Which tests are necessary?

Your care provider may order or suggest various tests during the course of your pregnancy.

It is important to understand what type of information these tests supply, allowing you to make an informed decision about whether all are necessary and what you will do to address the information they provide.

First Trimester Lab work

During the first trimester your care provider will probably order a test called a prenatal panel or OB panel which includes tests like these:

CBCD – will tell if you are anemic and if you have an adequate level of platelets. it also shows if there is a current infection.

ABO, Rh factor, and Antibody screen – This test will tell what your blood type is and your Rh factor, the antibody screen shows if there has been any mixing of blood in the past causing you to become “sensitized” These tests will tell whether you need a roam shot or not during your pregnancy and after the baby is born.

Hepatitis B surface antigen – to see if you are negative or immune

Rubella – If you are immune, then you have nothing to worry about, if you are not immune, then you want to stay alert and if you hear that someone has German measles, then don’t expose yourself to that person during your pregnancy.  Rubella is most dangerous to your baby if you catch it during the first 20 weeks of pregnancy. It can cause miscarriage, stillbirth or birth defects in unborn babies, such as: hearing loss or brain damage.

RPR or VDRL – tests for syphilis

HIV 1 and 2 – these are the two most common types of HIV and it is routine to test all pregnant women for them early in pregnancy and sometimes again late in pregnancy.

Other blood tests that may be ordered include, but are not limited to:

TSH and Free T4 – checks for hypothyroidism

Vitamin D 25, hydroxy– checks your Vitamin D3 level

Hemoglobin A1c – tells what your average blood sugar has been for the past three months. This may be done if you are at risk of developing gestational diabetes.

Comprehensive Metabolic Panel –  is a group of blood tests. They provide an overall picture of your body’s chemical balance and metabolism.

MTHFR MutationIt may be that 1 in 4 women may have this mutation, which can cause elevated homosysteine levels and can contribute to blood clots. High homocysteine can also cause pre-eclampsia and miscarriage. This is a complex problem that you will need to talk with your health care provider about.

Urine Tests

Urine dip stick often done at every visit. This can be done in the office and checks for protein and glucose in the urine.

Urinalysis to check for infection and if one is found a culture may be done as well.

Chlamydia and Gonorrhea – these may be done as a urine test or a culture. If the test is negative, then you don’t need to use antibiotic eye ointment in the babies eyes at the time of birth. If the test is positive, then the baby could pick up the infection coming through the birth canal and if untreated it could lead to blindness.

Cystic Fibrosis- Even when there is no family history of the disorder, the American College of Obstetricians and Gynecologists (ACOG) recommends that all couples planning a pregnancy or having their first visit for prenatal care be offered a carrier screening test for cystic fibrosis (CF).

Because individuals with CF inherit one CFTR gene from their mother and one from their father, for CF to present, both CFTR genes must be abnormal.  If  the mother carries a CFTR mutation, then the father’s blood will be tested. If he is also a carrier of a CFTR mutation, then the baby has a 25 percent chance of having cystic fibrosis.

Second and Third Trimester

Pap Smear – check for cervical cancer and may be done during pregnancy if she is not up to date

At 24 to 28 weeks it is common to test for Gestational Diabetes

At 35 – 37 weeks the GBS culture is done and some providers may repeat the CBCD and HIV, and do a late ultrasound as well.


With an ultrasound, reflected sound waves are electronically processed to create an image of your developing baby, similar to the technology used by radar, but at much lower power levels.ultrsound

Ultrasound can be a valuable tool, helping the trained technician and physician to identify potential health problems or physical defects, allowing them to initiate corrective procedures or be better prepared for complications at the time of birth.

Many healthy pregnant women who do not have risk factors may choose to limit the number of ultrasounds they get during their pregnancy. The 20 week anatomy screen may be the only one they get. See references below about the safety of Ultrasounds, this is something that we don’t want to take lightly, while they are a great tool it may not be a good idea to over use them especially the early ones.

When the last menstrual period is not known or if more than one baby is suspected or if there is bleeding during pregnancy, then it may be necessary to do an ultrasound earlier in pregnancy or more often.

Weighing the risks and benefits of routine ultrasound

The evidence does not prove that a single ultrasound scan at relatively low intensity performed by a skilled operator will cause harm to a developing baby.

