Overview of Antenatal Fetal Surveillance
Antenatal fetal surveillance, or checking on your baby before birth, aims to reduce the risk of stillbirth. For about 40 years, doctors have been using techniques to monitor babies’ heartbeats, using ultrasound and umbilical artery Doppler velocimetry (which measures blood flow in the umbilical cord) to monitor babies’ well-being. These methods become more important during pregnancies with conditions like diabetes, or where the baby isn’t growing properly. Heartbeat patterns, activity levels, and muscle movements can all be impacted by a lack of oxygen (hypoxemia) and a high level of acid in the body (acidemia).
In cases where a baby is experiencing a lack of oxygen, blood can be redirected to other areas of the body. This can reduce blood flow to the kidneys, causing a condition called oligohydramnios (low levels of amniotic fluid). Techniques such as cardiotocography (monitoring the baby’s heart rate during labor), ultrasounds, and tracking a mother’s perception of the baby’s movements can help detect potential issues with the placenta, the organ that provides oxygen and nutrients to your baby. If doctors can identify these problems in time, they can intervene before it leads to a serious problem like stillbirth. However, sudden severe changes in the baby’s health, like placental abruption (when the placenta peels away from the inner wall of the uterus) or umbilical cord accidents, can often not be predicted or prevented by these tests.
The American College of Obstetricians and Gynecologists (ACOG) suggests when to start antenatal fetal surveillance based on the risk of stillbirth. However, strict guidelines haven’t been made because there isn’t a lot of evidence-based research. As such, the ACOG encourages each case to be handled individually, especially in high-risk pregnancies. For instance, surveillance may start earlier in pregnancies where early delivery could improve the outcome for the baby. Doctors may suggest surveillance for pregnancies that have a higher chance of stillbirth.
Several methods are used for surveillance, such as monitoring a baby’s movements, contraction stress tests (measuring the baby’s heart rate during contractions), nonstress tests (checking the baby’s heart rate during movement), biophysical profiles (a prenatal ultrasound evaluation of fetal well-being), and umbilical artery Doppler velocimetry. Normal results from these tests generally indicate the baby is doing well. However, these methods may not correctly show how severely a baby is affected during acute distress and are less effective at predicting stillbirths due to sudden changes in maternal-fetal status.
If there are fewer baby movements noticed by the mother, further tests may be needed. Unusual findings might lead to additional testing or considering delivery. The decision on what to do with mixed or abnormal test results depends on the stage of the pregnancy. For very low scores, delivery is often the best choice, except when the pregnancy is less than 32 weeks, where more monitoring might be needed. Abnormal test results need careful examination to avoid unnecessary interventions. If labor is attempted, continuous monitoring during birth is advisable. While counting fetal kicks is a common method to assess a baby’s well-being, its effectiveness in preventing stillbirth isn’t proven and might lead to increased medical interventions.
Why do People Need Antenatal Fetal Surveillance
Antenatal fetal surveillance is a way to monitor the health of a baby in the womb, specifically to prevent tragedies like stillbirth, particularly in risky pregnancies. Babies in the womb can suffer from conditions such as lack of oxygen or a buildup of acid in their blood, both of which can be fatal. To catch any potential issues before they become serious, doctors use various methods of monitoring, including checking the baby’s movements, heart rate, and changes in the fluid around the baby in the womb.
Although there aren’t any established guidelines for all scenarios, most doctors and experts agree that these monitoring methods can be very helpful. The decision to monitor and how often to do so depends on a variety of things, like the risk of stillbirth for the mother, any existing health issues, complications in the pregnancy and the baby’s condition. Because the risk of stillbirth can increase as the pregnancy progresses, doctors have to carefully weigh the potential benefits and risks.
Sometimes, monitoring might return what’s known as a false positive, meaning the test shows a problem when there isn’t one. While this can be stressful and costly, the intention is to identify potential problems earlier rather than later. The timing and frequency of these checks depend on each individual pregnancy.
Here are some potential reasons for antenatal fetal surveillance:
Things related to the mother might include:
- High blood pressure (chronic and resulting from pregnancy)
- Being diagnosed with diabetes, lupus, antiphospholipid syndrome, sickle cell disease, kidney disease, or thyroid disease
- Alcohol or drug abuse
- Pregnancy using in vitro fertilization (IVF)
- Being aged 35 or older
- Being obese
Things related to the baby can include:
- Growth restriction
- Being pregnant with multiples (like twins or triplets),
- Noticing less fetal movement
Things related to the pregnancy itself can include:
- A history of complicated pregnancies or stillbirths
- Complications like cholestasis, vasa previa, or placental abruption
- Being pregnant past your due date
- Having too much or too little amniotic fluid
When a Person Should Avoid Antenatal Fetal Surveillance
Antenatal fetal surveillance, or the monitoring of a baby’s health during pregnancy, should be carefully considered based on individual circumstances. This is especially true for high-risk pregnancies or for women with multiple existing health issues. Starting such monitoring before 32 weeks of pregnancy can be tricky because babies born earlier often show false signs of distress during the tests, which can lead to unnecessary worry or even the decision to deliver the baby early.
