Testing Modalities (Obstet Gynecol 2009;113:687)

• Fetal mvmt count (“kick count”) (Cochrane Database Syst Rev 2007:CD004909)

Variable protocols, usually 2 h, 3–7× per week

10 mvmts → reassuring; insuff evid to recommend this method of surveillance

• Nonstress test

Continuous fetal heart monitoring × 20–40 min

At least 2 15 bpm × 15 s accelerations (or 10 × 10 at <32 w) → reassuring

Occasional, brief variable decelerations do not affect negative predictive value

Performance for prediction of stillbirth w/i 1 w: Sens 99.7%, spec 45%

• Biophysical profile (From US exam of fetus up to 30 min)

Elements (2 points each if nml/reassuring):

Continuous fetal breathing, 1 episode >30 s

3+ fetal limb or body mvmt

1+ episodes of flexion/extension of a limb or hand

2 × 2 cm or greater pocket of amniotic fluid (or amniotic fluid index >5 cm)

Reactive nonstress test

<6/10 = abn (consider deliv); 6/10 = equivocal (rpt in 6–24 h); >6/10 = reassuring. Prediction of stillbirth w/i 1 w: Sens 99.92%, spec 50%.

• Contraction stress test (oxytocin or nipple stimulation to produce 3 contractions in 10 min of >40 s, w/ continuous FHR monitoring)

Negative = No late or signif variable decelerations

Positive = Late decelerations w/ >50% of contractions

Equivocal = Anything btw “negative” & “positive”

Unsatisfactory = Uninterpretable fetal heart tracing or insuff contraction frequency

Prediction of stillbirth w/i 1 w: Sens 99.96%, PPV 70%

• Umbilical artery Doppler velocimetry (US measurement, only indicated in fetuses w/ growth restriction)

Low resistance system should allow forward flow throughout cardiac cycle

Absent or reverse end-diastolic flow is a/w increased perinatal mortality (5× greater w/ reversed flow) (Lancet 1994;344:1664)

• Middle cerebral artery Doppler velocimetry

US measurement of peak systolic velocity, indicated if concern for fetal anemia

Velocity >1.5 MoM has sens for mod/sev anemia 100%, spec 88% (N Engl J Med 2000;342:9). Optimal screening interval likely 1–2 w

FETAL LUNG MATURITY TESTING BY AMNIOCENTESIS

General Considerations

• Consider testing for planned deliv btw 32 & 39 w

• Before 32 w low likelihood of maturity

• Test performance worsens at earlier GAs

• All tests more accurately predict absence of respiratory distress (w/ mature result) than predict respiratory distress (w/ immature result) (Obstet Gynecol 2001;97:305)

Specific Assays

• Lamellar body count (direct assessment) or optical density at 650 nm (indirect assessment)

>50000/μL or optical density (OD) >0.15 sugg maturity. May vary by institution.

• L/S ratio (L/S about equal till ∼35 w, then lecithin increases)

Threshold value for “mature” varies by institution. Generally mature at >2 (2–3.5)

• PG measurement (appears ∼35 w & rapidly increases)

Quantitative or qualitative measurement. Not affected by mec or bld.

• Foam stability index. Measures functional surfactant. >47 signifies maturity.

• Surfactant/albumin ratio, TDx-FLM II (phased out by manufacturer in 2011)

NEWBORN RESPIRATORY DISTRESS

Epidemiology (Am Fam Physician 2007;76:987)

• 7% of infants. Most common causes: Transient tachypnea of the newborn, respiratory distress syn, mec aspiration syn.

• Less common causes: Delayed transition, infxn, persistent pHTN, PTX, nonpulmonary causes (anemia, CHD)

Signs and Symptoms

• Tachypnea (>60 breaths/min), nasal flaring, poor feeding, grunting, sub- or intracostal retractions, insp stridor, apnea, cyanosis

Transient Tachypnea of the Newborn

• >40% of cases of respiratory distress

• Inadeq fluid clearance from lung → decreased pulm compliance → tachypnea

• Onset w/i 2 h of birth; usually resolves in <72 h

• CXR: Diffuse parenchymal infiltrates

Respiratory Distress Syndrome (Hyaline Membrane Disease)

• Affects 24000 infants in US annually

Most common before 28 w gest

1/3 of infants 28–34 w gest

<5% of infants after 34 w gest

• Surfactant deficiency causing atelectasis & V/Q mismatching → hypoxemia

• Incid ↑ for newborns of diabetic moms

• CXR: Homogenous, opaque infiltrates, & air bronchograms

Meconium Aspiration Syndrome

• Mec-stained amniotic fluid = 15% of deliveries → 10–15% of those get mec aspiration syn; mec = irritative, obstructive, medium for bact culture

