If you or your spouse is currently pregnant and if you’re as curious as I am, you may wonder about all the checks and tests you and your unborn baby will go through. During your pregnancy you may hear a lot of new terms and not everything may make sense. That’s especially true if there are complications or if doctors decide to keep a close eye on your baby because of an abnormal test result. My wife and I were exactly in that situation when our baby boy was diagnosed with low PAPP-A levels. So in this post I’ll attempt to share all the good information we learned piece by piece and over the course of several weeks, in a consolidated form. This is meant to equip you with some basic knowledge, so that you can ask your doctor the right questions. Since I’m not a doctor, I strongly urge you to discuss anything that may or may not apply to you with your doctor – don’t draw your own conclusions based on what you read here or anywhere else.
First Trimester Screening
The First Trimester Screen is an optional non-invasive evaluation that combines a maternal blood screening test with an ultrasound evaluation of the fetus to identify risk for specific chromosomal abnormalities, including Down Syndrome Trisomy-21 and Trisomy-18. You will also be checked for two pregnancy related hormones: hCG and PAPP-A. None of those tests can determine definitively if there is a problem, they merely suggest a risk factor that could lead to closer monitoring and further evaluations. A newer test (also optional and you have to pay for it) called Harmony can determine certain chromosomal abnormalities with relative certainty.
Ultrasound & Fetal Monitoring
Fetal heart with closed valves
The most information we learned during countless ultrasound checks after our baby boy was diagnosed with Intrauterine Growth Restrictions (IUGR), which basically means the baby wasn’t growing according to the national average. IUGR is often caused by maternal factors, such as diabetes, high blood pressure, smoking etc but it can also be caused by issues with the placenta.
My wife didn’t have any of the above mentioned factors, so the theory was that her placenta wasn’t working properly. Why exactly the placenta wasn’t working properly we may never find out but I’m hoping for some answers when the pathology report comes back in a couple of weeks.
IUGR can be split into two categories: symmetric and asymmetric growth restriction.
Symmetric Growth Restrictions (SGR)
As the name implies, SGR means that the baby’s head circumference (HC) as well as abdominal circumference (AC) and femur are equally small in relation to their respective growth charts.
ASG at week 27
Asymmetric Growth Restrictions (AGR)
AGR means that the baby’s HC is larger than the AC. This happens when the baby redirects more blood to the brain, to preserve its growth, than to other organs. This is also called brain-sparing. AGR sounds worse than SGR – who wants a baby with a big head and a small body. In reality it’s actually good that the brain gets more blood so it can develop properly. Other organs are not as important and can catch up later if need be.
Our baby was diagnosed with AGR, most likely caused by a prematurely aging placenta, not delivering enough blood flow to the baby. Every placenta ages but it normally doesn’t degrade much until closer to the baby’s due date. In our case, aging had set in earlier causing insufficient blood flow through the placenta.
Amniotic Fluid
Often related to baby’s affected by IUGR are low amniotic fluid levels (AFL). Amniotic fluid (AF) consists mostly of baby’s urine. So low levels could indicate a kidney problem. Since our baby was pumping most of the blood to his brain, other organs were getting fewer nutrients, including the kidneys. That, in combination with maternal exhaustion and dehydration led to low AFL. Since one of the jobs of the AF is to make sure baby and the umbilical cord has enough room in the womb, low levels increase the risk of umbilical cord compression, which leads to a drop in fetal heart rate caused by less blood flow through the cord. If the cord is compressed for too long it could lead to fetal distress due to lack of oxygen.
Amniotic Fluid
Sonographers and perinatal doctors measure the so-called Amniotic Fluid Index (AFI) in quadrants. So they visually divide the amniotic sac in 4 quadrants and measure how much vertical unobstructed space (filled with fluid) is available. Adding up all 4 quadrants gives you the AFI in centimeters. When we got first admitted to the hospital my wife’s AFI was 5cm, well below the normal range of 8-18cm.
Umbilical Artery Doppler Assessment
Once IUGR is diagnosed, doctors will keep a close eye on your baby’s blood flow patterns to all major organs (kidney, liver, heart, brain…). They will also look at the blood flow through the umbilical cord. This is usually done by looking at so-called doppler waveforms. Blood flow in each blood vessel, such as arteries and veins, follows a distinctive pattern. If that pattern is off it can indicate a problem. You may be familiar with the terms systole and diastole from your last blood pressure (BP) measurement. In terms of umbilical blood flow, the systole measures the blood flow velocity while the heart is contracting and the diastole measures the blood flow velocity while the heart is relaxed. Doctors look at the ratio of systole and diastole to determine the so-called Resistance Index (RI). So you may hear doctors talk a lot about monitoring the resistance.