An NST, or Non-Stress Test, is a standard monitoring method that can also have limitations, especially before 32 weeks of pregnancy. Similar to the case mentioned earlier, these tests too can often show signs of distress in the baby, not because the baby is actually in distress, but because it hasn’t fully matured yet.
The doctors need to weigh the pros and cons of these types of monitoring, considering the potential for getting false alarms and leading to unnecessary procedures. In the later stages of pregnancy, it’s important to strike a balance between the risks of constant monitoring against the possible benefits, like lessening the risk of stillbirth.
It’s also important to note that fetal surveillance is not helpful in predicting outcomes or telling how well a baby is doing for patients with sudden, serious situations like evolving placental abruption (when the placenta starts to separate early from the uterus) or cord prolapse (when the umbilical cord drops into the vagina ahead of the baby). These conditions require immediate medical exams and may quickly lead to the decision to deliver the baby.
Equipment used for Antenatal Fetal Surveillance
There are various tools that doctors use to check on the health of unborn babies and their mothers. These tools can track heart rate, contractions, the amount of fluid around the baby, and the blood flow in the umbilical cord. They are used in different ways to monitor how the baby is doing during the pregnancy. Here’s a simple explanation for each of them:
1. External fetal monitor: Also known as a cardiotocograph, this device measures the heartbeat of the baby and the mother’s contractions.
2. Intravenous oxytocin: Oxytocin is a medicine that may be given in the vein during a contraction stress test (CST). This is done to see how the baby’s heart reacts to the stress of contractions.
3. Vibroacoustic stimulator: This device might be used during a non-stress test (NST) which monitors the baby’s heart rate. It produces sound and vibration to encourage the baby to move, which leads to changes in the baby’s heart rate.
4. Ultrasound with Doppler velocimetry: This tool uses sound waves to create pictures of the baby and measures blood flow in the umbilical cord. It’s used during a Biophysical Profile (BPP), which is an ultrasound assessment of the baby’s wellbeing, and for checking blood flow specifically in the umbilical artery.
Preparing for Antenatal Fetal Surveillance
When doing Non-Stress Tests (NSTs), which are simple, non-invasive tests done during pregnancy, doctors usually ask patients to lie on their left side or partly sit up in what’s called the semi-Fowler position. This is done to reduce the pressure on major blood vessels that could interfere with the blood flow to your baby. Different studies have mixed results about which position is the best for these tests. Some studies show that lying on the left side can provide better results, while others suggest the semi-Fowler position is more effective.
However, a recent study has shown that both positions, the left side and semi-Fowler, are equally effective. Still, the comfort of the patient matters too. Some patients may notice that their baby is more active in certain positions. In performing a Contraction Stress Test (CST), which checks if your baby will stay healthy during contractions when you’re in labor, the American College of Obstetricians and Gynecologists (ACOG) suggest patients should lie on their side. Ultimately, the primary purpose is to get accurate test results while ensuring mom’s and baby’s comfort and safety.
How is Antenatal Fetal Surveillance performed
Monitoring your baby’s health while you are pregnant includes several different tests. These can include tracking the baby’s movements, heart rate tests, stress tests, and ultrasound exams. The timing and frequency of these tests depend on each individual’s circumstances, and there’s no one-size-fits-all schedule.
As a general guideline, most patients start fetal wellness testing around the 32nd week of pregnancy. The type of test and how often it is done depends on why the test is necessary. For example, if the issue might resolve itself, such as decreased fetal movement, repeated testing isn’t needed. But for chronic high-risk conditions, weekly tests are often suggested, increasing to twice a week or more if there is a potential for rapid changes in the baby’s health or abnormal test results.
Also, things like diabetes or fever in the mother can affect the test results. Doctors usually treat these problems and repeat the test later.
Monitoring Baby’s Movements
Counting the baby’s kicks is an easy way to monitor the baby’s well-being. Normal baby movement usually means the baby’s heart, nervous system, and muscles are developing well. However, a study of over 450,000 babies didn’t find a big difference in baby health outcomes between mothers who did kick counts and those who didn’t. But mothers who did kick counts did have more early deliveries and cesarean sections.
Different methods can be used to count kicks, and there is no established best way. A common method is for the mother to lie on her side and count the number of movements until she feels 10 distinct movements within two hours. Another method suggests counting movements for one hour, three times a week.
Heart Rate Test
Testing the baby’s heart rate (called cardiotocography) usually lasts at least 20 minutes. Doctors watch for consistent patterns in heart rate and rhythm. A healthy test result (called reactive) shows at least two instances where the baby’s heart rate increased quickly and returned to normal within a 20-minute period. If this doesn’t occur, further testing may be necessary. If the test still doesn’t give clear results, a different type of testing may be suggested.
