Interpretation of FHR variability from external tracing appears to be more reliable when using a second-generation fetal monitor than when using a first-generation monitor.3 Loss of variability can be simple and may be the result of fetal rest (rest-activity cycle or behavioral state), with variability usually increasing spontaneously within 30 to 40 minutes.19 An uncomplicated loss of variability can also be caused by sedatives of the central nervous system, such as .B. morphine, diazepam (valium) and magnesium sulfate; parasympatholytics such as atropine and hydroxyzine (Atarax); and centrally acting adrenergic agents such as methyldopa (Aldomet) at clinical doses.19 Longer delays may be caused by any mechanism that can normally lead to periodic or episodic delays, but the return to baseline is delayed because the stimulus or mechanism causing the delay is not reversed. This is often associated with hypoxia. Mechanisms that are less likely to resolve spontaneously are therefore more likely to be associated with prolonged slowdowns, such as umbilical cord compression, hypotension or deep hypoxemia of the mother, tetanus uterine contractions, or prolonged head compression associated with the second phase of labor. An FHR greater than 100 beats/min with good variability is tolerable, but a longer delay of less than 100 beats/min requires an immediate effort of dissolution and a fall below 60 beats/min becomes an obstetric emergency, as it is almost always associated with fetal hypoxia. In addition to monitoring fetal heart rate patterns, information about the effects of labor on the fetus can also be obtained by observing the pattern of uterine contractions. Models of uterine contraction can provide information about the progress of labor. Because uterine contractions can affect placental exchange, evaluating contraction patterns can provide clues about the potential effects of contraction rate and force on the fetus. Electronic fetal heart rate monitoring is often used to assess the well-being of the fetus during labour. While detecting fetal compromise is an advantage of fetal monitoring, there are also risks, including false positive tests, that can lead to unnecessary surgery.
Since variable and inconsistent interpretation of fetal heart rate monitoring can affect management, a systematic approach to model interpretation is important. The fetal heart rate is constantly and meticulously adjusted in response to the environment and stimuli of the fetus. Fetal heart rate patterns are classified as calming, unsoothing, or threatening. Non-calming patterns such as fetal tachycardia, bradycardia and late slowdowns with good short-term variability require intervention to exclude fetal acidosis. Worrisome patterns require intrauterine fetal resuscitation and immediate delivery. The distinction between a soothing and non-soothing fetal heart rate pattern is the essence of an accurate interpretation that is essential for proper triage decisions. Internal cardiotocography uses an electronic transducer directly connected to the fetus. A metal electrode, sometimes called a spiral or scalp electrode, is attached to the fetal scalp through the cervical opening and connected to the monitor. Internal monitoring allows for more accurate and consistent transmission of fetal heart rate because, unlike external monitoring, it is not affected by factors such as movement.
Internal monitoring may be used where external monitoring is insufficient or where closer monitoring is required. [6] Internal tocumetry can only be used when the amniotic sac is ruptured (spontaneously or artificially) and the cervix is opened. To measure the strength of the contractions, a small catheter (called an intrauterine pressure catheter or UIC) is passed beyond the fetus into the uterus. Combined with an internal fetal monitor, an IUPC can provide a more accurate reading of the baby`s heart rate and the strength of contractions. [Citation needed] 8. Vintzileos AM, Nochimson DJ, Guzman ER, Knuppel RA, Lake M, Schifrin BS. Intrapartum electronic monitoring of fetal heart rate versus intermittent auscultation: a meta-analysis. Obstet Gynecol.
1995;85:149–55. A normal contraction pattern is shown in the image above with contractions every 2-3 minutes. Electronic fetal monitoring creates a display on a computer screen or paper graph that records the heart rate and contractions of the fetus. In the image above, you can see the fetal heart rate marked with the blue indicator. The contractions are red. Electronic fetal monitoring uses special devices to continuously measure your baby`s heart rate response to contractions. This way, your doctor can assess how your baby is handling labor. 4. Fetal heart rate patterns: monitoring, interpretation and management.
ACOG Technical Bulletin No. 207. Washington, D.C.: ACOG, 1995. When you look at the screen, the fetal heart rate is usually at the top and the contractions at the bottom. When the machine prints graphic paper, you will see the fetal heart rate on the left and contractions on the right. .