However, there is sufficient evidence that multiple pulsed ultrasound scans, or as few as two continuous wave Doppler scans, or any ultrasound scan performed by an unskilled operator may cause harm.  Large epidemiological studies need to be performed using the higher ultrasound intensities commonly used today.

When making a decision to perform any medical diagnostic test or procedure, benefits must always be weighed against risks. It’s rarely a black or white issue.

There are now direct-to-consumer ultrasound services which bypass the physician, simply for the expectant mother or parents to take monthly “snapshots,” or to establish the sex of their developing child. However because the possible long-term effects of ultrasound are still an unknown, a more cautious approach would be to use ultrasound only when medically necessary. It is also important to recognize that these consumer ultrasound services do not provide the information that your care provider needs to know and are not a substitute for the anatomy screen.

Testing for Birth Defects

Testing for birth defects can be a very personal decision. There are many angles to consider. Some women choose not to get these tests done because they do not plan to discontinue their pregnancy if a problem is found.

Other parents-to-be might feel like they want to know even if they don’t plan to end the pregnancy. They might want to know so they could join a parent support group or be more educated about what to expect or how to care for their special needs child.

Some defects can be repaired during the pregnancy if found in time. One example is twin-to-twin transfusion and could be life saving for one of the twins. Another example is Congenital diaphragmatic hernia or some types of congenital heart disease.

If there are known risk factors for the pregnancy, if she has had multiple losses with the same partner in the past, or if she would end the life of a fetus that has a defect that is not compatible with life; then testing may be something she wants to do.

Screening vs Diagnostic Tests – Screening tests are not 100% accurate and some have a higher % of false positives than others. If you test positive, then the next step is to get a diagnostic test. The diagnostic test has a higher accuracy rate, however diagnostic tests are more invasive. Examples of diagnostic tests are Amniocentesis and CVS. both of these tests carry a risk of miscarriage, so if you do not plan on ending the pregnancy or doing fetal surgery, then you may not want to take the risk.

If knowing that your baby may have special needs ahead of time is important to you so you can become informed, then you may want to do these tests. It is a very personal decision that only you can make.

Non Invasive Prenatal Test (NIPT)

There are some cells from the baby that float around in the mother’s blood stream. After the 9th week of pregnancy, a sample of blood taken from the mother can be tested for the most common birth defects: trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome), and trisomy 13 (Patau syndrome). The NIPT has fewer false positives than some of the other blood tests done in the past and is 99% accurate. Since this test is not invasive, many pregnant women feel better getting this test if they have risk factors due to family history, age, previous loss, etc.

NIPT also detects your baby’s Rh blood type and gender, so be sure to let your midwife know if you are not planning on finding out the sex of your baby!


Amniocentesis is a diagnostic test that detects chromosome abnormalities, neural tube defects and genetic disorders with high levels of accuracy (98-99%). Although the probabilities of identification are high, this test does not measure the severity of these birth defects. It is an invasive procedure in which a needle is inserted through the abdomen to draw amniotic fluid surrounding the baby from inside the water bag.

Risks include:

  • A 0.6% chance the amniocentesis will cause a miscarriage.
  • The needle used for the procedure may come in contact with the developing fetus.

Before agreeing to tests which require amniocentesis, you should consider how you will this information. For example, if tests reveal a possibility of a baby with Downs Syndrome, will you terminate the pregnancy?

If the answer is NO, consider if the information will cause you stress or what will you do with the information?

CVS – Chorionic Villus Sampling is done to test for any chromosomal abnormalities. Since the Chorionic villi (tiny finger like units in the placenta) have the same chromosomal makeup of the fetus, this can be tested my extracting some and checking its chromosomal structure. Although this test is extremely accurate, there are risks including; a 1% risk of miscarriage, infection, spotting or bleeding, and birth defects if done to early. A doctor may recommend this test if you are older that 35, have a history of genetic disorders, have a previous child with a disorder, show signs of concern from another test

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Natural childbirth IIb: ultrasound not as safe as commonly thought by Chris Kresser  https://chriskresser.com/natural-childbirth-iib-ultrasound-not-as-safe-as-commonly-thought/

Next: Complications During Pregnancy

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