Many pregnant people describe the second trimester as a time when nausea decreases and energy increases. These are welcome changes, especially if the first trimester was difficult. And for expectant parents who previously experienced a first trimester loss, making it to the second trimester can feel reassuring and might even mean less stress and anxiety.

Pregnant person having an ultrasound - What you need to know about second trimester testing and screening

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Of course, that’s not true for all who are pregnant after loss, and it’s completely normal to continue having a wide variety of feelings. During the second trimester, there are a few screenings and tests that might give you peace of mind as you learn more about your growing baby[1]“Prenatal Tests: Second Trimester,” reviewed by Armando Fuentes, MD, Kids Health from Nemours, Much like first trimester screenings and tests, though, some parents find these tests to be nerve-wracking.

Before you decide which tests to undergo, it’s important to understand what they’re looking for. Here are the four most common second trimester tests and why you might need them.

Genetic Screening

Between 15 and 20 weeks of pregnancy, your provider will give you the option to have genetic screening if you haven’t already had it in the first trimester. This round of blood tests in the second trimester goes by different names. The broad term is multiple marker screening, and depending on how many substances the screening is examining, you may hear it called the “triple screen” or the “quad screen.”

The ideal time for the multiple marker test is between 16-18 weeks, and it screens for Down Syndrome, Edwards Syndrome (trisomy 18), and neural tube defects (NTDs). The multiple markers include:

  • Alpha-fetoprotein (AFP) screening. Sometimes called maternal serum AFP, this blood test measures how much AFP is in your blood during pregnancy. AFP is a protein that the fetal liver normally produces, and it is present in the amniotic fluid. It crosses the placenta and enters your blood. Abnormal levels of AFP may suggest chromosomal abnormalities, neural tube defects, or defects in the baby’s abdominal wall.
  • Estriol. The placenta produces this hormone, which can be measured in the gestational parent’s blood or urine. Its level can be used to determine fetal health.
  • Inhibin. Also made by the placenta, this hormone is often higher when the fetus has Down syndrome.
  • Human chorionic gonadotropin. This is another hormone produced by the placenta. When measured in combination with the above substances in the second trimester, it can help providers determine the risk of chromosomal abnormalities[2]“Dimeric Inhibin A as a Marker for Down’s Syndrome in Early Pregnancy,” David A. Aitken, Ph.D. et al, The New England Journal of Medicine, May 9, … Continue reading.

These second trimester measurements can be combined with first trimester genetic screening results in various ways and might give more accurate results[3]“Prenatal Genetic Screening Tests,” American College of Obstetricians and Gynecologists (ACOG), You could hear this method called an integrated screening test, although this practice is less common with the development of non-invasive prenatal screening (NIPT). While the results of genetic screenings are delivered as positive or negative, it’s important to note that these measures are not diagnostic tests. To know for sure whether your baby has a chromosomal abnormality or neural tube defect, further investigation is required[4]“Second Trimester Prenatal Screening Tests,” Standford Children’s Health,


If second trimester genetic screening results come back positive and parents want to move ahead with diagnostic testing, the next step is amniocentesis. During this procedure, the provider inserts a long, thin needle through the abdomen into the amniotic sac to take a small sample of amniotic fluid. This fluid contains cells that the baby has shed, and they carry specific genetic information[5]“The Importance of Checkups in the Second Trimester,” Healthline Parenthood,

The physician may or may not use a local anesthetic to numb the skin. The use of ultrasound will help the medical team guide the needle to minimize the chance of harming the baby. There might be cramping after the procedure, and strenuous activity should be avoided for about 24 hours. The fluid is sent to a genetics lab for analysis, and results are typically available in 10-14 days.

20-Week Ultrasound

This detailed anatomy scan is usually recommended between 18-22 weeks and examines the baby’s bones and organs to make sure everything is developing normally. Some expectant parents decline first and second trimester genetic screening. If that’s the case, this mid-pregnancy ultrasound can often detect major abnormalities and anomalies.

Other benefits of having the anatomy scan include:

  • Determining the position of the placenta
  • Checking the amount of amniotic fluid
  • Examining blood flow patterns
  • Observing fetal behavior and activity
  • Measuring the length of the cervix
  • Monitoring fetal growth[6]“Common Tests During Pregnancy,” John Hopkins Medicine,

Glucose Screening

This test measures the amount of glucose in your blood. High blood sugar might be a sign of gestational diabetes (GD), which is a temporary form of diabetes that occurs in some pregnant people. GD can cause health problems for the baby, particularly if it goes undiagnosed or untreated.

The standard way to conduct this screening starts with drinking a special sugary drink. You will wait an hour, and a staff member in the lab will draw a blood sample that will be analyzed. Remember, this is a screening, so if the result shows your blood sugar level is high, you will have another type of glucose test to confirm the results. Glucose screening typically occurs between 24 and 28 weeks of pregnancy, but it could be done earlier if you have risk factors or had gestational diabetes in a past pregnancy[7]“Routine Tests During Pregnancy,” American College of Obstetricians and Gynecologists (ACOG), June 2020,

Takeaways About Second Trimester Testing and Screening

It’s normal to be nervous about screening and testing in the second trimester, but there are benefits to knowing as much as you can about your baby’s development. Discuss any concerns with your doctor or midwife and ask questions so you can make the best decision for your family.

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