cases, if a woman tests negative in the regular Pap test and/or the HPV test within the recommended interval, they won’t need to have the test done when she gets pregnant. However, if the recommended time interval has already elapsed since the last cervical screen, or if there are any concerns or questions regarding the health status of the cervix, then the healthcare practitioner might suggest pre-conception screening or during the early stages of a pregnancy.  

Early detection and early treatment of infections, the high-risk types of HPV, and abnormal cervical cells will offer the best chances of preventing any major problems from arising and/or progressing and potentially impacting the health of the baby and the success of the pregnancy.  

Screening Hepatitis B and Hepatitis C  

Contracting hepatitis viruses can cause the inflammation of the liver. Severe hepatitis might exhibit symptoms like nausea, fatigue, and jaundice. While people usually recover without major medical intervention, some may eventually develop a chronic infection. Some of the chronically infected might have progressive liver damage that could cause liver cancer and even death.  

Hepatitis B: The screening test for hepatitis B is commonly referred to as Hepatitis B surface antigen. The test is designed to detect a protein produced by the virus in the body, and it can detect the infection even before it causes symptoms. When a woman who is considering getting pregnant test positive for hepatitis B, she should consult with her healthcare practitioner about how long she should wait to allow the infection to heal before getting pregnant.  

It’s imperative that active hepatitis B infection be detected early in pregnant women because newborns are especially susceptible to developing a chronic infection – up to 90% of people who are infected with hepatitis B in utero become active carriers. In case a hepatitis infection is detected in an expectant mother, she can be monitored, and the baby can receive the proper treatment at birth to reduce the risk of developing hepatitis B.  

Testing negative for the Hep B virus means that there’s either no infection in the body or that there are no sufficient antigens to be detected. When a woman regularly participates in high-risk activities that make them vulnerable to contracting hepatitis, retesting later on in the pregnancy is generally recommended.  

Hepatitis C: While not a very common infection, hepatitis C can be passed down from a woman to her baby. Screening pregnant women for hepatitis C is not routine, though it might be done if the mother is particularly at risk of infection. Some of the risk factors of hepatitis C include having a sexual partner who uses intravenous drugs, using intravenous drugs, having a history of multiple STDs, and being infected with hepatitis B.  

Screening the infection involves taking antibody tests.  Since the antibody test can stay positive in most people even once the infection has cleared, a positive antibody test will often be followed by an RNA test for hepatitis C, which detects genetic material from the virus. A positive result usually means the virus is present -the infection is not yet resolved – meaning the person will require additional treatment. The genotype from the hepatitis C test will determine the type of virus present and therefore guide the treatment.  

Varicella Zoster Virus (Shingles and Chicken Pox) 

The varicella zoster virus (or VZV) is responsible for causing chickenpox and shingles. While most pregnant women will have already been exposed to the virus and, therefore, a developed immunity against it, some may not have had the infection before, or have already been immunized. Considering that the virus can cause birth defects or illnesses in the baby based on when the infection occurs during the pregnancy, testing for VZV can be done before or early on in the pregnancy to establish whether the woman has antibodies for VZV.  

When a woman is already pregnant, she can’t receive the vaccination for VZV and should generally avoid coming into contact with anyone who has shingles or chickenpox. In case it’s determined that a pregnant woman might have been exposed to the VZV virus, treatment is available, and this can prevent or significantly weaken the severity of the disease.  

Women with special health considerations such as diabetes or high blood pressure should try getting these under control before getting pregnant. Any woman with type 1 or type 2 diabetes is encouraged to have an A1c test done at least 3 to 4 months before they get pregnant. That’s because most diabetes-related birth defects typically happen early in the pregnancy, and well before the prenatal visits. Performing this test will help the woman identify a safe time to try becoming pregnant. Getting pregnant when the blood sugar level is well controlled and maintaining tight control during the first trimester will help to prevent miscarriages and birth defects.  

Pregnancy: First Trimester (Up to 12 weeks) 

During the first prenatal visit, which typically takes place during the first trimester of the pregnancy, a healthcare practitioner might order a number of the tests described below in order to check for certain infections and conditions that might harm the unborn baby or the mother’s health during the pregnancy.  

