The next topic that I really wanted to dig into for our birth plan was Fetal Monitoring. It’s come up a few times this pregnancy at some of my appointments, and the policy at my hospital is that all VBAC patients have continuous Electronic Fetal Monitoring during their time at Labor and Delivery. As I started to look into the research about fetal monitoring, it became clear that this is a HUGE topic! So, if you have the time to get through this I think you’ll learn a lot and be able to make a great informed choice for your own birth plan too.
My main concerns regarding continuous fetal monitoring during labor includes the accuracy of the monitoring and the affect it may have on my ability to stay mobile during labor. In this post, I’m going to go through a few different topics including the types of monitoring used, the various heart rate patterns that they are watching for during monitoring, and how that relates to VBAC specifically.
Types of Monitoring
There are two types of fetal monitoring used: Electronic Fetal Monitoring (EFM) and also Manual Auscultation. EFM is much more common, and enables providers to measure the response of the baby to contractions. It does this using two receivers, one for the fetal heart rate and one for measuring the strength on contractions. EFM has become much more popular since the 1980s, with original hope being that they could decrease the incidence of Cerebral Palsy. Although EFM is used in over 85% of hospital births, the rate of CP has not changed since WWII.
Manual Auscultation is when providers use a handheld device to listed to the fetal heartbeat while feeling for contractions using their hands. This type of fetal monitoring is most commonly used during care provided by a midwife, and usually more common in home birth and birthing center situations. There is no continuous monitoring when this is the method used.
What are they looking for?
A normal fetal heartbeat varies between 110 and 160 beats per minute, and potential problems with the fetus can be signaled by a heart rate that doesn’t vary, is too high, or too low. According to ACOG, there are three levels of classification for the print-outs, or tracings, generated by the EFM. Category 1 FHR Tracings are normal and no specific action is required. Category 2 tracings are considered indeterminate and evaluation, surveillance and possibly other tests should be used to determine if there is a problem. Category 3 tracings are abnormal and this may require additional actions like providing oxygen, changing positions, discontinuing labor stimulation (Pitocin), or treating maternal hypotension. If the providers aren’t able to get the tracings to return to normal, ACOG recommends that the baby be delivered as soon as possible.
So, who determines what category the tracings are? Your providers. This opens the door to a large variety of interpretations. In fact, according to a press release from ACOG, “The ACOG guidelines highlight a case in which four obstetricians examined 50 FHR tracings; they agreed in only 22% of the cases. Two months later, these four physicians reevaluated the same 50 FHR tracings, and they changed their interpretations on nearly one out of every five tracings.”1 ACOG recommends that women who have high-risk conditions such as preeclampsia, type 1 diabetes, or suspected fetal growth restriction (IUGR) be monitored continuously during labor.
Fetal Heart Rate during VBAC
I really want to focus more on how this impacts mothers who are going through a VBAC birth. Understanding how providers use these tracings to monitor VBAC patients can give us some insight into why they have policies in place that require continuous EFM for those patients. When speaking to my provider, they said that fetal distress is often the first sign of Uterine Rupture, and that is why they have their policy.
“In a larger study, Leung et al. analyzed the FHR and uterine contraction pattern immediately prior to 78 cases of uterine rupture. Prolonged deceleration was defined as a FHR less than 90 beats per minute that exceeded 1 minute without return to baseline. Prolonged deceleration (alone or proceeded by either severe late or variable decelerations) occurred in 71% (n = 55/78) of the cases of uterine rupture. In addition, prolonged deceleration occurred in 100% (n = 36/36) of the FHR tracings in which total fetal extrusion occurred. If more than one type of periodic deceleration, in addition to a prolonged deceleration was present, only the most ominous pattern was recorded. Late decelerations were considered most ominous, followed by variable and early deceleration. Although late decelerations were more common preceding the prolonged deceleration that heralded uterine rupture, this finding may be an artifact of the study methodology.”2
I know that a lot of that is some very technical language, so now lets explore what some of those heart rate patterns mean.
Fetal Heart Rate Patterns
- Fetal Tachycardia, defined as a baseline heart rate greater than 160 bpm and is considered a nonreassuring pattern. Between 160 and 180 bpm it is considered mild and over 180 bpm is considered severe. Over 100 bpm is usually due to fetal tachyarrhythmia or congenital anomalies. Some causes of fetal tachycardia include maternal fever, hyperthyroidism, maternal or fetal anemia, Chorioamnionitis, and prematurity. Fetal tachycardia may be a sign of increased fetal stress when it persists for 10 minutes or longer, but it is usually not associated with severe fetal distress unless decreased variability or another abnormality is present.3
- Fetal Bradycardia is defined as a baseline heart rate less than 120 bpm with 100-120 bpm range not associated with fetal acidosis. It is common in post-date gestations and in fetuses with occiput posterior or transverse presentations. A FHR below 100 bpm is usually associated with babies with congenital heart abnormalities. Moderate bradycardia of 80 to 100 bpm is a nonreassuring pattern. Severe prolonged bradycardia of less than 80 bpm that lasts for three minutes or longer is an ominous finding indicating severe hypoxia and is often a terminal event. Causes of severe bradycardia include prolonged cord compression, cord prolapse, tetanic uterine contractions, paracervical block, epidural and spinal anesthesia, maternal seizures, rapid descent, and vigorous vaginal examination.
