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Medical Tests During Pregnancy & Their Definitions Part 1

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Pregnancy is a magical time – and one that demands attention. If you’re high risk or your normal prenatal tests have suspicious results, your care provider may begin talking about medical tests with scary, unfamiliar names. To help you understand them, let’s break down some pregnancy medical test definitions.

There are two general categories of pregnancy medical tests, invasive or non-invasive. Follow the links below to read more deeply about each one. Many test for chromosome abnormalities – an extra chromosome is called ‘trisomy’. Trisomies can cause varying degrees of mental and/or physical malformation.

Most women will never have many of these tests. We are offering these definitions in case they are required.


INVASIVE TESTS require going into your body to gather biological samples. They are usually done with a needle inserted into your cervix, vagina, or abdomen.

– Chorionic Villus Sampling (CVS)[1] (core-ee-on-ic vil-us sampling) is an invasive test in which a small part of the placenta is removed to test for chromosomal/genetic conditions like Down syndrome, Tay-Sachs disease, or cystic fibrosis. It cannot test for spina bifida.

CVS is usually done before amniocentesis, between weeks 10-12 of pregnancy. It’s done in two ways – transcervical (through the vagina) or transabdominal (through the abdominal wall).

Risks include miscarriage, rhesus (Rh) sensitization, and infection.

– Amniocentesis [2](am-knee-oh-sen-tee-sis) is an invasive procedure in which a small amount of amniotic fluid is drawn out via a needle inserted through the abdomen into the uterus.

There are two main kinds of amnios – genetic and maturity. Genetic amniocentesis tests for chromosomal conditions like Down syndrome and spina bifida, and is usually done between weeks 15 and 18. If an induction is required before baby is considered term, a maturity amniocentesis will be requested. This is done to determine whether baby’s lungs are developed enough to function after birth.

The risks[3], though small, involve possible miscarriage, leaking amniotic fluid, injury to baby or mom, introducing infection or transferring it from mom to baby, and preterm labor.

– Cordocentesis[4] (cord-o-cen-tee–sis) is done if amniocentesis, CVS, and ultrasound haven’t given clear results. A needle is inserted through the abdomen and uterus to the place where baby’s umbilical cord meets the placenta. A small sample of baby’s cord blood is removed to detect blood conditions and infections, fetal malformations, fetal anemia, and isoimmunisation[5].

The risks[6] include miscarriage, bleeding, slowing baby’s heart rate, and uterine infection.


NON-INVASIVE TESTS are performed without going into mom’s body for biological samples. They are less risky and less traumatic to mom and baby.

– Non-Invasive Prenatal Testing (NIPT)[7], [8] uses a blood sample from mom. It checks fetal DNA for the risk of Down syndrome, extra chromosomes (trisomy 13 or 18) or a sex chromosome abnormality like Turner syndrome. It can also test baby’s sex and rhesus (Rh) blood type.

– Cell-free DNA is done for fetuses at risk for having abnormal number of chromosomes. The test is performed around the tenth week of pregnancy using fetal DNA in mom’s blood.

– Nuchal (nyook-al) Translucency Screen[9] measures the nuchal fold thickness on the back of the fetus’ neck. When a baby has Down syndrome or other genetic problems, this area appears thicker than normal in ultrasound scans.

It’s measured via ultrasound around 10-14 weeks of pregnancy.

Trimester Screens[10] are maternal blood draws done during first and second trimesters. The four main ones are:

  • Combined first trimester screen – blood test plus ultrasound exam. Tests for Down syndrome, Trisomy 13, and Trisomy 18.
  • Second trimester single screen – blood test for neural tube defects.
  • Second trimester triple screen – blood test for Down syndrome, Trisomy 18, & neural tube defects.
  • Second trimester quad screen – blood test for Down syndrome, Trisomy 18, & neural tube defects.

Cervical length measurement[11] is an ultrasound test that measures the length of the cervix in order to prevent pre-term birth. Fifty percent (50%) of women with short cervixes at or before 32 weeks of pregnancy go into preterm labor.

It is done in three ways: transabdominal, transvaginal, and transperineal, after the second trimester.

– Specialized or targeted ultrasound[12] comes in different forms:

  • Specialized ultrasound looks at suspected fetal problems. It uses a more sophisticated machine and can take significantly more time than normal.
  • 3-D ultrasound evaluates baby’s growth, development, facial abnormalities, or neural tube defects.
  • Doppler ultrasound gives information about baby’s circulation.
  • Fetal echocardiography (echo-card-ee-og-ra-fee) gives images of baby’s heart to confirm or rule out heart defects.

– Prenatal lab work and tests[13] are routine tests many women get to detect conditions that may cause increased risk to you or your baby. They are done at the first prenatal exam and usually include:

  • Complete blood count (CBC)
  • Blood type for Rh factor
  • Urinalysis
  • Rubella
  • Hepatitis B & C
  • Sexually transmitted diseases (STDs)
  • Vitamin D
  • Human immunodeficiency virus (HIV)

– Biophysical (by-o-fizz-i-cal) profile[14] checks to see how baby’s doing in the last trimester of pregnancy. It tests fetal heart rate, breathing, movements, muscle tone, and amniotic fluid level.


Even a basic understanding of the tests and how to pronounce them empowers you to ask informed questions. The more you understand, the better your care provider can work with you. The better your communication with your care provider, the better birth plan you can write – make sure it’s on your hospital bag checklist!




To learn more about taking care of yourself during pregnancy, download our free Birth Plan eBook now. After three years of research, collaboration with more than 100 childbirth experts and resource centers from Healthy Child Healthy World to the American Association of Neonatal Nurses, the Best Ever Baby Birth Plan Guide is available for a free download.

This new resource for pregnant families is a compilation of top tips and advice from more than 20 nationally-recognized experts in the field including renowned pediatrician, Dr. Alan Greene and GraceFull Birthing founder, midwife Elizabeth Bachner.  These trusted experts offer thoughtful guidance for whatever type of birthing experience parents want, in whichever setting they choose.


Published: September 6, 2015 | Reviewed by: Kim Walls, Natural Products Expert, Elizabeth Bachner, LM, CPM, L.Ac., Midwife | Last reviewed: September, 2015

Kim WallsMedical Tests During Pregnancy & Their Definitions Part 1

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