Tenore, M. Chicago Ave. Reprints are not available from the author. The author indicates that she does not have any conflicts of interest. Sources of funding: none reported. Labor and delivery. Obstetrics: normal and problem pregnancies.
New York: Churchill Livingstone, — American College of Obstetricians and Gynecologists. Induction of labor. Practice bulletin no. Washington, D. Ludmir J, Sehdev HM. Anatomy and physiology of the uterine cervix.
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This content is owned by the AAFP. If labor is active and the pregnancy is at term, a clinician examines the vagina with 2 fingers of a gloved hand to evaluate progress of labor.
If bleeding particularly if heavy is present, the examination is delayed until placental location is confirmed by ultrasonography. If bleeding results from placenta previa, vaginal examination can initiate severe hemorrhage. If labor is not active but membranes are ruptured, a speculum examination is done initially to document cervical dilation and effacement and to estimate station location of the presenting part ; however, digital examinations are delayed until the active phase of labor or problems eg, decreased fetal heart sounds occur.
If the membranes have ruptured, any fetal meconium producing greenish-brown discoloration should be noted because it may be a sign of fetal stress. If labor is preterm 37 weeks or has not begun, only a sterile speculum examination should be done, and a culture should be taken for gonococci, chlamydiae, and group B streptococci.
Cervical dilation is recorded in centimeters as the diameter of a circle; 10 cm is considered complete. Because effacement involves cervical shortening as well as thinning, it may be recorded in centimeters using the normal, uneffaced average cervical length of 3. Station is expressed in centimeters above or below the level of the maternal ischial spines. Fetal lie, position, and presentation are noted. Lie describes the relationship of the long axis of the fetus to that of the mother longitudinal, oblique, transverse.
Position describes the relationship of the presenting part to the maternal pelvis eg, occiput left anterior [OLA] for cephalic, sacrum right posterior [SRP] for breech. Presentation describes the part of the fetus at the cervical opening eg, breech, vertex, shoulder. Women are admitted to the labor suite for frequent observation until delivery. If labor is active, they should receive little or nothing by mouth to prevent possible vomiting and aspiration during delivery or in case emergency delivery with general anesthesia is necessary.
Shaving or clipping of vulvar and pubic hair is not indicated, and it increases the risk of wound infections. An IV infusion of Ringer's lactate may be started, preferably using a large-bore indwelling catheter inserted into a vein in the hand or forearm.
During a normal labor of 6 to 10 hours, women should be given to mL of this solution. The infusion prevents dehydration during labor and subsequent hemoconcentration and maintains an adequate circulating blood volume. The catheter also provides immediate access for drugs or blood if needed. Fluid preloading is valuable if epidural or spinal anesthesia is planned. If instrumental or cesarean delivery seems unlikely, women may drink clear liquids.
Neonatal toxicity can occur because after the umbilical cord is cut, the neonate, whose metabolic and excretory processes are immature, clears the transferred drug much more slowly by liver metabolism or by urinary excretion. Preparation for and education about childbirth lessen anxiety. Physicians are increasingly offering epidural injection providing regional anesthesia as the first choice for analgesia during labor.
Typically, a local anesthetic eg, 0. Initially, the anesthetic is given cautiously to avoid masking the awareness of pressure that helps stimulate pushing and to avoid motor block. Women should be reassured that epidural analgesia does not increase the risk of cesarean delivery 1 Analgesia references Labor consists of a series of rhythmic, involuntary or medically induced contractions of the uterus that result in effacement thinning and shortening and dilation of the uterine cervix.
If epidural injection is inadequate or if IV administration is preferred, fentanyl mcg or morphine sulfate up to 10 mg given IV every 60 to 90 minutes is commonly used.
These opioids provide good analgesia with only a small total dose. If neonatal toxicity results, respiration is supported, and naloxone 0. Clinicians should check the neonate 1 to 2 hours after the initial dosing with naloxone because the effects of the earlier dose abate. If fentanyl or morphine provides insufficient analgesia, an additional dose of the opioid or another analgesic method should be used rather than the so-called synergistic drugs eg, promethazine , which have no antidote.
These drugs are actually additive, not synergistic. Synergistic drugs are still sometimes used because they lessen nausea due to the opioid; doses should be small.
Anesthesiology —, Fetal status must be monitored during labor. The main parameters are baseline fetal heart rate HR and fetal HR variability, particularly how they change in response to uterine contractions and fetal movement.
Because interpretation of fetal HR can be subjective, certain parameters have been defined see table Fetal Monitoring Definitions Fetal Monitoring Definitions Labor consists of a series of rhythmic, involuntary or medically induced contractions of the uterus that result in effacement thinning and shortening and dilation of the uterine cervix.
Several patterns are recognized; they are classified into 3 tiers categories [ 1 Fetal monitoring reference Labor consists of a series of rhythmic, involuntary or medically induced contractions of the uterus that result in effacement thinning and shortening and dilation of the uterine cervix.
A normal pattern strongly predicts normal fetal acid-base status at the time of observation. This pattern has all of the following characteristics:. Early decelerations and age-appropriate accelerations may be present or absent in a normal pattern. An indeterminate pattern is any pattern not clearly categorized as normal or abnormal. Many patterns qualify as indeterminate. Whether the fetus is acidotic cannot be determined from the pattern.
Indeterminate patterns require close fetal monitoring so that any deterioration can be recognized as soon as possible. An abnormal pattern usually indicates fetal metabolic acidosis at the time of observation. This pattern is characterized by one of the following:. Abnormal patterns require prompt actions to correct them eg, supplemental oxygen, repositioning, treatment of maternal hypotension, discontinuation of oxytocin or preparation for an expedited delivery.
Monitoring can be manual and intermittent, using a fetoscope for auscultation of fetal HR. However, in the US, electronic fetal HR monitoring external or internal has become standard of care for high-risk pregnancies, and many clinicians use it for all pregnancies.
The value of routine use of electronic monitoring in low-risk deliveries is often debated. Similar patterns are seen with other effacements.
Reporting cervical effacement as a percentage is oversimplified and does not account for the physiological changes that accompany advancing gestation.
The progressive shortening of the cervix in the third trimester requires the establishment of an arbitrary time 0 at which the cervix is uneffaced. The time chosen will define the length of the original cervix pre-labor and affect subsequent assessments. Differences in cervical length depending on gestational age may also alter preconceived notions examiners have concerning the length of the uneffaced cervix.
Given the inaccuracy of reporting cervical effacement as a percentage, describing actual cervical length in centimeters may be better. Where cervical assessment boards with rings of different dilatations are available for cervical dilatation practice, straight rulers can be used for cervical effacement calibration. The advantage of reporting cervical effacement in centimeters is that the estimate reflects the length of the remaining cervical canal.
No assumptions are made regarding the length of the uneffaced cervix. As a result, reports of cervical effacement would be more consistent. One of the limitations of our study was the possibility that some examiners might have performed more than one cervical exam, which may have skewed the results. However, since data were collected over a 4-year period, it would be unlikely that the results would have been significantly affected.
Another limitation is small sample sizes for some percentages of cervical effacement. In spite of this limitation significant variation in cervical length was still noted for these groups. Strengths of this study were: 1 cervical exams were done by various obstetric clinicians; 2 all transvaginal ultrasound scans were done by one of the authors who did not perform any of the digital cervical exams.
Cervical effacement is the only component of the cervical exam that does not have a point of reference. As a result, the traditional method of reporting cervical effacement as a percentage is unacceptably inaccurate compared to the actual cervical length determined by vaginal probe ultrasound.
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