Pregnancy Test (hCG) 

If the pregnancy is only suspected, or when the pregnancy test wasn’t performed by a healthcare practitioner (and was, for instance, conducted using an at-home urine pregnancy test), a pregnancy test might be done to confirm that the woman is pregnant.  

The pregnancy test will measure the human chorionic gonadotropin (or hCG), which is a hormone produced by the placenta when a woman is pregnant. The levels of hCG during pregnancy will increase steadily during the first trimester (first 8 to 10 weeks) of a normal pregnancy and will peak around the 10th week following the last menstrual cycle.  

There are generally two types of hCG tests: quantitative and qualitative: 

Qualitative tests are conducted on either blood or urine and are usually done following a missed menstrual period to confirm that a woman is actually pregnant.  

Quantitative tests usually measure the actual levels of the hCG in the body and are conducted on blood samples. Some labs might have targets for what the level of hCG should be each week during the gestation period in the first trimester, though each woman’s levels might vary as the exact gestation age might be uncertain. The key feature of the hCG in the first trimester of a pregnancy is that the levels should double every 2 to 3 days. In case there are any concerns about the pregnancy, the healthcare practitioner will measure the hCG levels several times to ensure that they are increasing at a normal rate.  

In cases where the hCG levels aren’t rising normally, it could be due to an ectopic pregnancy, which means the pregnancy occurred within the fallopian tube, which leads from the ovaries to the uterus, or more rarely, in the abdominal cavity (abnormal intrauterine pregnancy). Since an ectopic pregnancy might become a medical emergency, health practitioners might need to conduct vaginal ultrasound in patients whose hCG is not increasing appropriately to ensure that there’s a gestational sac within the uterus. 

RBC Antibody Screen and Blood Typing 

Blood Typing 

Blood typing is done within the first trimester or the first few prenatal visits. It’s mainly used to establish the blood group of a pregnant woman, whether it’s A, B, AB, or O, and whether she’s Rh-negative or Rh-positive. All pregnant women should know their blood type.  

Blood typing is essential during pregnancy, considering that the mother and the unborn baby could be of different blood types. For instance, if the mother is Rh-negative, the father is Rh-positive, the fetus might be Rh-positive by inheriting the Rh antigen from the father. In such a case, the blood types of the baby and the mother are different, and the mother’s body might decide to produce antibodies (antiglobulins) that attack or counteract the antigens (factors or proteins) produced in the fetus blood cells. These antibodies could cross the placenta and destroy the baby’s red blood cells, which results in conditions known as hemolytic diseases of the newborn. Although it’s unlikely that a first Rh-positive baby will become ill, the antibodies produced during the first pregnancy might affect any future Rh-negative babies.  

To substantially lower the chances that an Rh-negative mother develops this antibody, she can be treated with an injection of Rh immune globulin at about the 28th week of pregnancy. This Rh immune globulin will essentially bind to and mask the Rh antigen of the fetus, thereby preventing the mother from developing antibodies against it. There are some cases where additional injections are necessary during the pregnancy, such as when the mother has an abdominal injury, amniocentesis, chorionic villus sampling, and if the baby is Rh-positive after delivery. However, before every subsequent injection is administered, an antibody screening will be performed to ensure the woman hasn’t already developed Rh antibodies.  

Antibody Screen 

Along with the Rh-negative women who are expecting an Rh-positive baby, women who’ve had prior pregnancies or have had a blood transfusion might produce an antibody to other blood factors other than the Rh, which could potentially cause harm to the unborn baby. This screen is done during the first trimester and redone during the third trimester (28th or 29th week of pregnancy). It will determine whether there are any potentially harmful antibodies present in the mother’s blood.  

In case a harmful antibody is detected, the father of the baby is tested, where possible, to establish if his RBCs have antigens that the mother’s antibody could be targeting. If so, the RBCs of the fetus might also have antigens that might be targeted. This will have the healthcare practitioner monitor the antibody level in the mother as well as the health of the fetus for the duration of the pregnancy. Some signs that the fetus could be getting ill might require treatment before delivery, such as an early delivery or intrauterine infection.  