Both Tachycardia and Bradycardia are considered longer term patterns to watch for. There are some short term or periodic FHR changes that should also be noted.
- Accelerations are usually associated with fetal movement, vaginal exams, contractions, umbilical vein compression, fetal scalp stimulation or external acoustic stimulation. They are considered a sign of fetal well-being, and are the basis of the nonstress test (NST) that many providers recommend to women who are past their due date. The presence of at least two accelerations, each lasting for 15 or more seconds above baseline and peaking at 15 or more bpm, in a 20-minute period is considered a reactive NST, which is a good thing.
- Early Decelerations have a uniform shape, with a slow onset that coincides with the start of the contraction and a slow return to the baseline that coincides with the end of the contraction. Meaning that the heart rate will decrease at the start of the contraction, and then return to baseline after the contraction. Early decelerations are reassuring, and not an indication of fetal distress, but they need to be identified to avoid confusion with other nonreassuring decelerations.
- Late Decelerations are caused by uterine contractions and are associated with uteroplacental insufficiency, which means that there is a decrease in uterine blood flow or there is a placental dysfunction. Some causes include postdate gestation, preeclampsia, chorinic hypertension and diabetes mellitus. A late deceleration starts at or after the peak of a contraction and the heart rate doesn’t return to baseline until after the contraction ends. According to the Association of American Family Physicians (AAFP), all late decelerations are considered Category 3 situations and a pattern of them is nonreassuring.
- Variable Decelerations. These are shown on the FHR tracings in “U”, “V” or “W” pattern and may not have a constant relationship with the uterine contractions. They are common in patients who have experienced premature rupture of membranes (PROM) and decreased amniotic fluid volume. They are caused by compression of the umbilical cord. Variable Decelerations can be complicated, “Variable decelerations may be classified according to their depth and duration as mild, when the depth is above 80 bpm and the duration is less than 30 seconds; moderate, when the depth is between 70 and 80 bpm and the duration is between 30 and 60 seconds; and severe, when the depth is below 70 bpm and the duration is longer than 60 seconds. Variable decelerations are generally associated with a favorable outcome. However, a persistent variable deceleration pattern, if not corrected, may lead to acidosis and fetal distress and therefore is nonreassuring.”3
- Sinusoidal heart rate patterns are associated with high rates of fetal morbidity and mortality, and is considered a Category 3 FHR pattern. It indicates severe fetal anemia, which can happen in cases of Rh disease or severe hypoxia. On the FHR tracings it looks like a regular, smooth, undulating wave that happens two to five times per minute and has a range of 5-15 bpm. It is also characterized by a stable baseline heart rate between 120 to 160 bpm, and doesn’t have variability between the beats.
How to Decide
Now that I know more about the different types of heart rates that they can see using the EFM and what they can indicate, I understand more why my hospital would require this for VBAC patients. However, my main concerns with continuous fetal monitoring haven’t changed. How can I be sure that the providers are accurately reading the FHR tracings? I have to have trust in those that are there and that they have the experience and knowledge to interpret them. How can I preserve my ability to stay mobile during labor? I am going to request that they use a wireless model of the EFM so that I can be comfortable while being monitored.
During my 35 week appointment, I talked to my midwife about my concerns and we talked in detail about how they ensure that multiple people are looking over the tracings before initiating the decision to have a cesarean section and that they work hard to try other options before resorting to surgery. She also explained how they have installed wireless receptors for their monitors throughout the birth center so that whether I am in my room or walking the halls they will be able to find me if they need me and I will still be able to have the mobility that I really want.
Although it’s not ideal to me to have continuous monitoring, I think that it will be something that I can work with. If during my labor I change my mind, we will cross that bridge when we get there. Did you have continuous monitoring during your labor? Were you able to have a wireless version? What was your experience like? I’d love to hear from other mamas about their experience!
- American College of Obstetricians and Gynecologists, June 22, 2009. (31 December 2014) (http://www.acog.org/About-ACOG/News-Room/News-Releases/2009/ACOG-Refines-Fetal-Heart-Rate-Monitoring-Guidelines
- O’Brien-Abel, Nancy, RNC, MN. “Uterine Rupture During VBAC Trial of Labor: Risk Factors and Fetal Response” (31 December 2014) http://www.medscape.com/viewarticle/458963_5
- Sweha, Hacker and Nuovo. Association of American Family Physicians. “Interpretation of the Electronic Fetal Heart Rate During Labor” (31 December 2014) http://www.aafp.org/afp/1999/0501/p2487.html