During the first trimester, your healthcare provider will present you with many options for medical and genetic testing. All moms-to-be should have their blood drawn and urine tested, but those with increased risk factors for genetic conditions (including a family history of chromosomal disorder or being 35 years of age or older on your due date) may be advised to undergo further tests. Typical medical tests ordered during the first trimester include the following, although not all women will need or choose all of these options.
At your very first prenatal appointment, your healthcare provider will usually have your blood drawn and tested for a number of factors, including blood type, red blood cell count, Hepatitis B, HIV, Rh-factor, syphilis and rubella.
Your healthcare provider will do this to make sure you do not have a disease or deficiency that could affect you or your pregnancy. In the case of the Rh-factor, they will make sure that your immune system does not identify the fetus’ blood cells as foreign bodies, as it does for viruses and bacteria. Just about all women will have their blood tested at the first prenatal visit.
Urine tests are going to be a staple of each prenatal appointment, as your healthcare provider will ask you to provide a urine sample each time. Your healthcare provider will check your urine for the elevated presence of either protein or sugar, both of which can indicate serious pregnancy-related conditions like preeclampsia or gestational diabetes.
Chorionic villus sampling
Chorionic villus sampling (CVS) is an invasive diagnostic procedure that can obtain cells to help detect chromosomal defects in your pregnancy. Women who have a family history of chromosomal disorders or are over 35 years of age on their due date are typically offered CVS, but most do not need it unless their first trimester screen showed any risk. The chorionic villus sampling includes taking placental cells (containing the same genetic material as baby’s cells) and testing the cells for chromosomal disorders, and is most commonly performed between weeks 10 and 13 of pregnancy.
First trimester combined screen
Performed between weeks 11 and 14 of pregnancy, the First Trimester Combined Screen is a testing option that consists of a maternal serum screening mest (MSS) and a Nuchal Translucency (NT) ultrasound examination.
The MSS tests for pregnancy-associated plasma protein-A (PAPP-A) and human chorionic gonadotropin (hCG) – abnormal levels of both can indicate a chromosomal disorder. In addition, the NT ultrasound is performed to determine the size of clear space (fluid) in the back of the unborn baby’s neck, which can also indicate elevated chances of Trisomy 21 (Down syndrome), or other developmental conditions. The First Trimester Combined Screen is not diagnostic, it merely screens for an increased likelihood of having certain chromosomal disorders. Although it identifies ~85% of unborn babies with Down syndrome, 5% of those tested will also register a false positive result.
Because Down syndrome is relatively rare, the majority of pregnant women who get a positive Combined Screen test result will deliver a baby without Down Syndrome. The First Trimester Combined Screen is highly effective at screening for chromosomal disorders – it provides the odds of your unborn baby having a disorder (e.g., 1/1000) rather than conclusive results for the genetic disorders.
Cell-free fetal DNA testing
This test is indicated as early as week 10 of pregnancy and is a highly accurate way of assessing for chromosomal fetal abnormalities (abnormal number of chromosomes). The screening analyzes pieces of chromosomes that originate from the cells of the placenta to determine if your unborn baby might have any chromosomal abnormalities. This test is a great way to look for the possibility of a chromosomal disorder without the risk of miscarriage.
- Amy Swanson, Amy J. Sehnert, Sucheta Bhatt. “Non-invasive Prenatal Testing: Technologies, Clinical Assays and Implementation Strategies for Women’s Healthcare Practitioners.” Curr Genet Med Rep. 1(2): 113-121. Web. 6/13/2015.
- Mayo Clinic Staff. “Prenatal care: 1st trimester visits.” Mayo Clinic. Mayo Clinic, 7/31/2015. Web.
- “Prenatal care in your first trimester.” U.S National Library of Medicine. MedlinePlus, 6/11/2014. Web.
- “Prenatal tests.” March of Dimes. March of Dimes, 6/3/2016. Web.
- Mayo Clinic Staff. “Chorionic Villus Sampling.” Mayo Clinic. Mayo Clinic, 10/17/2015. Web.
- Mayo Clinic Staff. “Noninvasive prenatal testing.” Mayo Clinic. Mayo Clinic, 2/23/2013. Web.