While Rh incompatibility typically has more severe consequences, one of the most common causes of the hemolytic disease of the newborn (or HDN) is the incompatibility between the baby’s and the mother’s ABO blood groups, not the Rh factor. Nonetheless, the RBC antibody screen can’t be used for predicting whether HDN will occur or not because the antibodies to the ABO blood groups are naturally occurring.  

Urine Screening for Protein and/or Glucose 

During the first, second, and third trimesters, each prenatal visit by an expectant mother might include giving a urine specimen, which will typically be tested in the office using a dipstick to check for the presence of protein and/or glucose (sugar). While trace amounts of both protein and glucose are usually present in urine, high levels could indicate a problem and might necessitate further testing.  

Protein 

Having a high protein level in urine is a major warning sign. It could indicate kidney disease or damage, it might be a transient elevation because of an infection, physical or emotional stress, or taking certain medications. Additional tests might have to be conducted to help establish the cause and may include a full urinalysis, a 24-hour protein test, or urine culture (used to identify any yeast or bacteria present).  

One primary concern during the 2nd and 3rd trimesters is pre-eclampsia, which is also referred to as toxemia or pregnancy-induced hypertension. This is a disorder usually characterized by large amounts of protein in the urine (happens in about 8% of pregnancies) and high blood pressure. The symptoms of the disorder include headache, sudden weight gain, inflammation, and vision changes. Risk factors include being African American, being pregnant with more than one child, first pregnancy, age (teenage women and those over the age of 40), and having pre-existing hypertension, diabetes, or kidney disease.  

The disorder could lead to a decrease in nutrition and air getting to the baby via the placenta, which could lead to low birth weight and other complications. However, when it’s caught early enough through routine monitoring of urine protein levels and blood pressure, the health problems for the mother and the baby due to toxemia can be managed effectively.  

Glucose 

High amounts of glucose in the urine might be a sign of undiagnosed diabetes already present in the mother. It could also be gestational diabetes, which can develop during pregnancy. A urine test that comes out positive is normally accompanied by an additional confirmatory blood sugar (glucose) test to check for gestational diabetes in the 2nd trimester, between 24 weeks and 28 weeks of pregnancy.  

Complete Blood Count (or CBC) 

This is a test designed to check the cells that circulate in the blood. Blood is made up of three kinds of cells, which are contained in a fluid known as plasma. They include platelets (PLTs), red blood cells (RBCs), and white blood cells (WBCs). To diagnose and prevent problems early, a CBC might be done before a pregnancy when possible, at the early stages of a pregnancy, and one or more times during the pregnancy. The first baseline results could be compared to the values obtained later on to check for any changes that might indicate a health issue.  

Red blood cells contain a protein known as hemoglobin, which is responsible for giving blood the red color. Hemoglobin binds to oxygen in the lungs and transports it throughout the body, eventually releasing the oxygen to different cells and tissues. When a woman is pregnant, her hemoglobin will be responsible for transporting enough oxygen to meet both her body’s needs and her fetus’. If the woman lacks sufficient hemoglobin and/or RBCs, then she is said to be anemic.  

Many expectant mothers will experience some form of anemia during their delivery. While this is usually not a problem, a small amount of blood loss can still be harmful to women with anemia. A healthcare practitioner might want to check the level of hemoglobin in a pregnant woman’s blood before they deliver their child to better evaluate the possible risks of the expected blood loss.  

White blood cells have many immune functions and are mainly responsible for protecting the body from infections. Assessing the WBCs during pregnancy could be helpful in detecting infections, which allows them to be treated and resolved before they can end up causing significant health problems to the mother and her baby.  

Platelets are a special form of cell fragments in the blood that help with clot formation to stop bleeding. Pregnant women who have a low platelet count or whose platelets don’t function appropriately in clot formation are at a risk of bleeding excessively during delivery. If a platelet problem is detected, follow up testing might be needed to help establish which treatment options are ideal.  

Urine Culture for Asymptomatic Bacteriuria 

Many organizations, including the Infectious Diseases Society of America (or IDSA), the American College of Obstetricians and Gynecologists (or ACOG), the U.S. Preventive Services Task Force (or USPSTF), and the American Academy of Family Physicians (or AAFP), recommend that pregnant women be screened for asymptomatic bacteriuria via a urine culture during the first prenatal visits or between 12 weeks and 16 weeks gestation period. If later, the ACOG recommends the first prenatal visit, and the test repeated in the 3rd trimester.  

