Labour

Practice EssentialsLabor is a physiologic process during which the fetus, membranes, umbilical cord, and placenta are expelled from the uterus.Stages of laborObstetricians have divided labor into 3 stages that delineate milestones in a continuous process.First stage of labor Begins with regular uterine contractions and ends with complete cervical dilatation at ! cm "ivided into a latent phase and an active phase #he latent phase begins with mild, irregular uterine contractions that soften and shorten the cervix $ontractions become progressively more rhythmic and stronger #he active phase usually begins at about 3%& cm of cervical dilation and is characteri'ed by rapid cervical dilation and descent of the presenting fetal partSecond stage of labor Begins with complete cervical dilatation and ends with the delivery of the fetus (n nulliparous women, the second stage should be considered prolonged if it exceeds 3 hours if regional anesthesiais administered or ) hours in the absence of regional anesthesia (n multiparous women, the second stage should be considered prolonged if it exceeds ) hours with regional anesthesia orhour without it Third stage of labor #he period between the delivery of the fetus and the deliveryof the placenta and fetal membranes "elivery of the placenta often ta*es less than ! minutes, but the third stage may last as long as 3! minutes Expectant management involves spontaneous delivery of theplacenta #he third stage of labor is considered prolonged after 3! minutes, and active intervention is commonly considered +), -ctive management often involves prophylactic administration of oxytocin or other uterotonics .prostaglandins or ergot al*aloids/, cord clamping0cutting, and controlled traction of the umbilical cordMechanism of labor#he mechanisms of labor, also *nown as the cardinal movements,involve changes in the position of the fetus1s head during its passage in labor. #hese are described in relation to a vertex presentation. -lthough labor and delivery occurs in a continuous fashion, the cardinal movements are described as the following 2 discrete se3uences+), 4. Engagement). "escent3. 5lexion&. (nternal rotation6. Extension7. 8estitution and external rotation2. ExpulsionHistory#he initial assessment of labor should include a review of the patient9s prenatal care, including confirmation of the estimated date of delivery. 5ocused history ta*ing should elicit the following information4 5re3uency and time of onset of contractions :tatus of the amniotic membranes .whether spontaneous rupture of the membranes has occurred, and if so, whether the amniotic fluid is clear or meconium stained/ 5etal movements Presence or absence of vaginal bleeding.Braxton%;ic*s contractions must be differentiated from true contractions. #ypical features of Braxton%;ic*s contractions are as follows4 ay start as infre3uently as every !%6 minutes, but usuallyaccelerate over time, increasing to contractions that occur every )%3 minutes #end to last longer and are more intense than Braxton%;ic*s contractions Lead to cervical changePhysical examination#he physical examination should include documentation of the following4 >aternal vital signs 5etal presentation -ssessment of fetal well%being 5re3uency, duration, and intensity of uterine contractions -bdominal examination with Leopold maneuvers Pelvic examination with sterile gloves"igital examination allows the clinician to determine the following aspects of the cervix4 "egree of dilatation, which ranges from ! cm .closed or fingertip/ to ! cm .complete or fully dilated/ Effacement .assessment of the cervical length, which can bereported as a percentage of the normal 3% to &%cm?long cervix ordescribed as the actual cervical length/ Position .ie, anterior or posterior/ $onsistency .ie, soft or firm/Palpation of the presenting part of the fetus allows the examiner to establish its station, by 3uantifying the distance of the body .%6 to @6 cm/ that is presenting relative to the maternal ischial spines,where ! station is in line with the plane of the maternal ischial spines.+),Intrapartum management of laborFirst stage of laborOn admission to the Labor and "elivery suite, a woman having normal labor should be encouraged to assume the position that she finds most comfortable. Possibilities including the following4 Aal*ing Lying supine :itting 8esting in a left lateral decubitus position>anagement includes the following4 Periodic assessment of the fre3uency and strength of uterinecontractions and changes in cervix and in the fetus9 station and position >onitoring the fetal heart rate at least every 6 minutes, particularly during and immediately after uterine contractionsB in most obstetric units, the fetal heart rate is assessed continuously +3,Second stage of laborAith complete cervical dilatation, the fetal heart rate should be monitored or auscultated at least every 6 minutes and after each contraction.