During labor, a healthy baby responds to contractions by temporarily changing heart rate. This is normal and healthy - it means your baby's body is working properly and responding to contractions just as your body would respond to exercise. The invention of the fetoscope (a specialized stethoscope) changed birth. It allowed the midwife to listen to the baby's heart beat before it was born, alerting her to potential problems. As technology advanced, so did listening to the baby's heart. Today specialized ultrasound machines called electronic fetal monitors are able to print a continuous record of your baby's heart rate and your contraction pattern
There are differnt ways to monitor the baby in labor. Your ability to choose any of these options will depend on their availablity at your birth place and the circumstances of your labor. For example, some health conditions or medications used during labor will require continuous monitoring. Some health systems and communities rely more heavily on one type of monitoring rather than antoher. Be sure to ask what is used in your community.
Stethoscope or Fetoscope
A stethoscope is the device your midwife uses to listen to your heart. A fetoscope looks similar to a stethoscope, but has a larger bell to allow the user to hear the babies heart beat. Both work by amplifying the sound of the heart beat, and can be used any time during labor. The sound is soft and subtle, and proper placement is necessary. Additionally, the bell will be held firmly on your abdomen (firm enough to leave a ring for a short time when removed) to ensure the best sound.
Stethoscopes and fetoscopes are relatively cheap, so nearly every practitioner has one. But not all practitioners have developed the skill to listen to fetal heart tones with a stethoscope or fetoscope. This method requires your midwives or her assistant's hands on the monther's belly to hold the bell in place. Depending on the length of the tubing, the mother may need to lie on her back. A stethoscope or fetoscope is not an option when continuous monitoring is required.
A Pinard Horn is an elongated bell with a wide end for placing on the mother and a narrow end for placing against the listener's ear. It gently amplifies the sound of the fetal heart beat and can be used at any time during labor. Similar to the stethoscope and fetoscope, the sound is subtle so proper placement is necessary. This device will also require hands on your abdomen to hold the device firmly (firm enough to leave a ring for a short time when removed).
Pinard Horns are relatively cheap, and versitile. They come in a varitey of lengths. including a stlye long enough for use in wterbirth, and can be made of wood, plastic or metal. For best listening with most horns, the mother must lie on her back. A Pinard horn is not an option when continusous monitoring is required.
DoptoneThe doptone is a hand held ultrasound tool. It works by sending a high frequency sound wave into your body, and then retrieving the sound wave as it bounces back. Specially made doptones are useful underwater, where other electronic monitoring tools might be damaged. The long cord connecting the lead to the hand-held unit gives more flexabilty to pick up heart tones with the mother in different positions, which means the midwife can be unobtrusively monitor while the mother continues with what feels best to her. Because it is hand-held, a doptone can not be used when continuous monitoring is required.
Electronic Fetal Monitor
The electronic fetal monitor (EFM) is an ultrasound device that records the baby's heart beat and the relative strength of a contraction on a strip of paper. This allows the midwife to see how the baby has been responding to contractions over a long period of time without having to hold a listening device onto mothers abdomen, or even be in the room. This has led to some criticism of the device by experts who feel that if a woman needs to be monitored, she should be monitored by a person who can respond immediately in the event of an emergency rather than 15 to 30 minutes later when the strip of paper is reviewed.
There was an expectation that the ability to more closely track a baby's heart rate would improve outcomes for babies. If a midwife were able to see a problem earlier, she should be able to intervene before damage is done. Unfortunately, electronic fetal monitoring has not lived up to its expectations. Its use is associated with an increased cesarean surgery rate without a increase in the health of mother or baby. This may be due to the relatively high rate of false readings, meaning the EFM printout is read as fetal distress when none exists.
Being attached to wires connected to a small box has the potential to be uncomfortable in several ways. Some mothers find the belts used to attach the monitor itchy or uncomfortable. The wires limit mobility, reducing the available space to about four feet around the box. The monitors can be fussy, requiring mothers to shift positions to help the monitor get a better reading rather than for comfort.
Telemetry is an electronic fetal monitor without wires. It does not improve the false readings of an EFM, but it does eliminate many of the problems associated with mobility and positioning. Some telemetry units are safe to use in water. Telemetry is not available in all hospitals.
Internal Fetal Monitor
The internal fetal monitor uses an tiny electrode that punctures the baby's skin to get the most accurate reading of the baby's condition available. In some cases a pressure monitor will also be used to measure the relative strength of contractions. The electrodes are inserted through the vagina into the uterus. The wires are taped to the mother's leg so they do not get pulled out when she shifts position.