Asymptomatic bacteriuria in pregnancy is usually diagnosed when a substantial amount of bacteria is present in the urine culture of a woman, although she’s not experiencing any symptoms associated with a urinary tract infection, such as urgency to urinate or pain while urinating. The condition affects 2% to 10% of pregnant women in the U.S. alone, and can lead to serious kidney infection or increase the risk of low birth weight and preterm delivery. It’s recommended that the infection is treated with the appropriate antibiotics.  

Selective Tests 

Hemoglobin or Blood Glucose A1c Testing for Women at Risk of Type 2 Diabetes 

Sometimes, a healthcare provider will recommend screening for pre-existing diabetes in pregnant women during the first prenatal visit or within the first trimester, especially if the woman has risk factors for diabetes, like family history. This is a bit different from the kind of diabetes that develops during pregnancy (gestational diabetes), which is regularly screened for in the 2nd trimester.  

A hemoglobin A1c, a fasting blood glucose, or a 2-hour glucose tolerance test might be used to identify pre-existing diabetes in pregnant women. An elevated blood glucose level could mean that the woman has diabetes. Of course, she will undergo additional testing to confirm that the diagnosis is accurate, and if positive, will start receiving treatment to manage the condition.  

There is a different set of tests used in diagnosing gestational diabetes.         

TSH (or Thyroid Stimulating Hormone) for Women with a History or at Risk of Thyroid Disease 

Pregnancy often leads to normal changes in the function of lots of endocrine glands, though it has a marked effect on the thyroid gland.   This particular endocrine gland is responsible for producing hormones like triiodothyronine (T3) and thyroxine (T4), which are critical to the healthy development of a fetus and the proper health of the mother.  

Pregnant women with pre-existing thyroid conditions will require a careful monitoring routine when they become pregnant. A healthcare practitioner might use tests for TSH to monitor the patient’s thyroid hormones throughout the pregnancy. TSH is produced in the pituitary gland located in the brain, usually in response to low T4 and T3 levels. Heightened TSH levels in women who are taking thyroid hormone replacement might signal that their dosage of hormone replacement should be increased.  

Some healthcare professionals advocate for checking for any signs of elevated TSH levels in pregnant women in their first trimester (or before pregnancy), even in cases where the woman doesn’t have a history of the thyroid disease. That’s because a significant number of women might have an underlying thyroid disorder that is unsuspected and might go undetected, only to cause problems during pregnancy. Nonetheless, most guidelines don’t point to this as necessary.  

TORCH Panel When Infection or Exposure is Suspected 

This is used when screening for certain infections that can lead to birth defects in a baby in case the mother contracts them during her pregnancy. The blood tests that make up the panel are usually for: 

•          Toxoplasmosis  

•          Rubella 

•          CMV (or cytomegalovirus) 

•          HSV (or herpes simplex virus) 

Some of these tests are usually ordered independently, either during or before a pregnancy. The complete TORCH panel test is not very common because there are more specific and sensitive tests that can be used to detect these infections.  

Some of the other infections that can be tested at the same time are hepatitis B, syphilis, varicella zoster virus, coxsackie virus, parvovirus B19, and Epstein-Barr virus.  

Bacterial Vaginosis (or BV) Screening When a Woman Shows Any Symptoms 

Bacterial Vaginosis is basically an overgrowth of the normal vaginal flora.  BV causes a vaginal discharge and is relatively common in women, pregnant or not. However, untreated BV during pregnancy could lead to premature rupture of membranes, amniotic fluid infection, low birth weight of the baby, premature delivery, and even pelvic inflammatory disease in the mother. While this test isn’t done routinely, a physician may order it for women who have the symptoms, especially if the woman had previously delivered a premature baby.  

Signs and symptoms of BV include: 

  • Vaginal discharge (not clear in appearance) 
  • Amine odor (fishy) when the discharge is tested with a chemical 
  • Presence of “clue cells” in a sample of the discharge when examined under a microscope 
  • Lowered acidity of the vaginal discharge 

When a woman exhibits 3 of these 4 symptoms, she’s diagnosed with BV. Fortunately, BV can be cured with a 7-day treatment of prescription antibiotics.