There are very few comprehensive evidence-based clinical practice guidelines for management of the second stage of labor; however, the ideal management of the second stage of labor should maximize the probability of vaginal delivery while minimizing the risk of maternal and neonatal morbidity and mortality. The fundamental principles of care in the second stage include: (1) establishing fetal and maternal well-being and fetal head position at the onset; (2) performing hourly vaginal assessments in the second stage by a consistent examiner to assess fetal position and station; (3) informing the primary health care provider when the cervix is fully dilated, if there is a lack of progress in any 1-hour block, and at the end of 2 hours; and (4) regularly assessing the bladder to ensure that a full bladder is not obstructing progress.
Whether to start pushing immediately once full dilation is achieved or to delay pushing to allow for further head descent and rotation is controversial. The practice of delayed pushing is based on the theory that a woman receiving an epidural anesthetic is able to have a period of rest once she reaches 10 cm, thereby allowing the fetus to passively rotate and descend while conserving the patient’s energy for when she starts to push. Previous studies found that delaying maternal pushing for a maximum of up to 2 hours, particularly in primigravidas, reduced the incidence of operative vaginal deliveries and cesarean sections at the expense of an increased duration of second stage. More recent studies in nulliparous women under epidural found that delayed pushing did not significantly improve the likelihood of spontaneous vaginal birth and there was no reduction in the rate of operative vaginal delivery or cesarean section. The risks of delayed pushing include an increased incidence of chorioamnionitis (in one study) when compared to immediate pushing (9.1% vs. 6.6%), postpartum hemorrhage, and umbilical cord pH less than 7.10 (2.7% vs. 1.3%); however, there was no difference in Apgar scores less than 7 at 5 minutes or in NICU admissions. This suggests that a delay in the onset of pushing of more than 1 hour may not be beneficial, and the options/risks of delayed pushing versus immediate pushing should be discussed with nulliparous women with an epidural. A shorter delay while waiting for a dense epidural block to wane may be acceptable for some women who find it hard to push. Few multiparous women were included in the above studies. Their progress in the second stage is generally much quicker.
The Ottawa Hospital utilizes a second stage protocol that allows up to 4 hours total duration of the second stage in primigravidas under epidural and 3 hours for multiparas (Table 16-2). The protocol recommends to wait 2 hours before pushing in all women with epidural anesthesia who have no urge to push, or in whom the station of the presenting part is above +2, or in whom the fetus is in the occipitoposterior (OP) or occipitotransverse (OT) position. If the fetus is in the OP or OT positions, manual rotation to the occipitoanterior (OA) position is attempted and the patient is repositioned to optimize fetal rotation and/or maintain the OA position. After 2 hours, the woman should be instructed to push regardless of head station. The duration of pushing within the total time frame should preferably not exceed 2 hours because the pH of the fetus will gradually fall during active pushing, although absolute time limits cannot be stipulated because of a lack of conclusive evidence.
TABLE 16-2:THE OTTAWA HOSPITAL SECOND STAGE PROTOCOL ||Download (.pdf) TABLE 16-2: THE OTTAWA HOSPITAL SECOND STAGE PROTOCOL
| ||Hour Begins |
| ||1 ||2 ||3 ||4 |
|Primigravida, epidural ||Wait ||Wait ||Wait/push* ||Push |
|Primigravida, no epidural ||Wait ||Wait ||Push || |
|Multigravida, epidural ||Wait ||Wait ||Push || |
|Multigravida, no epidural ||Wait ||Push || || |
Studies show that around 10 to 20 percent of nulliparous women under epidural will have a second stage greater than 3 hours but only 2 percent will exceed 4 hours. There is a lack of consensus to support an absolute time limit to end the second stage with an intervention, and care providers must be aware of the benefits and risks of intervention versus continued expectant management in the second stage.
Recommendations from the National Institute for Health and Care Excellence (NICE) regarding the total duration of the second stage are summarized in Table 16-3. We suggest consideration of operative vaginal delivery at the end of these time limits unless spontaneous delivery is thought to be imminent (i.e., the head is visible and there is continued progress with contractions). In those cases, it is not necessary to impose an absolute limit on the duration of the second stage. There are, however, some important caveats:
The fetus is healthy, term, and in an uncomplicated cephalic presentation
There is no uterine scar (e.g., no previous cesarean section)
The fetal heart, assessed by intermittent auscultation or electronic monitoring, and other tests of fetal well-being are normal and reassuring
There is continued progress as evidenced by gradual descent of the head on hourly assessments
TABLE 16-3:RECOMMENDATIONS FOR DURATION OF THE SECOND STAGE OF LABOR ||Download (.pdf) TABLE 16-3: RECOMMENDATIONS FOR DURATION OF THE SECOND STAGE OF LABOR
|Parity ||Recommendation |
|Nulliparous women || |
Birth would be expected to take place within 3 hours of the start of the active second stage in most women.
A diagnosis of delay in the active second stage should be made when it has lasted 2 hours and a health care professional trained to undertake an operative vaginal birth should be consulted if birth is not imminent.
|Parous women || |
Birth would be expected to take place within 2 hours of the start of the active second stage in most women.
A diagnosis of delay in the active second stage should be made when it has lasted 1 hour and a health care professional trained to undertake an operative vaginal birth should be consulted if birth is not imminent.
If these conditions are not met or if there are concerns about fetal or maternal health, management should be individualized. This usually means shortening the above time parameters or earlier consideration of operative delivery.