Internal monitoring requires the bag of water be broken, which increases the pressure on the baby's head. This increases the risk of dilating with a cervical lip (part of the cervix doesn't stretch back). It also requires the mother lay relatively still to prevent pulling on the wires.
Types of Monitoring
Not all monitoring is the same. Depending on the situation, options for types of monitoring may be limited.
Some hosptials do not have access to some types of monitoring. In the United States, almost every woman has electronic fetal monitoring at some point in labor. 90% of the respondents on the Listening to Mothers II Survey had continuous monitoring which means they were attached to the electronic fetal monitor throughout the entire labor.
Medications used during labor increase the likelihood that your baby will not tolerate contractions well. When you use medications to cause contractions or to relieve pain during contractions, your baby will be monitored continuously to ensure any changes in heart rate are recognized.
Unless you are planning an unassisted home birth, having no monitoring is basically an impossibility. You are paying your midwife to alert you if anything becomes unhealthy, and monitoring is one of the ways a midwife will do that.
With intermittent monitoring you will spend a designated amount of time being monitored, maybe so many minutes per hour or two, and the rest of the time will be free to move around. The monitoring may be done with a sthethoscope, fetoscope, Pinard Horn, doptone or by attaching an electronic fetal monitor to you.
In some situations, such as when you choose to use a medication or some types of inductions, it is necessary to monitor your baby continuously. This can be done with an electronic fetal monitor, telemetry unit or internal monitor.
The risk of not monitoring would be that your baby may have a problem that goes undetected. The two most common problems in labor without medications are hemorrhage (mother does not stop bleeding fast enough after the placenta is out) and a baby who does not breathe right away after being born. Neither of these problems (which according to Henci Goer account for 75% of the 5% of problems in labor) are detectable or preventable with monitoring.
It has generally been assumed that the more you monitor, the better off the baby and mother will be. However, Henci Goer reports in The Thinking Woman's Guide to a Better Birth that studies have failed to find a link between increased monitoring and better outcomes. In fact, the studies have shown that continuous use of the electronic fetal monitor increases the chances of a cesarean surgery without the expected improvements in health.
There are some experts who are concerned about the use of ultrasound in monitoring. They feel that it has not been fully tested to ensure safety.
Non-medical risks to monitoring may include:
False readings may cause panic or fear
Discomfort due to restricted positioning
Discomfort due to breaking of bag of waters
Discomfort of EFM band attached to abdomen
Thacker SB, Stroup D, Chang M. Continuous electronic heart rate monitoring for fetal assessment during labor (Cochrane Review). In: The Cochrane Library, Issue 1, 2004. Chichester, UK: John Wiley & Sons, Ltd.
This review found that the only benefit to coninuous ehrm is in the reduction of neonatal seizures. Because continuous EFM increases C-sect and operative delivery rates it is recommended that the woman and doctor discuss the benefits and risks of continuous EFM before deciding to use.
Bricker L, Neilson JP. Routine Doppler ultrasound in pregnancy (Cochrane Review). In: The Cochrane Library, Issue 1, 2004. Chichester, UK: John Wiley & Sons, Ltd.
Reviewers' conclusions: Based on existing evidence, routine Doppler ultrasound in low risk or unselected populations does not confer benefit on mother or baby. Future research should be powerful enough to address small changes in perinatal outcome, and should include evaluation of maternal psychological effects, long term outcomes such as neurodevelopment, and issues of safety.
Bricker L, Neilson JP. Routine ultrasound in late pregnancy (after 24 weeks gestation) (Cochrane Review). In: The Cochrane Library, Issue 1, 2004. Chichester, UK: John Wiley & Sons, Ltd.
Reviewers' conclusions: Based on existing evidence, routine late pregnancy ultrasound in low risk or unselected populations does not confer benefit on mother or baby. There is a lack of data about the potential psychological effects of routine ultrasound in late pregnancy, and the effects on both short and long term neonatal and childhood outcome. Placental grading in the third trimester may be valuable, but whether reported results are reproducible remains to be seen, and future research of late pregnancy ultrasound should include evaluation of placental textural assessment.
ACOG Technical Bulletin Number 132 - September 1989
"Previously, it had been presumed that continuous electronic fetal monitoring would be more sensitive and accurate than intermittent ausculation in detecing heart rate patterns that indicated significant fetal compromise. This presumption has not been supported by recent randomized prospective studies, however. Currently available data support the conclusion that, within specified intervals, intermittent auscultation is equivalent to continuous electronic fetal monitoring in detecting fetal compromise."