• Usually term or postterm infants; signif respiratory distress immediately after deliv

• CXR: Patchy atelectasis or consolidation

General Management

• Diagnostic CXR; CBC, bld gas, bld cx

• Supplemental oxygen therapy, w/ assisted ventilation if necessary

• Supportive care w/ fluid/electrolyte mgmt & neutral thermal environment

Oral feeding often withheld w/ respiratory rate >80 breaths/min

• Empiric ampicillin & gentamicin if risk factors for sepsis or refrac/persistent sx

• Surfactant administration may be req

GROUP B STREPTOCOCCAL DISEASE

Definition and Epidemiology (MMWR 59(RR10):1)

• Intrapartum vertical transmission of GBS is the leading cause of infectious morbidity/mortality in neonates; incid is ∼0.35/1000 births

• Caused by GBS infxn of fetal mucosal surfaces by GBS in amniotic fluid or birth canal

• 10–30% of pregnant women are colonized w/ GBS in GI tract or vagina

• Risk factors for invasive perinatal dz include:

<37 w at deliv

Ruptured amniotic membranes for >12 h

Intra-amniotic infxn

Young mat age

Black race

Low levels of anti-GBS Ab

Clinical Manifestations

• Sepsis, PNA, & meningitis in the 1st w of life

• Fatal in 2–3% full-term infants & 20–30% of preterm newborns <33 w GA

Screening and Diagnosis

• Pregnant women should routinely be screened by rectovaginal swab at 35–37 w. Culture results are valid for up to 5 w, then should be repeated at >5 w.

• NAAT for GBS is currently only indicated in women w/ (1) culture data unk, (2) at term, & (3) w/o prolonged rupture of membranes or fever

Treatment

• Intrapartum Abx indicated for:

Positive rectovaginal culture during this Preg

GBS bacteriuria at any time during this Preg (exempt from routine screening)

H/o perinatal GBS dz in a prior Preg (exempt from routine screening)

Culture data unavailable & <37 w OR term w/ rupture of membranes >18 h or temperature >100.4°F

• Intrapartum ppx NOT indicated at the time of cesarean deliv at any GA for women delivered prior to labor w/ intact membranes

SPONTANEOUS LABOR AND DELIVERY

Definitions

• Labor: Regular uterine contractions & cervical change

• 1st stage of labor: Onset of labor → full cervical dilation

Latent phase: Early labor until acceleration of rate of cervical change

Active phase: Period of accelerated cervical change until full dilation

Historically, minimum rate of cervical change: Nulliparas ∼1.2 cm/h, multiparas, ∼1.5 cm/h (N Y Acad Med 1972;48:842)

Labor curve: Friedman (1955) described ideal labor progress at term; Zhang (2002) showed women enter active phase at 3–5 cm, w/ variable labor course & no deceleration phase

• 2nd stage of labor: Full cervical dilation → deliv of the infant

Consider 2nd stage arrest in nulliparas after 2 h (no epidural) or 3 h (w/ epidural), or in multiparas after 1 h (no epidural) or 2 h (w/ epidural)

• 3rd stage of labor: Deliv of the infant → deliv of the placenta

• 4th stage of labor: 1–2 h immediately following deliv of the placenta

• Cervical assessment: Cervical dilation is measured in cm. Cervical effacement is documented as percentage of full length (4 cm) cervix lost (0% is full length & 100% is paper thin), or as cm of length. Fetal station is descent of the bony fetal presenting part in centimeters above or below the mat ischial spine (−5–+5 cm scale).

• Fetal position: Orientation of the presenting part relative to the mat pelvis

Cephalic presentation w/ occiput documented on mat left/right, rotated post/anter/transverse (eg, ROA). The sacrum may be used for fetuses in breech presentation, the acromion for transverse lie, the mentum for face presentations

Cardinal Movements of Labor

• Engagement: Passage of widest diameter of presenting part below pelvic brim

• Descent: Passage of presenting part downward into pelvis

• Flexion: Allows optimal descent by presenting smallest cranial diameter

• Internal rotation: Mvmt of the fetal head from transverse to anteroposterior

• Extension: Mvmt of the fetal head under the pubic symphysis & out the introitus

