2.9: Prenatal Assessment
- Page ID
- 204947
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)A number of assessments are suggested to pregnant individuals as part of their routine prenatal care to find conditions that may increase the risk of complications for the pregnant individual and fetus (Eisenberg, Murkoff, & Hathaway, 1996). These can include blood and urine analyses and screening and diagnostic tests for birth defects.
There are screenings like AFP blood tests that can screen for the possibility or likelihood of certain problems with the pregnancy or fetus. When these screens suggest an increased likelihood, they might warrant further testing or treatment.
Ultrasound
Ultrasound is one of the main screening tests done in combination with blood tests. The ultrasound is a test in which sound waves are used to examine the fetus. There are two general types. Transvaginal ultrasounds are used in early pregnancy, while transabdominal ultrasounds are more common and used after 10 weeks of pregnancy (typically, 16 to 20 weeks).
Ultrasounds are used to check the fetus for defects or problems. It can also find out the age of the fetus, location of the placenta, fetal position, movement, breathing and heart rate, amount of amniotic fluid in the uterus, and number of fetuses. Most people have at least one ultrasound during pregnancy, but if problems are noted, additional ultrasounds may be recommended.
Amniocentesis
When diagnosis of a birth defect is necessary, ultrasounds help guide the more invasive diagnostic tests of amniocentesis and chorionic villus sampling. Amniocentesis is a procedure in which a needle is used to withdraw a small amount of amniotic fluid and cells from the sac surrounding the fetus and later tested.
CVS
Chorionic Villus Sampling is a procedure in which a small sample of cells is taken from the placenta and tested. The steps of the procedure are very similar to the amniocentesis. What is different is that a CVT is done earlier in pregnancy. Both amniocentesis and chorionic villus sampling have a risk of miscarriage, and consequently they are not done routinely.[3]
Blood and Urine tests
At every prenatal visit the pregnant individual's urine is usually tested for diabetes, urinary tract infections and preeclampsia. Blood tests measure different types of chromosomal abnormalities when done at specific times during pregnancy. They are also used in conjunction with drinking a sugary drink in order to test for gestational diabetes.
In the last decade or so, blood tests have also been used to test for fetal DNA that might indicate issues like Down Syndrome. More recently there are tests being developed to screen for maternal, placental and fetal RNA to see whether there is an increased risk of preeclampsia and preterm births (Kwon, 2023).
Biophysical Profile and non-stress tests
A belt is placed around the pregnant abdomen during the third trimester and the fetal heartbeat is monitored to see if the fetus is getting enough oxygen. The movement, muscle tone and level of amniotic fluid also tells physicians about the health of the fetus.
Why test?
As you might note the tests described above range in their invasiveness. Blood and urine tests, and ultrasounds are very non-invasive and hence are routinely performed to screen for (and in some cases to diagnose) potential problems. However, some tests are much more invasive. The CVT and amniocentesis include more invasive techniques and are usually done only when there is reason to suspect something - for example, advanced maternal age, a positive screen or family history of a genetic condition.
References:
Kwon, D. (2023). New noninvasive RNA tests could help identify at-risk pregnancies. Knowable Magazine from Annual Reviews. doi: 10.1146/knowable-081623-1
Attributions:
Child Growth and Development by Jennifer Paris, Antoinette Ricardo, and Dawn Rymond, 2019, is licensed under CC BY 4.0
[1] Image by MedicalPrudens is licensed under CC0 1.0
[2] Image by BruceBlaus is licensed under CC BY-SA 4.0
[3] Lifespan Development: A Psychological Perspective by Martha Lally and Suzanne Valentine-French is licensed under CC BY-NC-SA 3.0
What tests might I need during pregnancy by NIH, in the public domain