Umbilical Doppler Waveform
Low resistance means the peak and valley of the waveform are not too far apart. In the picture above the Systole (S) to Diastole (D) ratio is 2.59, which is considered normal. The closer the diastole (valley) to the base line, the more resistance there is. In the worst case, if the valley is below base line, doctors speak of reverse blood flow. In our case, the RI was increasing intermittently and it hit baseline at least once.
Fetal Circulation
Fetal blood circulation is actually more complex than it is until after the baby is born. The reasons for that are several shunts or ducts that are open while the baby is in utero but that close once the baby takes his first breath. Additionally the baby’s lungs are not working in utero because the placenta assumes the responsibility of oxygenating the blood. One of those ducts is called the Ductus Venosus and it’s located between the umbilical vein and the baby’s liver. Under certain circumstances this duct could prematurely close while the baby is in utero causing sudden death due to cardiac arrest.
In our case, this duct was structurally abnormal and dilated due to unknown reason, ultimately triggering the decision to immediately deliver the baby at week 30 and 6 days.
Fetal circulation
We also learned that the fetal heart has a hole to allow blood flow from the right to the left atrium. That hole also closed when the baby is born. This hole is the reason why you cannot take anti-inflammatory medications such as aspirin or ibuprofen during pregnancy, because they may trigger that hole to close prematurely. On the other hand neonatal doctors sometimes use similar medication to trigger closure of this hole if it doesn’t close by itself after delivery.
Fetal Monitoring
If complications with your pregnancy are detected, you will often end up in bed rest and connected to a fetal monitor. The fetal monitor keeps track of baby’s heart rate (HR). What doctors are looking for is variability. So instead of a straight line, indicating a consistent heart rate, doctors will look for frequent but minor changes in heart rate, indicating that the baby is active. They also want to see so-called accelerations. Periods of accelerations should last for 15 beats and the heart rate should increase by 15 beats above baseline.
Prolonged deceleration
So if your baby’s HR baseline if around 140 beats per minute (bpm), you want to see accelerations of 155 bpm or more, lasting for more than 15 beats. What you don’t want to see are so-called decelerations, especially if they occur frequently. Infrequent decelerations are normal and can occur when the baby accidentally compresses the umbilical cord while turning. A health baby notices a resulting drop in HR and tries to move away from the cord. A sick or growth restricted baby may not be able to tolerate such decelerations and that’s why they are a concern and are watched closely.
Other Non-Stress Tests
Other areas doctors keep a close eye on, especially during ultrasound exams include:
Fetal movement
Doctors look at how much the is baby moving during a 30 minute timeframe. They are looking for muscle tone (opening and closing of fists for example) and gross body movements of the torso and larger extremities.
Respiratory attempts
At a certain gestational age (we first noticed it around 28 weeks) baby is supposed to make respiratory attempts. In order words he should practice breathing by moving the so-called diaphragm up and down. The fetal diaphragm is seen as a hypoechoic curved line between the liver and the right lung.
Fetal diaphragm
Conclusion
I hope you find the information above useful. It took us several weeks to put all the pieces together, so if you are in a similar situation, this information may help you to get up to speed quicker.
I want to say thank you to all the caregivers who were treating both my wife and our healthy (albeit preterm) baby boy. In no particular order I want to say special thanks to the doctors and midwifes of Peachtree Women’s Clinic, the doctors and sonographers at Atlanta Perinatal Consultants and all the nurses and technicians at Northside Hospital. Keep up the great work!
References
http://www.fetal.com/IUGR/_umbilical2.html
http://www.fetal.com/IUGR/treatment.html
http://americanpregnancy.org/prenatal-testing/first-trimester-screen/
http://www.heart.org/HEARTORG/Conditions/CongenitalHeartDefects/SymptomsDiagnosisofCongenitalHeartDefects/Fetal-Circulation_UCM_315674_Article.jsp
http://americanpregnancy.org/pregnancy-complications/fetal-growth-restriction/
http://americanpregnancy.org/pregnancy-complications/oligohydramnios/
http://www.webmd.com/baby/electronic-fetal-heart-monitoring
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