Luthy DA, Shy KK, van Belle G, et al. A randomized trial of electronic fetal monitoring in preterm labor. Obstet Gynecol 1987; 69:687-95.
Abstract: Intrapartum electronic fetal heart rate (FHR) monitroing and fetal blood gas sampling were compared with periodoic auscultation of FHR in a multicentered randomized trial of preterm singleton pregnancies with fetal weights of 700-1750 g. Two hundred fory-six pregnancies were studied (electronic FHR monitoring N=122, auscultation N=124). Perinatal or infant death was associated with 14% of pregnancies with electronic FHR monitoring and 15% with auscultation. No significant differences were noted in the prevalence of low five-minute Apgar scores, intrapartum acidosis, intracranial hemorrhage, or frequency of cesarean section (P > .10). Cormpared with electronic FHR monitoring, intrapartum auscultation as done in this study is unlikely to be associated with detectable difference in perinatal outcomes within the high-risk setting of preterm labor.
Shy KK, Luthy DA, Bennett FC, et al. Effects of electronic fetal heart rate monitoring as compared with periodic auscultation on the neurologic development of premature infants. N England J of Med 1990; 322:588-93.
Abstract: In a multicenter, randomized clinical trial, we assessed the early neurologic development of 93 children born prematurely whose heart rates were monitored electronically during delivery and compared it with that of 96 children born prematurely whose heart rates were periodically monitored by auscultation. All the children were singletons with cephalic presentation, and all weighed less than or equal to 1750 g at birth. The mental and psychomotor indexes of the Bayley Scales of Infant Development (standardized mean score +/- SD, 100 +/- 16) and a formal neurologic examination were administered at three follow-up visits (at 4, 8, and 18 months of age, corrected for gestational age). At 18 months, the mean mental-development scores in the groups receiving electronic fetal monitoring and periodic auscultation were 100.5 +/- 2.4 and 104.9 +/- 1.8, respectively (P greater than 0.1). The mean psychomotor-development scores in the two groups at 18 months were 94.0 +/- 2.4 and 98.3 +/- 1.8, respectively (P greater than 0.1). The incidence of cerebral palsy was higher in the electronically monitored group--20 percent as compared with 8 percent in the group that was monitored by auscultation (P less than 0.03). In the electronic-fetal-monitoring group (but not in the periodic-auscultation group), the risk of cerebral palsy increased with the duration of abnormal fetal-heart-rate patterns, as assessed by retrospective review (chi 2 trend = 12.71, P less than 0.001). The median time to delivery after the diagnosis of abnormal fetal-heart-rate patterns was 104 minutes with electronic fetal monitoring, as compared with 60 minutes with periodic auscultation. We conclude that as compared with a structured program of periodic auscultation, electronic fetal monitoring does not result in improved neurologic development in children born prematurely.
Leveno KJ, Cunningham FG, Nelson S, et al. A prospective comparison of selective and universal electronic fetal monitoring in 34,995 pregnancies. N Engl J Med 1986:615-9.
Abstract: We investigated the effects of using intrapartum electronic fetal monitoring in all pregnancies, as compared with using it onl in cases in which the fetus is judged to be at high risk. Predominant risk factors included oxytocin stimulation of labor, dysfunctional labor, abnormal fetal heart rate, or meconium-stained amniotic fluid. This prospective alternat-month clinical trial took place over a 36-month period during which 34,995 women gave birth. In alternate months, either 7 (for "selective monitoring) or 19 (for "universal monitoring") fetal monitors were made available in the labor and delivery unit. During the "selective" months, 6420 of 17,409 women (37 percent) were electronically monitored, as compared with 13,956 of 17,586 women (79 percent) during the "universal months."
Universal monitoring was associated with a small but significant increase in teh incidence of delivery by cesarean section because of fetal distress, but perinatal outcomes as assesed by intrapartum stillbirths, low Apgar scores, a need for assisted ventilation of the newborn, admission to the intensive care nursery, or neonatal seizures were not significantly different.
We conclude that not all pregnancies, and particularly not those considered at low risk of perinatal complications, need continuous electronic fetal monitoring duirng labor.
References:Goer, Henci. The Thinking Woman's Guide to a Better Birth. 1999. New York: The Berkley Publishing Group.
Enkin, Keirse, Nilson, Crowther, Duley, Hodnett and Hofmeyr. A guide to effective care in pregnancy and childbirth Third Edition. 2000. Oxford: Oxford University Press.