Pathophys: (Nejm 1999;341:660)

60% go into labor between 39 and 41 weeks; rare to go more than 300 d unless anencephaly

Sx: Rhythmic pains radiate to small of back; bloody show; ruptured membranes with positive ferning and/or nitrazine paper testing

Si:Cervical effacement and dilatation. Presentations: vertex (96%), breech (4%), transverse lie and mental (<1%)

Stage I: Onset of labor to full dilatation of cervix; usually 4-12 h

Stage II: Complete dilatation to infant delivery, median duration 50 min in nullips, 20 min in multips

Stage III: Infant delivery until placental delivery, usually 5-15 min

Many, esp preeclampsia, abruption, stillbirth, and fetal growth retardation, assoc w undetected clotting factor mutations, eg, Factor V Leiden (Nejm 1999;340:9)

• Endometritis
• Failure to progress, caused by cephalopelvic disproportion, or overmedication
• Mortality: maternal = 3-4/10 000; infant/perinatal = 3.5%, 2% stillborn, rates increased 3× in breech
• Perineal lacerations:
• 1st degree: Superficial
• 2nd degree: Tissue injury sparing rectal sphincter
• 3rd degree: Partial or complete separation of rectal sphincter
• 4th degree: Tear into rectum; even w good repair, many (>1/2?) 3rd- and 4th-degree lacerations pts have long-term fecal incontinence, esp if episiotomy or forceps used (Nejm 1993;329:1905)
• Premature labor, often due to bacterial chorioamnionitis (Nejm 2000;342:1500); due to short "incompetent" cervix predictable by transvaginal US @ 24-28 WK (Nejm 1996;334:567)
• Premature rupture of membranes (PROM), >1 h before onset of labor; w/u w sterile speculum exam and tests of vaginal fluid for ferning and nitrazine positivity, check fetal lung maturity (eg, L/S ratio) if <36 wk, grp B strep chlamydia and gc cultures; rx (see below)
• Prepartum bleeding in 3rd trimester: Do digital exam of cervix only after ultrasound or set up to do immediate C/S because may be PLACENTA PREVIA, 1/150 deliveries, increases w maternal age and h/o previous praevia; caused by low implantation of placenta so it partially covers cervical os; those discovered in early pregnancy by ultrasound often migrate away by 3rd trimester; PLACENTAL ABRUPTION(Jama 1999;282:1646), associated w HT and trauma but most are spontaneous, usually painful unlike praevia; can cause uterine enlargement and tenderness, fetal distress, maternal shock, rx by delivery; VASA PREVIA, cord vessels scattered throughout membranes, 1/100 antepartum bleeders, pulsatile vessels at cervical os
• Presentation, abnormal: Breech; rx w external cephalic version after 35 wks; moxibustion w herbs and acupuncture? (Jama 1998;280:1580) at 33 wk
• Postpartum bleeding in mother: Increased by aspirin use within 5 d of delivery (Nejm 1982;307:909); 1st examine for laceration or retained placenta, then oxytocin 10 U im or in dilute iv soln, eg, 10-30 U/1000 cc (not iv push), then vigorous bimanual massage of uterus, then methylergonovine (Methergine) 0.2 mg im (not iv), then 15-methyl prostaglandin E₂ (Hemabate) 250 mg im, may repeat in 15-90 min, then hysterectomy or hypogastric artery ligation
• Pulmonary embolus in 1/4000, a 10× increase over baseline
• Shoulder dystocia; rx see below
• Urinary incontinence in mother subsequently incr from 10% prevalence in nullips to 16% post-C/S, and 21% postvaginal deliveries (Nejm 2003;348:900); true for breeches too (Jama 2002;287:1822)

Lab:

Chem:Amniotic fluid to test for lung maturity, if may be premature; false positives in diabetics

Noninv:

• Nonstress test (NST) for fetal movement and heart rate; oxytocin challenge stress test or nipple stimulation produces 3 or more contractions in 10 min to measure effect on fetal heart rate
• Biophysical profile by ultrasound; calculate by scoring 0 if absent and 2 if present for fetal breathing movements, gross fetal body movements, fetal tone, reactive NST, and amniotic fluid volume in 1 pocket or total cm in each quadrant (amniotic fluid index) 2 cm; last 2 most important; 8/10 score is good (Am J Obgyn 1987;156:527)
• Fetal monitoring usually used in most deliveries now although abnormalities correlate w an already injured fetus and does not prevent cerebral palsy (Obgyn 1995;86:613); repetitive late decels and decr variability both are assoc w a 2.5-3.5 3 incr incid of CP but 99.8% false-pos rate (Nejm 1996;334:613); if use in all you increase C/S rate without any improvement in outcome (Nejm 1986;315:615); similarly, interval monitoring and fetal pulse oximetry do not decr C/S rate or adverse peripartum outcomes (Nejm 2010; 362;306; 2006;355:2195)

