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What is prenatal diagnostic testing?

Prenatal testing includes screening to find problems with a pregnancy as early as possible. Amniocentesis and chorionic villus sampling (CVS) are tests used to analyze fluid or tissue from the mother's uterus. Prenatal testing is also used to diagnose chromosomal disorders such as Down syndrome.

Our approach

The Northwell Health Division of Maternal Fetal Medicine offers a complete line of obstetrical ultrasound and antepartum testing services. The physicians are specialists in obstetrics and gynecology with a subspecialty in maternal fetal medicine. They are accredited by the American Institute of Ultrasound in Medicine and hold a certification for first trimester screening from the Fetal Medicine Foundation.

The team of specialists is committed to providing patients with the highest level of care through superior training and cutting edge technology.

Services are provided by perinatologists, specialists in maternal fetal medicine and diagnostic obstetrical ultrasound, using the latest treatment methods for patients with complicated pregnancies. There is a high risk inpatient unit at our hospitals, specializing in antepartum care for those patients in need of prenatal hospitalization.

Why it's done

Common conditions that require prenatal diagnostic testing include:

  • Uncomplicated pregnancy—All pregnant women are offered various types of prenatal diagnostic testing, such as first trimester screening and obstetrical ultrasound.
  • High-risk pregnancy—Some women may require extra monitoring, care or hospitalization during pregnancy. This may be due to a complication of pregnancy or the woman's own underlying medical needs.
  • Pregnancy complications—There are many different types of pregnancy complications that can affect the mother, baby or both. These complications range from common to rare, and can have a wide variety of causes and effects.

Types of prenatal testing

The following are some common tests performed during pregnancy:

  • Antepartum testing—Antepartum means occurring or existing before birth; antepartum testing refers to various types of tests of fetal well-being, such as biophysical profile. An antepartum testing unit (ATU) is staffed by a team of maternal fetal medicine specialists, nurses, ultrasound technicians and clerical staff.
  • Ultrasound—An ultrasound is a noninvasive diagnostic procedure conducted during your pregnancy to assess your baby’s blood vessels, muscles, organs and development.
  • Amniocentesis—An amniocentesis is a procedure used to obtain an amniotic fluid sample to diagnose chromosomal disorders, genetic defects and other conditions that may be related to your family history.
  • Biophysical profile—A biophysical profile test combines information from an ultrasound and a nonstress test to measure the health of your baby. The test is usually conducted during your last trimester of pregnancy.
  • Chorionic villus sampling—Chorionic villus sampling (CVS) is a prenatal test that takes a sample of placental tissue, which contains the same genetic material as the fetus. Placental tissue can be tested for chromosomal abnormalities and other genetic disorders.
  • Doppler ultrasound—Doppler ultrasound is a type of ultrasound used specifically to measure blood flow in the uterine artery, umbilical cord, fetal brain and other organs. These tests are usually used if your baby is small for your pregnancy stage to see if he or she is receiving enough nutrients from the placenta.
  • First trimester screening—First trimester screenings combine an ultrasound examination and a blood test to determine the risk of certain chromosomal abnormalities. These are typically performed between weeks 11 and 13 of pregnancy.
  • Fetal echocardiogram—A fetal echocardiogram test is a detailed ultrasound using sound waves to create a picture of your baby’s heart structure. Your physician will be able to tell how your baby’s heart is forming and whether or not it is working properly. Women at an increased risk of having a baby with a heart condition are offered an echocardiogram, which is conducted between 18 to 24 weeks of pregnancy.
  • Nonstress testing—Nonstress tests evaluate your baby’s heart rate pattern to make sure the baby is receiving adequate oxygen from the placenta. Nonstress tests are noninvasive and commonly ordered if you are overdue or are having pregnancy complications. They usually last for 20-40 minutes.
  • External cephalic version—External cephalic version is a procedure used when your baby is in the breech position (the buttocks, legs or feet pointing down toward the cervix) or side-lying position, to turn your baby into a head-down position. If your baby is in the breech position, you may have this procedure done before labor begins, typically around 36 to 38 weeks, to make it possible to have a vaginal birth.
  • Percutaneous umbilical blood sampling—Also known as cordocentesis, percutaneous umbilical blood sampling is a test that involves taking a sample of your baby’s blood from the umbilical cord for examination. From the sample, your physician will be able to detect certain genetic disorders, infections, and/or blood conditions. The procedure can also be used to deliver medications to your baby. Percutaneous umbilical blood sampling tests are typically conducted after week 18 of your pregnancy


The risks and side effects of prenatal diagnostic tests vary with each procedure. Some do not have any risks, while others could potentially result in additional complications.

If your physician recommends a prenatal diagnostic test, he or she will walk you through any associated risks and make sure you understand them before proceeding.

How to prepare

In most cases, the test you are receiving requires no preparation at all. If your doctor is scheduling a prenatal diagnostic test, you will be offered clear directions on what kind of preparation is needed – if any.

What to expect after treatment

Depending on what test you receive, it may take a few days for your results to process. In some cases, you may also need to be monitored following the test. Your doctor will give you a complete explanation of what to expect following your appointment and answer any questions you have before proceeding.

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