Contraction Stress Test
If the heart rate test shows possible problems, a contraction stress test may be done next. This test watches how the baby’s heart rate responds to contractions. If the baby’s heart rate slows during a contraction, it may indicate that the baby isn’t getting enough oxygen.
Ultrasound Exam
Since the 1970s, ultrasound exams (known as biophysical profiles) have been used to monitor the baby’s heart and blood flow, as well as movements and overall development. Research has found a clear relationship between the score from an ultrasound exam and the baby’s overall health.
Possible Complications of Antenatal Fetal Surveillance
Monitoring the baby’s health before birth, also known as antenatal fetal surveillance, can sometimes lead to problems. One issue is the chance of ‘false-positive’ results, meaning the tests show a problem when there isn’t one. This can cause needless further tests or actions, like a premature birth. An opposite problem is ‘false-negative’ results, where the tests miss a real issue, not flagging the need for additional check-ups.
There is also a concern among some experts that these tests might lead to babies being born with severe conditions, such as cerebral palsy. This could happen if alarming test results lead to early delivery, allowing a baby with severe neurological issues to survive, instead of leading to a natural end of pregnancy.
We also don’t fully understand how this type of testing affects the mental health of pregnant women. Undergoing these tests could cause anxiety, but if the results are good, it might also bring peace of mind. Other considerations include the costs of testing. This not only refers to financial costs but also the time spent by patients and healthcare workers, as well as potential health risks to the mother and baby due to unnecessary interventions prompted by false-positive results.
In general, obstetricians consider using ultrasound scans during pregnancy to be safe. However, the American College of Obstetricians and Gynecologists (ACOG) advises being conservative with interventions during pregnancy. While ultrasounds are known to be safe, the possible effects of exposure to ultrasound waves for a long time, or repeatedly, on a fetus are still not fully understood. Therefore, ACOG encourages the ‘As Low As Reasonably Achievable’ principle, which means only using interventions like ultrasound when there’s a clear reason to do so.
Healthcare providers also need to be aware of the heat produced by the ultrasound device. This heat is shown on the ultrasound screen as a ‘thermal index’. The best practice is to use settings that keep this index as low as possible.
What Else Should I Know About Antenatal Fetal Surveillance?
If you’re pregnant and have certain conditions like diabetes, or complications like issues with your baby’s growth, your doctor will keep a close eye on your baby’s health before they’re born. They use different techniques to check if the baby might be at risk of not surviving. If they notice anything outside of the normal range, they’ll have a closer look. It’s really important to remember that a lot of factors like the baby’s age, what medications you’re taking, and your overall health, can influence these results. Some medications — such as those used for pain relief or to reduce seizures, or even blood pressure drugs — can decrease your baby’s heart rate. Smoking can also affect the baby’s heart rate.
Sometimes a mom might start to notice a decrease in her baby’s movements. Research has found that when moms sense their babies moving less overall, it’s a better indicator of potential problems than counting a certain number of kicks. So if you feel like your little one isn’t moving as much, or the counts of your baby’s kicks are lower than usual, your doctors can perform further assessments.
One test they can use is called a Nonstress Test (NST). They check your baby’s heart rate when he or she moves. If the heart rate increases by at least 15 beats per minute above the regular rate for a minimum of 15 seconds, it’s a good sign your baby is fine. If there aren’t enough heart rate increases, they’ll examine your baby further.
Sometimes there can be unusual, quick decreases in the baby’s heart rate, which don’t usually require intervention unless they keep occurring, or the baby’s heart rate slows down for a long period of time. In such cases, they may perform another test called the Biophysical Profile.
The NST is often not as effective in preterm babies; that is, babies which are not fully developed yet. NST’s effectiveness tends to increase as the baby grows and reaches between 24 and 32 weeks.
In another test, called the Contraction Stress Test (CST), they look at the baby’s heart rate when the mother is having contractions. Depending on the results, they classify the CST as negative, positive, suspicious, equivocal (uncertain), or unsatisfactory and decide what to do next based on that.
The Biophysical Profile (BPP) involves a scoring system where a high score suggests the baby is doing well. If the score is low, or the amount of amniotic fluid around the baby is less than what it should be, they may evaluate your baby further or discuss what the next steps should be. Scores of 6 and lower usually mean deciding whether to deliver the baby or not, given the baby’s and mom’s health conditions.
A variant of the BPP, called the Modified Biophysical Profile, also involves checking the baby’s heart rate and the amount of amniotic fluid. If either of these aspects is abnormal, then a full BPP or CST is recommended.
Umbilical Artery Doppler Velocimetry is another test that checks the flow of blood in the umbilical artery. If there are abnormalities in this test, it could mean a higher risk for the baby and indicate issues with the placenta or that the baby isn’t getting enough oxygen. They will evaluate multiple blood flow patterns to ensure they have an accurate assessment.