• External rotation (“restitution”): Mvmt of the head to align w/ torso

• Expulsion: Deliv of the fetal body

Management of Labor

• Physical exam on presentation: Mat VS; cervical dilation, effacement, fetal station, rupture of membranes (± mec), presence of vaginal bleeding, & estimated fetal weight (by Leopold’s)

Fetal heart assessment (intermittent in low-risk, or continuous in high-risk pts) & uterine tocometry to assess fetal status & contractions

• Consider CBC, bld type & screen, urinalysis

• IV access, avoid solid foods (Obstet Gynecol 2009;114:714)

• Walking & upright positioning in early labor may ↓ the 1st stage by 1 h (Cochrane Database Syst Rev 2009,2:CD003934)

• Assess desire for pain control, w/ or w/o regional anesthesia

• GBS ppx if indicated

Management of Delivery

• Pushing may begin w/ full cervical dilation or be delayed until presenting part descends (“laboring down”); pushing generally accompanies contractions. Delayed pushing ↑ length of the 2nd stage by ∼1 h, but ↓ the need for instrumented deliveries (but not cesarean deliveries) (J Obstet Gynecol Neonatal Nurs 2008;37:4). Pushing should not be delayed if there is an indication to expedite deliv (eg, infxn).

• No indication for routine episiotomy. If necessary, midline a/w ↓ bld loss & ↑ anal sphincter injury compared to mediolateral.

• Warm compresses to the perineum may ↓ incid of 3rd/4th-degree lacerations (Cochrane Database Syst Rev 2011;12:CD006672)

• In women w/o epidural anesthesia, pushing while upright was a/w ↑ risk of EBL >500 cc & ↓ abn FHTs w/o signif impact on length of 2nd stage (Cochrane Database Syst Rev 2012;5:CD002006)

• Deliv of the fetal head:

Care should be taken to control speed of deliv & to protect the anter vaginal wall, urethra, & clitoris

The perineum should be eased over the fetal head

The head should be allowed to restitute

Gentle downward traction of the head to deliver the anter shoulder (difficulty w/ this maneuver should prompt consideration of shoulder dystocia)

The body should be delivered w/ gentle upward traction, supporting the perineum as poss

• The cord should be clamped & cut → delayed cord clamping ↓ risk of fetal/neonat anemia, but ↑ need for phototherapy (Cochrane Database Syst Rev 2008:CD004074; BMJ 2011;343:d7157). Delaying cord clamping by 45 s in premature infants <37 w may ↓ risk of IVH & neonat xfusion (Cochrane Database Syst Rev 2004;4:CD003248)

• Active mgmt of 3rd stage w/ suprapubic pres & controlled cord traction may ↓ mat hemorrhage (Cochrane Database Syst Rev 2011;11:CD007412)

• Consider deliv onto mat abd to promote immediate breastfeeding & bonding (Cochrane Database Syst Rev 2012;5:CD003519)

• Give oxytocin in the 3rd stage to ↓ postpartum hemorrhage (Cochrane Database Syst Rev 2001;(4):CD001808)

• Inspect the placenta to identify anomalies & to ensure intact disc

• Fetal cord bld gas analysis & postpartum hemorrhage (see sections below)

INDUCTION OF LABOR (IOL)

Definition and Epidemiology

• Stimulation of uterine contractions w/ intent to cause vaginal deliv prior to spontaneous onset of labor

• 23.2% of births in 2009 were after IOL (National Vital Statistics Report, 2011)

• “CR” is the softening, thinning, & dilating to facilitate successful IOL

Indications

• Risks (to mother or fetus) of continuing Preg outweigh the risks a/w effecting deliv, & no contraindication to vaginal birth

• Labor should not be electively induced prior to 39 w gest due to significantly elevated neonat morbidity

• Overall, multiparas are less likely than primiparas to fail induction or require cesarean deliv at a given Bishop Score

Methods of Cervical Ripening & Induction of Labor

• Oxytocin – most commonly used induction agent

Various dosing regimens; titrate to contractions q2–3min

Low-dose regimen (start 0.5–2 mU/min w/ 1–2 mU/min ↑ q15–40min)

High-dose regimen (start 6 mU/min w/ 3–6 mU/min ↑ q15–40min)

Note: High-dose regimen decreases time to deliv, but increases rate of tachysystole w/ FHR changes (Cochrane Database Syst Rev 2012;3:CD001233)

• Misoprostol (PGE1) – for CR or IOL

Oral misoprostol superior to vaginal misoprostol for CR/IOL (fewer 5-min Apgars <7)

