Health care providers conduct pregnancy tests to ensure proper fetal health and to detect any issues. Early detection will help optimize the baby’s health and development. For pregnancy tests, the doctor may recommend several types of screenings, blood tests, and imaging techniques.
Some of the Common Tests conducted during pregnancy are:
1. Prenatal screening tests in the first trimester
The first trimester of pregnancy has a combination of tests consisting of maternal blood testing and fetal ultrasound. This is conducted to help to detect any congenital disabilities or risks that the fetus may have. The screening tests can be divided into three parts –
2. Ultrasound test for Nuchal translucency
Nuchal translucency screening using an ultrasound test ensures no extra fluid or thickening in the area behind the fetal neck.
3. Ultrasound for determination of fetal nasal bone
The nasal bone of babies who have chromosome abnormalities cannot be visualized. An Ultrasound is conducted between 11- 13 weeks’ gestation.
4. Maternal serum/blood tests
These tests are conducted to measure two contents found in the blood of all pregnant women.
5. Human Chorionic gonadotropin (hCG)
An abnormal rise in the levels of this hormone is linked to the risk of a chromosome problem.
6. Pregnancy-associated plasma protein screening (PAPP-A)
This is a protein made in the early stages of pregnancy in the placenta. An abnormal increase of this protein is also linked to chromosome problems.
When these tests are conducted together, you determine any congenital disabilities in the fetus, for instance, down syndrome.
If the results in the first trimester show any abnormality, then genetic counseling is recommended by the health care specialist. Additional tests like cell-free fetal DNA, chorionic villus sampling, and ultrasounds might be guided by a doctor if he deemed necessary.
common pregnancy test during Second trimester
Second-trimester screening includes several blood tests. These are known as multiple markers. This gives information about any genetic conditions or birth detects which the fetal may have. Screening is typically done by taking a sample of blood between the 15th and 20th weeks of pregnancy. The 16th and 18th are considered ideal.
The markers are explained below:
1. Alpha-fetoprotein screening (AFP)
This test is conducted to measure the levels of alpha-fetoprotein in the blood of pregnant women. It is a protein that is typically made in the fetal liver. It is the fluid around the fetus (amniotic fluid) and crosses the placenta into the blood. The other name for the alpha-fetoprotein blood test is MSAFP (maternal serum AFP). Abnormal levels of AFP may mean-
- Incorrect due date
- Issues in the abdominal wall of the fetus
- Down Syndrome
- Open neural tube defects, for instance, spina bifida
- Other chromosome issues
2. Other makers
- hCG: The human chorionic gonadotropin hormone
The placenta produces all the hormones mentioned above.
Atypical results of AFP and other markers mean more testing is required. Followed by this, an ultrasound is performed in order to confirm the dates regarding pregnancy. An ultrasound is also helpful to look at the fetal spine as well as other body parts. However, amniocentesis is required for a more accurate diagnosis.
Multiple markers are not 100% accurate but are performed to determine the need for more testing. This means. If the tests show that the fetus is healthy, then more tests might not be advised, but if the doctor suspects any problems, they would ask you to take other tests to make a 100% diagnosis.
The false-positive test result means the fetus is healthy, and a false negative test result indicates a health issue.
The first and second-trimester screening can detect 19 out of 20 cases of down syndrome. The likeliness of catching a problem increases when both the tests are conducted rather than a single first-trimester screening.
Some brief on the tests conducted during pregnancy
An ultrasound is a test in which high-frequency sound waves are used to make the image of the internal organs. During pregnancy, it is conducted to monitor fetal growth and to estimate the due date. An ultrasound is performed numerous times in the course of pregnancy for numerous reasons.
In the first trimester, ultrasound is conducted to –
- To estimate the due date as ultrasound provides an accurate due date
- To monitor uterus and another pelvic anatomy
- To diagnose any possible miscarriages or ectopic pregnancy
- To determine the number of fetuses and monitor the placenta
- To detect any fetal problems
Mid-trimester (the 18- to 20-week scan)
- To confirm the set due date
- To monitor the placenta and check the number of fetuses
- To monitor blood flow patterns
- To monitor fetal movements and behaviour
- To check the fetal anatomy to determine the fetal growth is normal
- To monitor the levels of amniotic fluid
- To measure the length of the cervix
- To assist the prenatal tests such as amniocentesis
In the trimester, ultrasound is conducted to –
- To check the fetal growth is normal or abnormal
- To determine the levels of amniotic fluid
- To monitor the placenta
- To determine the position of the fetal
- To complete a biophysical profile
Types of ultrasound
1. Abdominal ultrasound
In this, the healthcare specialist applies gel on the abdominal area and glides the ultrasound transducer over to get an image.
