The delivery of a full-term newborn refers to delivery at a gestational age of 37-42 weeks, as determined by the last menstrual period or via ultrasonographic dating and evaluation. The aegel rule is a commonly used formula to predict the due date based on the date of the last menstrual period. This rule assumes a menstrual cycle of 2! days and mid-cycle ovulation. "ltrasonographic dating can be more accurate, especially when it is performed early in pregnancy and is used to corroborate or modify a due date based on the last menstrual period.#ppro$imately %%& of singleton pregnancies are delivered preterm and %'& of all deliveries are postterm. Thus, nearly !'& of newborns are delivered at full term, although only 3-(& of deliveries occur on the estimated due date.)%, 2* +ver the past few decades, the number of patients who go into spontaneous labor has decreased, and the percentage of inductions ,iatrogenic labor- has increased to 22& of all pregnancies.)3*.abor and delivery is divided into 3 stages. /n the first stage, the cervi$ dilates as a result of progressive rhythmic uterine contractions. This is typicallythe longest stage of labor. 0ervical effacement, or thinning, occurs throughout the first stage of labor, and is graded '-%''&.o The first stage of labor is divided into the latent and active phases.o The latent phase can last for many hours. The cervi$ dilates, usually slowly, from closed to appro$imately 4-( cm.o The active phase lasts from the end of the latent phase until delivery. /t is characteri1ed by rapid cervical dilation. The cervi$ usually dilates at a rate of %.' cm2h innulliparous women and %.2 cm2h in multiparous women during the active phase. The second stage of labor is the time between complete cervical dilation and delivery of the neonate. This phase lasts minutes to hours. The ma$imum accepted time for the second stage depends on the patient3s parity and whether the patient has an epidural.o 4i$ cardinal movements of labor occur during the second stage of labor. 5ngagement of the head into the lower pelvis 6le$ion of the head, putting the occiput in presenting position 7escent of the neonate through the pelvis /nternal rotation of the verte$ to maneuver past the lateral ischial spines 5$tension of the head to pass beneath the maternal symphysis 5$ternal rotation of the head after delivery to facilitate shoulder deliveryo 4everal clinical parameters are followed. The fetal presentation is determined by the first fetal body part that passes through the birth canal. 8ost commonly, this is the occiput or the verte$ of the head. The fetal station is the relation of the fetal head to the maternal ischial spines. The station is defined as -( cm to 9( cm: ' station is at the level of the ischial spines. The fetal position is the orientation of the fetal verte$ ,the top of the head- in relation to the plane of the maternal ischial spines. The verte$ normally rotates from a transverse position to an anterior or posterior position as the verte$ internally rotates. The delivery of the placenta is the third and final stageof labor: it normally occurs within 3' minutes of delivery of the newborn. #s the uterus contracts, a plane of separation develops at the placenta-endometrium interface. #s the uterus further contracts, the placenta is e$pelled./n ovember 2'%3, the #merican 0ollege of +bstetricians and ;ynecologists ,#0+;- and the 4ociety for 8aternal-6etal 8edicine ,4868- released a committee opinion revising the definition of term pregnancy. The recommended change, as devised by a work group that included representatives from the 5unice term? with the following)4* @ 5arly term@ 37 weeks, ' days, through 3! weeks, A days, of gestation 6ull term@ 3B weeks, ' days, through 4' weeks, A days, of gestation .ate term@ 4% weeks, ' days, through 4% weeks, A days, of gestation Costterm@ #t least 42 weeks, ' days, of gestation/ndicationsormal vaginal delivery of the newborn includes the following circumstances@ 4pontaneous labor mediated by pituitary and placental hormone cascades Dupture of amniotic and chorionic membranes ,suggested by the presence of a watery vaginal dischargeor new oligohydramnios on ultrasonograph- /nduction of labor ,indicated if fetal or maternal medical conditions necessitate delivery-Ehile sporadic contractions may occur, and the cervi$ may begin to soften in anticipation of delivery, the presence of contractions that lead to active cervical change defines labor.ot all vaginal fluid is amniotic fluid, and membrane rupture reFuires confirmation./f the cervi$ is favorable, o$ytocin is given to induce uterine contractions. # favorable cervi$ is defined by the Gishop score, which includes parameters like cervical dilation, softening, effacement, and station. /f the cervi$ is not favorable and no contraindications are present, cervical ripening can be facilitated with intravaginal prostaglandins before o$ytocin is initiated.)(*There are several medications available for cervical ripening. 8isoprostol or prostaglandin 5%,0ytotec- is most often used for cervical ripening. 4ince 2''2, it has been 67# approved for cervical ripening and induction of labor. 7osing is 2(-(' mcg given vaginally, buccally, or sublingually. prostaglandin 52 ,dinoprostone- can also be used for cervical ripening, although it is more e$pensive than misoprostol and has an increased rate of tachysystole ,too many contractions-.)3*# balloon catheter can also be used for ripening. Cennell et al compared 3 methods of ripening the cervi$ in nulliparous women at term and found that the single-balloon catheter offers the best combination of safety and patient comfort. /n a randomi1ed controlled trial, 33' nulliparous women with unfavorable cervices induced at term were treated with % of 3 methods@ double-balloon catheters, single-balloon catheters, or prostaglandin gel.0esarean delivery rates were high with all 3 methods. 4ingle-balloon catheter use was associated with earlier delivery and with significantly less pain@ 3A& of patients had a pain score of H4, vs ((& of patients treated with double-balloon catheteri1ation and A3& of those treated with prostaglandin gel ,P I .''