+3, Prolonged duration of the second stage alone does not mandate operative delivery if progress is being made, but management options for second%stage arrest include the following4 $ontinuing observation0expectant management Operative vaginal delivery by forceps or vacuum%assisted vaginal delivery, or cesarean delivery.Delivery of the fetusPositioning of the mother for delivery can be any of the following+), 4 :upine with her *nees bent .ie, dorsal lithotomy positionB the usual choice/ Lateral .:ims/ position Partial sitting or s3uatting position On her hands and *neesEpisiotomy used to be routinely performed at this time, but currentrecommendations restrict its use to maternal or fetal indications"elivery maneuvers are as follows4 #he head is held in mid position until it is delivered, followed by suctioning of the oropharynx and nares $hec* the fetus9s nec* for a wrapped umbilical cord, and promptly reduce it if possible (f the cord is wrapped too tightly to be removed, the cord canbe double clamped and cut #he fetus9s anterior shoulder is delivered with gentle downward traction on its head and chin :ubse3uent upward pressure in the opposite direction facilitates delivery of the posterior shoulder #he rest of the fetus should now be easily delivered with gentle traction away from the mother (f not done previously, the cord is clamped and cut #he baby is vigorously stimulated and dried and then transferred to the care of the waiting attendants or placed on the mother9s abdomenThird stage of labor#he following 3 classic signs indicate that the placenta has separated from the uterus+), 4 #he uterus contracts and rises #he umbilical cord suddenly lengthens - gush of blood occurs"elivery of the placenta usually happens within 6%! minutes afterdelivery of the fetus, but it is considered normal up to 3! minutes after delivery of the fetus.Pain control-gents given in intermittent doses for systemic pain control include the following+&, 4 >eperidine, )6%6! mg (C every %) hours or 6!%!! mg (> every )%& hours 5entanyl, 6!%!! mcg (C every hour Dalbuphine, ! mg (C or (> every 3 hours Butorphanol, %) mg (C or (> every & hours >orphine, )%6 mg (C or ! mg (> every & hours-s an alternative, regional anesthesia may be given. -nesthesia options include the following4 Epidural :pinal $ombined spinal%epidural"efinitionLabor is a physiologic process during which the products of conception .ie, the fetus, membranes, umbilical cord, and placenta/ are expelled outside of the uterus. Labor is achieved with changes in the biochemical connective tissue and with gradual effacement and dilatation of the uterine cervix as a result of rhythmic uterine contractions of sufficient fre3uency, intensity, and duration.+, ),Labor is a clinical diagnosis. #he onset of labor is defined as regular, painful uterine contractions resulting in progressive cervical effacement and dilatation. $ervical dilatation in the absence of uterine contraction suggests cervical insufficiency, whereas uterine contraction without cervical change does not meet the definition of labor.:tages of Labor and Epidemiology:tages of LaborObstetricians have divided labor into 3 stages that delineate milestones in a continuous process.5irst stage of labor#he first stage begins with regular uterine contractions and ends with complete cervical dilatation at ! cm. (n 5riedman1s landmar*studies of 6!! nulliparas+6, , he subdivided the first stage into an early latent phase and an ensuing active phase. #he latent phase begins with mild, irregular uterine contractions that soften and shorten the cervix. #he contractions become progressively more rhythmic and stronger. #his is followed by the active phase of labor, which usually begins at about 3%& cm of cervical dilation and is characteri'ed by rapid cervical dilation and descent of the presenting fetal part. #he first stage of labor ends with complete cervical dilation at ! cm. -ccording to 5riedman, the active phase is further divided into an acceleration phase, a phase of maximum slope, and a deceleration phase.$haracteristics of the average cervical dilatation curve is *nown as the 5riedman labor curve, and a series of definitions of labor protraction and arrest were subse3uently established.+7, 2, ;owever, subse3uent data of modern obstetric population suggest that the rate of cervical dilatation is slower and the progression of labor may be significantly different from that suggested by the 5riedman labor curve.+E, F, !,:econd stage of labor#he second stage begins with complete cervical dilatation and ends with the delivery of the fetus. #he -merican $ollege of Obstetricians and Gynecologists .-$OG/ has suggested that a prolonged second stage of labor should be considered when the second stage of labor exceeds 3 hours if regional anesthesia is administered or ) hours in the absence of regional anesthesia for nulliparas. (n multiparous women, such a diagnosis can be made if the second stage of labor exceeds ) hours with regional anesthesia orhour without it.