Common Screening Tests During Pregnancy
Discuss the most common screening test and diagnostics used throughout pregnancy and the purpose of the tests. When during pregnancy are tests performed and what is the protocol when an abnormal test or diagnostic is found?
Health care provider may recommend a variety of screenings, tests and imaging techniques during a pregnancy. These tests are designed to provide information about the health of your baby and may help you optimize your child’s prenatal care and development (American Pregnancy Association, 2018). Genetic screening can help diagnose the potential for certain genetic disorders before birth. First-trimester screening is a combination of fetal ultrasound and maternal blood testing. This screening process can help determine the risk of the fetus having certain birth defects. Second trimester prenatal screening may include several blood tests called multiple markers. These markers provide information about the risk of having a baby with certain genetic conditions or birth defects. The ultrasounds can be performed at different times during the pregnancy to check for fetal growth, estimate the due date and look for any structural abnormalities in the baby. Additional testing during pregnancy may include amniocentesis, chronic villus, sample (CVS) and fetal monitoring glucose testing and Group B strep culture. Many genetic abnormalities can be diagnosed before birth (American Pregnancy Association, 2018) . Therefore, the PCP or midwife may recommend genetic testing during pregnancy in case there is a family history of genetic disorders. other reason may also be to have genetic screening when the fetus or baby has a genetic abnormality.
Depending on the situation if an abnormal screening test comes the patient should be aware of and counsel the risk of having the baby and the percentage of survival of the fetus. It will be up to the parents of the unborn child to decide whether they should continue with the pregnancy. I have seen a patient who was advised to end the pregnancy because of the high risk of the death of the mother. depending on the situation, some parents may choose to abort the baby. for example, this who recently found that she was 8—9 weeks pregnant via ultrasound for the fifth time, the patient who had 3 c sections 4 living children and was pregnant for the fifth her last baby was 10 months old. The physician had to explain the high risk of having a hysterectomy right after given birth and risk of bleeding to death.
Pregnancy is a cascade of miracles occurring one after another. The development of a growing embryo to a fetus to a full-term infant involves constant replication of cells and therefore any delivery of a healthy baby is truly a miracle. Gestation typically last 40 weeks and is broken down into trimesters (i.e. 1st – 0-12 weeks, 2nd – 13-28 weeks, 3rd – 29 weeks to delivery). Women typically request pregnancy testing, either at home or at their primary care provider’s office, when they have either missed a menstrual cycle or are having symptoms of pregnancy (i.e. nausea, breast tenderness, etc.). These tests are designed to measure human chorionic gonadotropin (HCG), which is a hormone secreted by the placenta once a fertilized egg implants within the uterine lining (Mayo Clinic, 2018).
Because pregnancy is not a benign condition, many screening tests can be completed in order to identify any potential issues with the growing fetus (i.e. birth defects, low weight, etc.) at the earliest possible stage.
During the first trimester, the following tests can be ordered:
- Maternal blood screen to test for HCG and pregnancy associated plasma protein A (PAPP-A). If either of these results are elevated, there can be an increased probability for chromosomal disorders. Blood typing also occurs at this time and if the mother is RH negative will need a Rhogam injection at 28 weeks and immediately after childbirth.
- Ultrasound in the first trimester can be used to look for anomalies such as fluid behind the fetus’ neck or presence of a nasal bone and is considered the most accurate method to determine estimated delivery date (EDD). These two screening methods can accurately provide evidence of Trisomy 18 or 21 (Down Syndrome) (John Hopkins Medicine, 2016).
During the second trimester the following tests can be ordered:
- Between 15-20 weeks, a Quad screen tests for the presence of 4 proteins (alpha-fetoprotein (AFP), HCG, Estriol and Inhibin-A.
- Between 18-20 weeks, an anomaly ultrasound can be completed to determine size of the fetus and identification of any birth defects (Centers for Disease Control and Prevention, 2017).
During the third trimester, the following tests can be ordered:
- Oral glucose tolerance test (OGGT) to determine whether the patient has developed gestational diabetes (GDM) can be completed during the 24-28 weeks. If found to have GDM, patient will need to be educated on diet changes and potentially get started on metformin.
- Group beta strep (GBS) can be tested for during the 35-37 weeks. If positive, IV antibiotics will need to be administered prior to delivery of the child.
- Tdap for anyone who will be in contact with the infant to protect against pertussis and the influenza vaccine to protect against influenza.
If any of the genetic testing results in an anomaly, further diagnostic testing can take place. These types of additional testing include amniocentesis and chorionic villus sampling (CVS) and can help differentiate between the exact genetic anomaly exists (Centers for Disease Control and Prevention, 2017).