Dystocia in the Second Stage
There is no clear consensus on what constitutes delay in the second stage of labor. In general, no change in the head station during any 1-hour interval warrants careful evaluation for dystocia. An active (pushing) phase longer than 2 hours in a primigravida or 1 hour in a multigravida warrants assessment by a health care professional trained in operative vaginal delivery unless birth is imminent. Oxytocin may be started at any time during the second stage, particularly when contractions are inadequate, or there is a lack of progress. Women who are already on oxytocin at the onset of the second stage should continue to receive it provided that there are no concerns regarding the FHR or uterine tachysystole. Assessing fetal position at the start of the second stage of labor, prior to the development of caput and molding, is of paramount importance. Malposition of the fetal head is a frequent cause of delay in the second stage and may be associated with infrequent or insufficient uterine contractions. Failure to determine fetal head position at the start of the second stage can lead to a prolonged second stage, difficulty assessing fetal head position accurately as the second stage progresses, and the inability to perform an operative vaginal delivery if the fetal head position is not known. Maternal positioning and manual fetal head rotations may be important interventions when fetal malposition is identified. In some cases, the fetal head position may be difficult to determine. In these instances, transvaginal ultrasonography, if available, can be helpful in determining head position with great accuracy. If malposition is identified at the start of the second stage, manual rotation to the OA position should be considered in order to avoid a prolonged second stage with lack of fetal descent, progressive worsening of fetal head impaction, and increasing molding and caput formation.
Second stage management should be individualized depending on the clinical situation. In some situations, it may be appropriate to wait longer for spontaneous head rotation, but in other situations, it may be preferable to shorten the timeline for waiting and pushing to avoid the additional complications of a prolonged second stage when operative delivery may be required. Caution should be exercised in the infrequent situation of failure of head descent in a multipara with an occipitoanterior presentation and strong, frequent contractions. This clinical picture may represent true cephalopelvic disproportion, in which the fetus may be significantly larger than in the patient’s previous deliveries. In this case, excessive uterine activity for too long a period could lead to complications. Around 80 percent of multiparas under epidural analgesia will deliver within 3 hours and almost all within 90 minutes without an epidural.
Well-grown fetuses that are not compromised during the first stage of labor and are carefully monitored in the second stage seldom develop asphyxia, even when the second stage is prolonged. One should avoid a traumatic forceps or vacuum delivery just because an arbitrary time point has passed. However, the decision to allow labor to continue should be based on evidence of continued progress of descent or rotation.
Pushing in the Second Stage
During the second stage of labor, the expulsive powers include: (1) involuntary uterine contractions, (2) voluntary efforts of the abdominal, thoracic and diaphragmatic muscles, and (3) action of the levator ani muscles. In general, the more effectively the mother bears down, the shorter the second stage. This action may be more efficient if the woman braces herself against a solid object, such as a hand bar or birthing bars. When the contraction begins, the woman takes one or two deep breaths and then holds her breath to fix the diaphragm. She then pulls on the hand bars (or on her own legs with her hands behind her knees) and at the same time bears down as hard and for as long a period as she can. In general, she should be encouraged not to push beyond the time of completion of each uterine contraction.
Although many obstetrical care providers encourage pushing that incorporates a Valsalva maneuver, the use of “physiologic bearing down” instead of sustained breath holding during expulsive efforts may be equally effective. Physiologic bearing down (making several short pushes without breath-holding, the “open glottis technique”), although resulting in a slightly longer second stage, may result in improved maternal–fetal gas exchange and maternal satisfaction with the birth experience. In general, women should be guided by their own urge to push provided that their pushing efforts are productive. Guided pushing, whereby the birth attendant performs a vaginal exam and depresses the posterior vaginal wall while the patient is pushing to provide guidance and feedback on pushing efforts, may be helpful, particularly when a patient first starts pushing, to establish whether the maternal expulsive efforts are productive and to assess for progress.
Positioning in the Second Stage of Labor
There is no single correct position for delivery. Patients should choose a position that is comfortable for them and enhances their pushing efforts. It has been traditional practice for women to be positioned and to push in the horizontal (dorsal), semi-Fowler’s (head and back elevated at 30 degrees), or lithotomy position during the second stage of labor (Fig. 16-1A to D). Use of these positions is often dictated by interventions such as epidural analgesia, EFM, or intravenous lines and pumps that limit mobility. Upright or vertical positions such as squatting, semi-recumbency, standing, and upright kneeling generate up to 30 percent more intraabdominal pressure and increased anteroposterior and transverse diameters of the pelvic outlet. Positioning may be important when lack of progress is identified in the second stage. Frequent changes in position may help when fetal malposition is identified or to relieve back pain. It is recommended that women should not lie supine or semi-supine during the second stage (in which case a firm wedge should be inserted under the woman’s right side to prevent supine hypotension) and should adopt any other position that is comfortable for her and enhances pushing efforts.
In women with epidural analgesia and especially in women with any degree of motor neuron blockade, appropriate positioning is important to prevent injury associated with lack of sensation, poor alignment, or unnatural positioning of joints (e.g., hyperflexion of hips). Women with epidural anaesthesia do not need to remain horizontal. More upright positions can be used when local anesthetic is combined with narcotics to minimize motor blockade.
Postural Supine Hypotension
Laboring women should avoid supine positioning. When a pregnant, term or near-term woman lies on her back, the uterus bulges over the vertebral column and compresses the inferior vena cava. This leads to an increased blood volume in the lower limbs but decreased return to the heart, lowered pressure in the right atrium, diminished cardiac output, and hypotension. Reduced perfusion of the uterus and placenta leads to fetal hypoxia and changes in the FHR.
Supine hypotension may be exacerbated by an epidural caused by the sympathetic blockade and venous pooling in the lower body. The pregnant woman may not display any signs or symptoms, but significant impairment of uterine blood flow can result. It is important to use a wedge, preferably under the right flank or buttock, for any woman in late pregnancy if she is required to lie supine for delivery or surgery.