+,:tudies performed to examine perinatal outcomes associated witha prolonged second stage of labor revealed increased ris*s of operative deliveries and maternal morbidities but no differences inneonatal outcomes.+, ), 3, &, >aternal ris* factors associated with a prolonged second stage include nulliparity, increasing maternal weight and0or weight gain, use of regional anesthesia, induction oflabor, fetal occiput in a posterior or transverse position, and increased birthweight.+3, &, 6, 7,#hird stage of labor#he third stage of labor is defined by the time period between the delivery of the fetus and the delivery of the placenta and fetal membranes. "uring this period, uterine contraction decreases basal blood flow, which results in thic*ening and reduction in the surface area of the myometrium underlying the placenta with subse3uent detachment of the placenta.+2, -lthough delivery of the placenta often re3uires less than ! minutes, the duration of the third stage of labor may last as long as 3! minutes.Expectant management of the third stage of labor involves spontaneous delivery of the placenta. -ctive management often involves prophylactic administration of oxytocin or other uterotonics .prostaglandins or ergot al*aloids/, cord clamping0cutting, and controlled cord traction of the umbilical cord. -ndersson et al found that delayed cord clamping .HE! seconds after delivery/ improved iron status and reduced prevalence of iron deficiency at age & months and also reduced prevalence of neonatal anemia, without apparent adverse effects.+E,- systematic review of the literature that included 6 randomi'ed controlled trials comparing active and expectant management of the third stage reports that active management shortens the duration of the third stage and is superior to expectant management with respect to blood loss0ris* of postpartum hemorrhageB however, active management is associated with an increased ris* of unpleasant side effects.+F,#he third stage of labor is considered prolonged after 3! minutes, and active intervention, such as manual extraction of the placenta, is commonly considered.+),Epidemiology-s the childbearing population in the echanism of Labor#he ability of the fetus to successfully negotiate the pelvis during labor involves changes in position of its head during its passage in labor. #he mechanisms of labor, also *nown as the cardinal movements, are described in relation to a vertex presentation, as is the case in F6K of all pregnancies. -lthough labor and delivery occurs in a continuous fashion, the cardinal movements are described as 2 discrete se3uences, as discussed below.+),Engagement#he widest diameter of the presenting part .with a well%flexed head, where the largest transverse diameter of the fetal occiput is the biparietal diameter/ enters the maternal pelvis to a level belowthe plane of the pelvic inlet. On the pelvic examination, the presenting part is at ! station, or at the level of the maternal ischial spines."escent#he downward passage of the presenting part through the pelvis. #his occurs intermittently with contractions. #he rate is greatest during the second stage of labor.5lexion-s the fetal vertex descents, it encounters resistance from the bony pelvis or the soft tissues of the pelvic floor, resulting in passive flexion of the fetal occiput. #he chin is brought into contact with the fetal thorax, and the presenting diameter changesfrom occipitofrontal ..! cm/ to suboccipitobregmatic .F.6 cm/ foroptimal passage through the pelvis.(nternal rotation-s the head descends, the presenting part, usually in the transverse position, is rotated about &6L to anteroposterior .-P/ position under the symphysis. (nternal rotation brings the -P diameter of the head in line with the -P diameter of the pelvic outlet.ExtensionAith further descent and full flexion of the head, the base of the occiput comes in contact with the inferior margin of the pubic symphysis. anagement of Labor5irst stage of labor$ervical change occurs at a slow, gradual pace during the latent phase of the first stage of labor. Latent phase of labor is complex and not well%studied since determination of onset is sub=ective and may be challenging as women present for assessment at different time duration and cervical dilation during labor. (n a cohort of women undergoing induction of labor, the median duration of latent labor was 3E&min with an inter3uartile range of )&!%7!& min. #he authors report that cervical status at admission for labor induction, but not other ris* factors typically associated with cesarean delivery, is associated with length of the latent phase.+3E,>ost women experience onset of labor without premature rupture of the membranes .P8O>/B however, approximately EK of term pregnancies is complicated by P8O>. :pontaneous onset of labor usually follows P8O> such that 6!K of women with P8O> who were expectantly managed delivered within 6 hours, and F6K gave birth within )E hours of P8O>.