What classifies a high-risk pregnancy?
It’s difficult to estimate exactly what percentage of pregnancies are high-risk, considering that a standardized definition of a “high-risk pregnancy” is not available. “It’s such a broad term and there are so many nuances,” said Dr. Amelie Pham, an obstetrician/gynecologist with the Vanderbilt High-Risk Pregnancy Care program.
Some risk factors are related to the mother’s health, including conditions like autoimmune disorders or kidney disease. Prior pregnancy history, such as a history of miscarriages, stillbirth or being under 20 or over 35 — an “advanced maternal age” — at the time of a first pregnancy can put a person’s pregnancy in the high-risk category as well.
Other high-risk pregnancies stem from abnormalities or birth defects detected in the growing fetus. These are typically discovered via early genetic screening test or during the anatomy scan, also known as the 20-week ultrasound.
Getting support from a perinatologist
The vast majority of reasons why your pregnancy might be considered high-risk are manageable. For some, having a high-risk pregnancy simply means an additional ultrasound or two. For others, it can mean having their care transferred over to a maternal-fetal medicine specialist to help monitor for pregnancy complications and create a modified birth plan. Maternal-fetal medicine specialists, also called perinatologists, are OBs with additional training in high-risk pregnancies. They can diagnose and treat conditions, abnormalities and defects affecting you and your baby during pregnancy.
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Prenatal tests to assess risk
Maternal-fetal medicine specialists often work with genetic counselors to help you understand whether your pregnancy is at increased risk for being affected by a genetic condition (Down syndrome, for example). These experts can discuss the different testing options and, if you decide that you want prenatal testing, can perform those tests and help you understand the results.
For example, non-invasive prenatal screening is an optional blood test that screens for more common genetic conditions such as trisomy 21 (Down syndrome), trisomy 13 (Patau syndrome) and trisomy 18 (Edwards syndrome).
“This test is also known as cell-free DNA screening,” said Brighton Goodhue, a certified genetic counselor and member of the high-risk pregnancy team at Vanderbilt Women’s Health. “It works by analyzing small fragments of genetic information from the placenta that can be detected in the maternal bloodstream during pregnancy.”
Expert care for you and your baby
What to expect at your 20-week ultrasound
Some pregnancies are deemed high-risk because of fetal abnormalities detected during the mid-trimester anatomy scan, also called the 20-week ultrasound. Between 19 and 22 weeks, a sonographer will measure your baby’s growth and see how they’re doing in utero.
“The 20-week scan is focused on evaluating the fetal anatomy and checking that your baby is growing appropriately,” said Sybil B. Tremblay, a registered diagnostic medical sonographer at Monroe Carell Jr. Children’s Hospital at Vanderbilt.
Your sonographer will be looking at:
- Key anatomy, including heart structures, the brain and internal organs
- Anatomical measurements such as head circumference, abdominal circumference and length of the long bones
- The position of your placenta and where it connects to the umbilical cord
- The amount of amniotic fluid in your uterus
- Fetal behavior and activity
- Blood flow patterns, which might be color-coded in red or blue to show the direction of the blood flow
- The baby’s sex
If the ultrasound is abnormal or shows a possible anomaly, Vanderbilt Women’s patients are referred to the Reed Family Maternal Fetal Clinic at Vanderbilt to reassess and confirm with another ultrasound. At this appointment, they will speak to a maternal-fetal medicine doctor about the ultrasound findings. Depending on the diagnosis, other specialized providers along with a genetic counselor and a social worker may be involved.
The Fetal Center at Vanderbilt
What is amniocentesis?
Based on family history or if non-invasive prenatal screening results are “high-risk,” you may be offered an amniocentesis. During an amniocentesis, a needle is inserted through the abdomen, uterus and amniotic sac to sample the baby’s amniotic fluid, which can then be sent off to the lab for various tests.
This test can help diagnose various genetic conditions and fetal abnormalities, including Down syndrome, cystic fibrosis, muscular dystrophy, sickle cell disease and more. With amniocentesis, there is a small risk of pregnancy loss, less than 1% when in the second trimester. If you have a blood-borne disease such as HIV or hepatitis C, there may also be a risk of disease transmission to the fetus.
Cesarean section vs. vaginal birth for high-risk pregnancies
“Although we generally recommend vaginal delivery for patients, there are several reasons that a cesarean delivery would be the preferred method of delivery,” said Dr. Soha S. Patel, a Vanderbilt Health maternal-fetal medicine physician specializing in high-risk pregnancy care. “A C-section can be life-saving under specific clinical circumstances.”
The most common reasons for a cesarean birth in the United States are:
- Inability to progress during labor
- If the baby is showing signs of distress before or during labor
- If the baby is “breech” or in another position that can prevent a safe vaginal birth
- If you have had previous cesarean deliveries, or any contraindications to vaginal birth
Other indications for a cesarean birth include an abnormal location of the placenta or umbilical cord, an infection that prevents a safe vaginal delivery, or fetal abnormalities where vaginal birth may be too risky. Cesarean operation recovery takes longer than recovery after vaginal birth, and you will likely stay in the hospital for two to three days so your health care team can monitor you for bleeding, infection, blood clots or injury to other organs near the uterus.
Prepare for a safe delivery
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