Pregnancy & Prenatal Testing

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Overview

Pregnant Woman reads brochure on pregnancyPregnancy is the period of time when a fetus develops inside a woman’s uterus and ends with the birth of the infant. Pregnancies typically involve a variety of clinical laboratory tests. The tests provide useful information from the time pregnancy is first considered through the initial days of the newborn's life. Some of these tests are performed at specified times throughout the pregnancy. Others are ordered as needed to detect and address conditions or problems that arise during pregnancy. Still others are offered to women who have increased risks because of their age or lifestyle and, finally, certain tests are selectively chosen based on the personal and family medical histories of the woman and her partner.

The purposes of prenatal tests are to screen for and diagnose any existing problems that may affect the mother's or baby's health, identify and address problems as they arise, and assess the risk of a baby having a chromosomal or genetic abnormality. The tests generally require just a small sample of easily obtained blood, urine, or cervical cells.

The following pages contain information on many of these routine and some less routine tests. Your health care provider may recommend additional tests based on your medical history. Parents-to-be are encouraged to ask their health care providers why specific tests are being offered to them. Health care providers and reliable Internet sources, such as the March of Dimes and the U.S. Centers for Disease Control and Prevention, can help you understand the risks and benefits of each test.

Below is a table summarizing these tests:

Screening Tests During Pregnancy

Health care providers and reliable medical sources, such as the March of Dimes and the U.S. Centers for Disease Control and Prevention, can help you understand the risks and benefits of each test.
Purpose Test name Why performed When performed Who performed on/Sample
Genetic tests for inherited diseases Genetic testing for inherited diseases Check carrier status for certain genetic diseases to determine risk of having a baby with such a disease Pre-conception or first trimester Mother and father (blood sample)
Genetic testing for hemoglobin disorders Check carrier status for certain hemoglobin disorders to determine risk of having a baby with such a disease Pre-conception or during pregnancy Mother and father (blood sample)
Cystic fibrosis carrier testing Check carrier status for CF Pre-conception or first trimester Mother and father (blood sample)
Testing associated with health conditions of the mother that affect pregnancy Immunity to rubella (German measles) Check for immunity to the virus, which can cause birth defects Pre-conception or first trimester Mother (blood sample)
Human immunodeficiency virus (HIV) antibody test Check for HIV infection so steps can be taken to reduce likelihood of transmission to the baby Pre-conception or first trimester; may be repeated in third trimester if at high risk Mother (blood sample)
Gonorrhea, chlamydia, and syphilis tests Check for STD infections, which can cause miscarriage or infect the baby during delivery Pre-conception or first trimester; may be repeated in third trimester if at high risk Mother (cervical cells, urine or blood sample, depending on test)
Pap smear Detect abnormal cervical cells, inflammation, or STDs Pre-conception or first trimester Mother (cells from her cervicx)
Hepatitis B screening Detect Hepatitis B infection Pre-conception or first trimester; may be repeated in the third trimester if at high risk Mother (blood sample)
Varicella zoster viral testing Check for immunity to chicken pox, which can cause birth defects Pre-conception or first trimester
Mother (blood sample)
TORCH panel Check for infection with toxoplasmosis and other infectious diseases that can cause birth defects Pre-conception or first trimester, if infections suspected Mother (blood sample)
Bacterial vaginosis Detect infection, which can cause pre-term labor and birth Pre-conception or whenever symptoms experienced Mother (vaginal secretions)
Urine culture for bacteriuria Detect bacterial infection in the urinary tract, which can lead to kidney infection or increased risk of pre-term delivery and low birth weight First prenatal visit or between 12 and 16 weeks of pregnancy; may be repeated in third trimester Mother (urine sample)
Group B streptococcus Detect infection, which can harm the baby during birth and infect the mother’s uterus, urinary tract, and any incision made during a cesarean section Between weeks 35 and 37 of pregnancy Mother (specimen from vaginal and rectal areas)
Monitoring of pregnancy Pregnancy test Confirm pregnancy First trimester Mother (blood sample)
Urine screen for sugar and/or protein Check for signs of kidney or bladder infection, undiagnosed diabetes or gestational diabetes, or preeclampsia Each prenatal visit Mother (urine sample)
Hemoglobin test Check for anemia Pre-conception and/or early in the first trimester; repeated in third trimester Mother (blood sample)
Antibody screen Check for potential incompatibility in blood type between mother and fetus (such as Rh factor antibodies) First trimester; repeated at week 28 of pregnancy Mother (blood sample)
Glucose challenge test/oral glucose tolerance test Check for gestational diabetes Between 24 and 28 weeks of pregnancy Mother (blood sample)
Platelet count Detect a low count or other platelet problem; platelets are important for blood clotting in case of bleeding during delivery Third trimester Mother (blood sample)
Detection of fetal abnormalities or risk First trimester Down syndrome screen Assess risk of carrying a fetus with certain chromosomal abnormalities, such as Down syndrome Usually between 10 weeks, 4 days and 13 weeks, 6 days of pregnancy Mother (blood sample plus ultrasound)
Triple marker or quad marker screen Assess risk of carrying a fetus with certain chromosomal abnormalities and open neural tube defects Between 15 and 20 weeks of pregnancy Mother (blood sample)
Chorionic villus sampling Detect chromosomal disorders in the fetus Between weeks 10 and 12 of pregnancy, if recommended Mother (cells from the placenta)
Amniocentesis Detect certain birth defects and chromosomal abnormalities Between 15 and 20 weeks of pregnancy, if recommended Mother (amniotic fluid)
Cordocentesis Detect chromosome abnormalities, blood disorders, and certain infections Between weeks 18 and 22 of pregnancy, if recommended Mother/fetus (fetal blood sample obtained from vein in the umbilical cord)
Fetal maturity/readiness for birth Amniocentesis Check fetal lung development After week 32 of pregnancy if risk of pre-term delivery Mother (amniotic fluid)
Fetal fibronectin (fFN) Detect fFN, negative result is highly predictive that pre-term delivery will NOT occur in the next 7-14 days Between week 26 and 34 of pregnancy, if having symptoms Mother (cervical or vaginal fluid sample)