Xray:Ultrasound, for gestational age, or for amniocentesis for fetal maturity if premature labor

Rx:

Avoid peripartum ASA (Nejm 1982;307:909); and bupivacaine 0.75% for epidural or paracervical blocks since causes cardiac arrests, hard to resuscitate (FDA Drug Bull 1983;13:23)

Analgesia possible w local paracervical blocks, spinal, and/or continous epidural blocks (rv—Nejm 2003;348:319), which may impairs ability to walk but can be done before >4 cm dilatation and does not incr operative delivery rate (Nejm 2005;352:655)

Episiotomy does more harm than good (Jama 2005;293:2141); perineal massage in last 5 weeks pregnancy reduces incidence (Cochrane Database Syst Rev 2006;[1]:CD005123)

Spontaneous vaginal delivery; amniotomy (rupture of membranes) at 3+-cm dilatation speeds labor by >2 h safely (Nejm 1993;328:1145); walking during early labor has no effect (Nejm 1998;339:76)

Vaginal birth after C/S (VBAC) successful in 60-80% if previous low horizontal incision; but ability to predict which pts works best in is difficult (Nejm 1996;335:689); cmplc: uterine rupture (Nejm 2001;345:3) in 0.8% w/o but 2.5% w prostaglandin induction, compared to 0.15% if do repeat C/S and never goes into labor; infant hypoxic damage rates higher, endometritis and need for transfusions (Nejm 2004;351:2581)

Cesarean sections: Current increase to 25% of all deliveries is fueled to some extent by "repeats" (Nejm 1984;311:887) but also by individual physician practice styles (Nejm 1989;320:706); in Ireland still only 5% C/S rate and perinatal mortality as good as US (Obgyn 1983;61:1); "active management of labor" by amniotomy within 1st h and pitocin at 6-36 mU/min to keep q2min contractions reduces C/S by 30% (Nejm 1992;326:450) vs no reduction in C/S rate though labor duration decr × 2 h plus less maternal fever (Nejm 1995;333:745). All repeat sections should be delayed until 39 wk to minimize neonatal cmplc (Nejm 2009;360:111)

of PROM (pathophys rv—Nejm 1998;338:663), w watching only vs induction w pitocin + protaglandin E (Nejm 1996;334:1005, 1053), antibiotics if fever, fetal tachycardia, pos grp B strep culture, if lasts >12-18 h

of threatened premature delivery from PROM, premature labor, or preeclampsia (Jama 1995;273:413): -methasone 12 mg im × 2, 24 h apart, or dexamethasone 6 mg im q 6-12 h × 4 once (Jama 2001;286:1581), between 24-34 wk gestation to reduce fetal risk of hyaline membrane disease and intraventricular hemorrhage

of premature labor, <34 wk (Nejm 2007;357:477):

• 1st: MgSO₄ 4 gm iv over 20 min, then 2 gm/h iv/im follow Mg levels, 5-7 mg/cc is therapeutic range (Clin Obgyn 1990;33:502), overdose can cause fatal respiratory depression;
• 2nd: Terbutaline or isoxsuprine (Ritodrine), but only delays delivery by 24-48 h without improving survival, so use to buy time to transport or get steroids on board (Nejm 1992;327:308, 349); adverse effects: elevate blood sugar, cardiovascular risks, esp pulmonary edema (Ann IM 1989;110:714)
• 3rd: Nifedipine 10 mg sl up to 40 mg/h then 20 mg q 6 h maintenance, safer than Ritodrine (Am J Obgyn 1990;163:105) but may impair uteroplacental bloodflow; or
• Hydroxyprogesterone caproate (Makena) in those with prior PTB (Am J Obstet Gynecol 2006;194:1234, Nejm 2003;348:2379), esp w short cervix by US (Nejm 2007;357:462); 15-20 injections, initiation at 21 weeks as good as at 16 weeks (Am J Obstet Gynecol 2007;197:260); $690 per injection
• Indomethacin also works but infant cmplc's not worth it (Nejm 1993;329:1602)

of shoulder dystocia, all within 5 min:

• 1st, legs up (McRobert’s maneuver)
• 2nd, suprapubic pressure
• 3rd, Wood’s screw maneuver or disimpact anterior shoulder, or Rubin’s maneuver, in which fetal shoulder is rotated toward its chest; typically McRoberts accompanies Wood’s or Rubin’s to enhance chances of success.
• 4th, episiotomy
• 5th, remove posterior shoulder, fracture clavicle
• 6th, Cesarean section

of failure to progress: risk of neonatal intracranial bleed or other damage elevated by use of forceps, vacuum, or C/S, so none preferable over the others (Nejm 1999;341:1709)