+3F, $urrently, the -merican $ollege of Obstetricians and Gynecologists .-$OG/ recommends that fetal heart rate monitoring should be used to assess fetal status and dating criteria reviewed, and group B streptococcal prophylaxis be given based on prior culture results or ris* factors of cultures not available. -dditionally, randomi'ed controlled trials to date suggest that for women with P8O> at term, labor induction, usually with oxytocininfusion, at time of presentation can reduce the ris* of chorioamnionitis.+&!,-ccording to 5riedman and colleagues,+7, the rate of cervical dilation should be at leastcm0h in a nulliparous woman and .) cm0h in a multiparous woman during the active phase of labor. ;owever, labor management has changed substantially during the last 3uarter century. Particularly, obstetric interventions such as induction of labor, augmentation of labor with oxytocin administration, use of regional anesthesia for pain control, and continuous fetal heart rate monitoring are increasingly common practice in the management of labor in today1s obstetric population.+&, &), )!, Caginal breech and mid% or high%forceps deliveries are now rarely performed.+&3, &&, &6, #herefore, subse3uentauthors have suggested normal labor may precede at a rate less rapid than those previously described.+E, F, )!,"ata collected from the $onsortium on :afe Labor suggests that allowing labor to continue longer before 7%cm dilation may reduce the rate of intrapartum and subse3uent cesarean deliveries in the L-/ cream was an effective and satisfactory alternative to mepivacaine infiltration for pain relief during perinealrepair. (n a randomi'ed trial of 7 women with either an episiotomy or a perineal laceration after vaginal delivery, women in the E>L- group had lower pain scores than those in the mepivacaine group ..2 @0% ).& vs 3.F @0% ).&B P P .!!!)/, and a significantly higher proportion of women expressed satisfaction with anesthesia method in the E>L- group than in the mepivacaine group .E3.EK vs 63.3KB P P .!/.+76,(n a $ochrane review, -asheim et al suggest that evidence is sufficient to support the use of warm compresses to prevent perineal tears. #hey also found a reduction in third%degree and fourth%degree tears with massage of the perineum to reduce the rate of episiotomy.+77,Pain $ontrolLaboring women often experience intense pain. every )%& hours, fentanyl 6!%!! mcg (C every hour, nalbuphine ! mg (C or (> every 3 hours, butorphanol %) mg (C or (> every & hours, and morphine )%6 mg (C or ! mg (> every & hours.+&, -s an alternative, regional anesthesia may be given. Options are epidural, spinal, or combined spinal epidural anesthesia. #hese provide partial to complete bloc*age of pain sensation below #E%!, with various degree of motor bloc*ade. #hese bloc*s can be used duringlabor and for surgical deliveries.:tudies performed to compare the analgesic effect of regional anesthesia and parenteral agents showed that regional anesthesia provides superior pain relief.+72, &&, 7E, -lthough some researchers reported that epidural anesthesia is associated with aslight increase in the duration of labor and in the rate of operative vaginal delivery,+7F, 2!, large randomi'ed controlled studies did not reveal a difference in fre3uency of cesarean delivery between women who received parenteral analgesics compared with women who received epidural anesthesia+72, 7E, 2!, given during early%stage or later in labor.+2, -lthough regional anesthesia is effective as a method of pain control, common adverse effects include maternal hypotension, maternal temperature N!!.&L5, postdural puncture headache, transient fetal heart deceleration, and pruritus .with added opioids/.+&,"espite the many methods available for analgesia and anesthesiato manage labor pain, some women may not wish to use conventional pain medications during labor, opting instead for a natural childbirth. -lthough these women may use breathing and mental exercises to help alleviate labor pain, they should be assured that pain relief can be administered at any time during labor.- $ochrane review update concluded that relaxation techni3ues and yoga may offer some relief and improve management of pain.:tudies in the review noted increased satisfaction with pain relief and lower assisted vaginal delivery rates with relaxation techni3ues. One trial involving yoga noted reduced pain, increased satisfaction with pain relief, increased satisfaction with the childbirth experience, and reduced length of labor.+2),Of note, use of nonsteroidal anti%inflammatory drugs .D:-("s/ arerelatively contraindicated in the third trimester of pregnancy. #he repeated use of D:-("s has been associated with early closure of the fetal ductus arteriosus in utero and with decreasing fetal renal function leading to oligohydramnios.