%-. /nduction was complicated by uterine stimulation in %4& of patients in the prostaglandin arm, but none of those in the catheter arms, and mean cord arterial p= was lower in the prostaglandin arm ,7.2( vs 7.2A in the catheter arms )PJ.'('*-.)A*6or more information, see 0ervical Dipening article.0ontraindications4ee the list below@ Ehile most full-term newborns in the "nited 4tates are delivered vaginally, vaginal birth is contraindicated in some circumstances, including those described in this section. 0ord prolapseo Ehen cord prolapse is detected on pelvic e$amination, the clinician should leave the hand in place, applying pressure against the presenting fetal partto keep it as far out of the pelvis as possible to prevent cord compression.o The incidence of cord prolapse is directly proportional to cord length.o The treatment is immediate conversion to cesarean delivery. /f not treated emergently, cord prolapse is associated with high perinatal mortality. Grow presentationo This may convert to face or verte$ presentation and may be managed e$pectantly.o /f the patient is unstable or no conversion occurs,cesarean delivery is recommended. 6ace presentationo 0linicians and mothers may tolerate a trial of e$pectant management, if cephalopelvic disproportion isnot suspected and if the face is in a mentum anterior or mentum transverse position.o /f the face is mentum posterior ,chin facing the maternal sacrum-, a cesarean delivery is reFuired. Greech presentationo "p to (& of all fetuses and %-3& of full-term pregnancies present in the breech position. Clan for abdominal delivery for a footling presentation. 6or frank breech ,ie, hips fle$ed, knees e$tended- and complete breech ,ie, hips and knees fle$ed- presentations detected before the onset of labor, manual pressure maneuvers called e$ternal cephalic version ,50K- may be performed to attempt conversion to a verte$ presentation.o The success rates of 50K are greater than ('& in properly selected patients, but these maneuvers should be performed at term, as they may stimulate labor or result in complications that necessitate prompt delivery.o The #merican 0ongress of +bstetricians and ;ynecologists ,#0+;- recommends abdominal delivery if 50K fails or if a mother in labor presents with breech presentation, as the rates of fetal morbidity and mortalityin these cases are increased with vaginal delivery.)7* 8alpositiono 6etal positions compatible with vaginal delivery are occiput anterior ,+#-, right occiput anterior ,D+#-, and left occiput anterior ,.+#-.o The occiput posterior ,+C- position can be unfavorable for passage through the birth canal. .abor progress should be monitored for progression. /f the fetalstation is high and without descent during labor, change to abdominal delivery should be considered.o 7eep transverse arrest occurs when the fetal head remains in transverse position without descent. "nfavorable maternal pelvic anatomy is the most common cause: abdominal delivery should be considered promptly.o 4houlder presentation is a sign of a transverse fetal lie. /f this presentation is detected prior to active labor, e$ternal rotation through 50K may be attempted. Ehen this presentation is detected during labor, maternal risk for infection, uterine rupture, or both is high. 5mergent abdominal delivery is indicated. Twin pregnancyo /f a nonverte$ second twin presentation occurs, it is managed according to gestational age, maternal preference, and practitioner comfort. The e$ceptions to vaginal delivery include the following@ Cresenting twin in breech position 0onLoined twin anatomy 8ost cases of mono-amniotic twins 4igns of fetal distress or an abnormality that warrants abdominal delivery =igher order birthso /n the "nited 4tates, cesarean delivery is planned for higher order births. Kaginal delivery after cesarean delivery )!*o Ehile safe in most circumstances, vaginal delivery after previous cesarean delivery remains controversial because of the rare but serious complication of uterine rupture. The risk of uterine rupture is appro$imately '.(& in patients who have had one prior low transverse cesarean delivery.o The success rate of this procedure is greater than ('&.o 7uring the delivery, careful fetal and maternal monitoring are needed to detect early signs of dystocia or uterine rupture.o #n in-house anesthesiologist and obstetrician should be available in case complications arise. This type of delivery is not offered in many small hospitals because of the inconsistent availability of anesthesia or operating room staff. This has led to an increase in the cesarean delivery rate to appro$imately 3'& in 2''A.o Kaginal birth after cesarean is contraindicated in cases of multiple prior cesarean deliveries ,M2-, a historyof a classical or T-shaped uterine scar, the presence of placenta previa, the presence of other uterine scars, or concern for true cephalopelvic disproportion. onreassuring fetal heart rate patternso =ospital protocols in the "nited 4tates recommend some form of fetal heart rate monitoring. The need for continuous fetal heart rate monitoring remains unproven in low-risk, full-term pregnancies: however, changes in fetal heart rate monitoring can signal fetal hypo$emia and may indicate the need for emergent abdominal delivery.o 0auses of fetal hypo$emia include placental abruption, placental insufficiency, or a tight nuchal cord. 8ost cesarean deliveries undertaken for suspected fetal distress result in healthy birth outcomes. 8acrosomiao 6etal weight greater than 4'''-4('' g is associated with a higher risk of shoulder dystocia and birth trauma during vaginal delivery.)B*o 8others with diabetes have a higher incidence of macrosomia and risk of shoulder dystocia.o /f the estimated fetal weight is greater than 4('' g in a mother with diabetes, #0+; recommends abdominal delivery.o /f the mother does not have diabetes, abdominal delivery is not recommended until an estimated fetal weight of (''' g. #bnormal placentationo Clacenta previa ,the placenta implanted over the cervical os- is a contraindication to vaginal delivery because of the risk of hemorrhage as the cervi$ dilates.o Clacenta previa complicates up to 2& of all pregnancies. Disk factors include artificial reproductive technology and prior cesarean delivery.o