Dosage 25 mcg PO q2h or 50 mcg PO q4h (Cochrane Database Syst Rev 2006;(2):CD001338)

Vaginal misoprostol may be used for CR/IOL at dose of 25 mcg PV q3–6h

Contraindicated if h/o uterine Surg (including prior cesarean) given elevated risk of uterine rupture

• Dinoprostone (PGE2) – for CR or IOL

Each insert contains 10 mg of dinoprostone → releases mean dose of 0.3 mg/h

Dosed q12h

Upon removal of insert, quickly eliminated from mat circulation

• Amniotomy alone (Cochrane Database Syst Rev 2000;(4):CD002862)

Insuff evid regarding efficacy

↑ need for oxytocin augmentation vs. vaginal prostaglandin

• Balloon catheter (Cochrane Database Syst Rev 2012;3:CD001233) – for CR or IOL

Placement of balloon catheter w/ 30–60 cc of saline through internal os into extra-amniotic space

↓ efficacy for multiparous women & ↓ risk of tachysystole compared w/ prostaglandin

• Membrane stripping (Cochrane Database Syst Rev 2005;(1):CD000451)

Manual detachment of inferior pole of fetal membranes during vaginal exam

• Sexual intercourse: Insuff evid. Likely ineffective (Obstet Gynecol 2007;110(4):820–826; Cochrane Database Syst Rev 2001;(2):CD003093).

• Breast stimulation: Decreased postpartum hemorrhage compared to no intervention. No difference in rates of cesarean when compared to no intervention or oxytocin. Not effective in women w/ unfavorable cervix (Cochrane Database Syst Rev 2005;(3):CD003392).

Complications of Induction

• Tachysystole (greater than 5 contractions in 10 min). Rx: Stop/↓ uterine stimulation, consider tocolysis

• Uterine tetany (contraction lasting greater than 2 min). Rx: Stop/↓ uterine stimulation, consider tocolysis

• Cord prolapse (w/ amniotomy). Rx: Cesarean deliv.

• HoNa (w/ extended infusion of oxytocin). Rx: Stop oxytocin infusion, consider free water restriction, recheck, & resume.

• Cesarean deliv ↑ compared to spontaneous labor, but elective IOL at 41+ w, compared w/ expectant mgmt may ↓ c-section (Cochrane Database Syst Rev 2012;6:CD004945)

INTRAPARTUM FETAL MONITORING

Background

• Justification for intrapartum FHR monitoring based on expert opinion & medicolegal precedent

• Continuous FHR monitoring a/w (1) reduction in neonat seizures, w/o significant differences in cerebral palsy, infant mortality or other std measures of neonat well-being; & (2) ↑ in cesarean deliv & instrumental vaginal births when compared to intermittent auscultation or no monitoring (Cochrane Database Syst Rev 2006;3:CD006066)

Methods of Monitoring

• FHR: External via Doppler US -or- internal via fetal scalp electrode

• Contractions:

External pres transducer (qualitative)

Intrauterine pres catheter (quantitative). Measurement in MVU: Add up peak minus baseline uterine pres for each contraction over 10 min; >200 MVU considered adequate for labor (Obstet Gynecol 1986;68:305).

Definitions (Obstet Gynecol 2008;112:661)

• Baseline: Avg FHR, exclusive of accelerations, decelerations, & marked variability, taken over a 10-min interval, rounded to nearest 5 bpm

Tachy: Baseline > 160 bpm

Brady: Baseline < 110 bpm

• Variability: Beat-to-beat fluctuations in the baseline FHR, exclusive of accelerations & decelerations. Measured from peak to trough of rapid fluctuations.

Absent: Amplitude undetectable

Minimal: Amplitude btw 1 & 5 bpm

Mod: Amplitude btw 6 & 25 bpm

Marked: Amplitude > 25 bpm

• Accelerations: Increased FHR ≥15 bpm for ≥15 s (before 32 w, use ≥10 bpm & ≥10 s). Time from baseline to peak HR is <30 s. Prolonged acceleration lasts 2–10 min.

• Decelerations: ↓ in FHR

Early deceleration: Nadir w/ peak of contraction. Baseline to nadir takes >30 s.

Late deceleration: Nadir after peak of contraction. Baseline to nadir >30 s.

Variable deceleration: ↓ ≥15 bpm from baseline lasting at least 15 s. Baseline to nadir <30 s.

Prolonged deceleration lasts 2–10 min

Sample Fetal Heart Tracings