2. Transvaginal ultrasound
In this, the healthcare specialist uses a more miniature ultrasound transducer. The transducer is placed inside the vagina and rests it against the back to create an image. This process allows getting a sharper image. This type of ultrasound is typically used in the starting months of the pregnancy.
Ultrasound is conducted in three ways in 2D, 3D, and 4D imaging. The most common is 2D, but this gives a flat picture of one aspect of the image. The 3D image shows the width, height, and depth of the images. This is helpful when the healthcare specialist requires more information, but this ultrasound requires a particular machine and special training. In a 4D, the fetus can be seen moving in real-time. You can store ultrasound images in still photographs or in the video to document.
Ultrasound gives the parents the way through which they can see their baby prior to birth. This helps to develop the bond between them and establish the relationship.
Risks of an ultrasound
There are no such risks associated with ultrasound other than some mild discomfort. This may be due to the transducer on the abdomen or in the vagina. This procedure does not use any radiation.
Genetic carrier screening
This is a screening process that is conducted to diagnose any genetic problems before birth. A doctor may recommend such a test if you or your partner have a family history of genetic disorders or if they suspect the fetus to have a genetic problem.
Genetic disorders which are commonly screened for are –
- Cystic fibrosis
- Fragile X
- Spina muscular dystrophy
- Tay-Sachs disease
- Sickle cell anemia
It is a test conducted by placing a long thin needle through the abdomen into the amniotic sac. The sample of the amniotic fluid is taken, and this sample contains the cells shed by the fetus, which has and provides genetic information. This is conducted to diagnose chromosome-related problems and open tube defects. This test can also detect other genetic disorders. This test is usually performed between the 15th and the 20th week of pregnancy.
If you are carrying twins, individual sampling from each amniotic sac is needed to study each baby. This is often advised to be free from any strenuous activity for 24 hours after this test has been conducted. The results are typically provided within 10 to 14 days.
In some cases, amniocentesis cannot be conducted depending on the position of the baby, amniotic fluid, anatomy, etc. Therefore, to knows the risks, and please consult with your health care provider to learn more.
2. Chorionic villus sampling (CVS)
Chorionic villus sampling (CVS) is a prenatal test conducted to detect any chromosome problems. Unlike amniocentesis, this cannot detect open neural tube defects, as a reason women who have had CVS are suggested to take a blood test between 16 to 18 weeks of their pregnancy to screen for open neural tube defects. This test involves taking a sample of the placental tissue. This tissue contains the genetic material of the fetus.
This test is recommended for those with a family history of genetic problems. This test is conducted between the 10th and the 13th week of pregnancy.
This test is conducted by placing a small tube (catheter) through the vagina into the cervix and taking the tissue sample with the help of the syringe, which is on the end of the catheter. For a transabdominal CVS, the provider puts a needle through the abdomen into the uterus to take the sample of the placental cells. This process is not always advisable for those carrying twins.
3. Fetal monitoring
In the event of late pregnancy and active labor, your doctor might want to monitor fetal heart rate and other functions. Fetal monitoring is a process to check the heart rate and rhythm of the baby. The average heartbeats per minute are about 110 to 160 beats. However, this may change depending on the conditions in the uterus. An abnormal fetal heart rate means that the fetus is not getting the required oxygen, which may indicate a cesarean delivery.
This type of monitoring is carried out by a type stethoscope called a fetoscope or a handheld Doppler device.
4. Glucose tolerance tests and glucose challenge
First, a glucose challenge is taken, and if the results are abnormal, then a glucose tolerance test is taken. These are conducted at 24 to 28 weeks’ pregnancy to measure the levels of glucose in the blood. Abnormal levels mean gestational diabetes. The test is done if you have an elevated 1-hour glucose challenge test. In this, the specialist will ask you to intake only water and then takes a fasting sample of blood. After that, they provide a glucose drink. After this, the blood will be drawn several times again over several hours to measure the glucose levels in the body.
5. Group B strep culture
GBS is one the most common cause of life-threatening infections in newborns, including pneumonia and meningitis. Newborns get this from the mother’s genital tract during labour and birth. The Group B streptococcus is a bacteria found in the lower genital tract in about 1 of out 4 women. GBS may cause chorioamnionitis, which is a severe infection of the placental tissues. Urinary tract infections can cause premature birth and labour or sepsis etc. This test needs to be taken between 35 to 37 weeks of pregnancy.
Tests play an essential part in saving you and your baby from various genetic and non-genetic problems. These not only ensure safer pregnancy but will also help have a healthier baby. Early detection will also help cure and take steps that are essential to your pregnancy.