Pocket ObGyn – Spontaneous Labor and Delivery
See Abbreviations
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 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
Figure 10.2 Labor curves
(Reprinted with permission from Zhang J, Troendle JF,Yancey MK. Reassessing the labor curve in nulliparous women.
Am J Obstet Gynecol. 2002;187:824)
| Median [and 95%ile] hours in labor (4–10 cm) | ||
| Nulliparas | Multiparas | |
| Spontaneous labor | 3.8 [11.8] | 2.4 [8.8] |
| Induced labor | 5.5 [16.8] | 4.4 [16.2] |
| Active phase (6–10 cm) was similar amongst all groups, w/ median ~1 h | ||
| From Harper LM, Caughey AB, Odibo AO, et al. Normal progress of induced labor. Obstet Gynecol. 2012;119(6):1113–1118. doi:10.1097/AOG.0b013e318253d7aa. | ||
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 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 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)
Definition and Epidemiology
- Stimulation of uterine contractions w/ intent to cause vaginal deliv prior to spontaneous onset of labor
- 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
| Simplified Bishop Score for determining successful IOL | ||||
| Points scored | 0 | 1 | 2 | 3 |
| Dilation (cm) | 0 | 1–2 | 3–4 | ³5 |
| Station | -3 | -2 | -1 or 0 | +1 or +2 |
| Effacement (%) | 0–30 | 40–50 | 60–70 | ³80 |
| Total score: Successful IOL (sens/spec)
>4: 59.2/67.9 >5: 40.6/82.6 >6: 18.8/94.2 Note: Cervical consistency (firm, soft) & position (anter, post) are included in the “full” Bishop Score, but do not add predictive power beyond the simplified score above |
||||
| From Laughon SK, Zhang J, Troendle J, et al. Using a simplified Bishop score to predict vaginal delivery. Obstet Gynecol. 2011;117(4):805–811. doi:10.1097/AOG.0b013e3182114ad2. | ||||
- 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 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 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
- 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 wellbeing; & (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 -orinternal 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 & 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 ³15 bpm for ³15 s (before 32 w, use ³10 bpm &
³10 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: ¯ ³15 bpm from baseline lasting at least 15 s. Baseline to nadir <30 s.
Prolonged deceleration lasts 2–10 min
| Fetal heart tracings in labor | ||
| Category | Definition | Interpretation |
| I | Baseline FHR btw 110 & 160
• w/ mod variability • w/o late or variable decelerations • w/ or w/o accelerations • w/ or w/o early decelerations |
Nml & requires no additional action. Accelerations (particularly >2 in 30 min) are highly predictive of favorable fetal acid–base status (Am J Obstet Gynecol 1982;142:297; Am J Obstet Gynecol 1979;134:36). |
| II | Any tracing not Category I or Category III | Indeterminate significance & requires close follow-up.Trial of supportive measures reasonable (see Category III). |
| III | Absent variability w/
• late decelerations during >50% of contractions over 20 min, or • variable decelerations w/ >50% of contractions over 20 min or brady OR • sinusoidal pattern (sine wave-like pattern in FHR baseline w/ a frequency of 3–5/min, persisting for 20 min) |
Abn & requires immediate eval. Initial intrauterine resusc:
• Change mat position • Administer mat oxygen • D/c labor stimulation • Consider tocolytics • Correct mat HoTN or compromised placental perfusion If supportive measures fail to correct the Category III pattern, deliv may be indicated. |
Sample Fetal Heart Tracings
Figure 10.3 Fetal heart rate variability
(Revised and reprinted with permission from Menihan CA, Kopel E. Electronic Fetal Monitoring: Concepts and Applications. 2nd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2007)
Figure 10.4 Fetal heart rate accelerations and decelerations
| Early Deceleration
nadir of early deceleration
peak of contraction
start of end of contraction contraction |
(continued)
Figure 10.4 (Continued )
(Revised and reprinted with permission from Menihan CA, Kopel E. Electronic Fetal Monitoring: Concepts and Applications. 2nd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2007)
Operative Vaginal Delivery
Definition and Epidemiology (ACOG Practice Bulletin #17, Operative Vaginal Delivery, Reaffirmed 2012))
- Deliv using forceps or In 2009, 5.5% of vaginal births were operative (National Vital Statistics Report, 2011)
Indications
- Prolonged 2nd stage of labor (see 2nd stage labor arrest, above)
- Suspicion of immediate or potential fetal compromise
- Potential mat intolerance of Valsalva (eg, cardiac dz)
Requirements (All Must Be Met)
- Position of fetal head is known, including Head should be occiput anter or occiput post for forceps, unless operator is skilled w/ rotation.
- Cervix is fully dilated. Station is +2 cm or greater.
- Pelvis is adequate. Bladder is
- Anesthesia is adequate
Contraindications (None Should Be Present)
- <34 w GA for vacuum (elevated risk of IVH)
- Fetal bone demineralization d/o (eg, osteogenesis imperfecta)
- Presence of bleeding d/o (eg, hemophilia, von Willebrand dz) OR mat anticoagulation w/ agent that crosses the placenta (eg, warfarin)
- Unk position of fetal head or head unengaged in pelvis
- Macrosomia is NOT a contraindication; caution for shoulder dystocia is advised, however
Figure 10.5 Placement of vacuum cup on fetal head
|
Optimal placement at “flexion point” |
(Reprinted with permission from Scott JR, Gibbs RS, Karlan BY, et al. Danforth’s Obstetrics and Gynecology. 9th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2003)
Figure 10.6 Correct placement of the forceps blades on the OA fetal head
(Reprinted with permission from Scott JR, Gibbs RS, Karlan BY, et al. Danforth’s Obstetrics and Gynecology. 9th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2003)
Complications of Operative Delivery
- Neonat
Vacuum: Scalp laceration, cephalohematoma (11–16%), subgaleal hematoma (2.6–4.5%), intracranial hemorrhage (0.2%), retinal hemorrhage (up to 75% ® disappear w/i weeks) (BMJ 2004;329:24; Ophthalmology 2001;108:36)
Forceps: Superficial laceration, cephalohematoma (6%), intracranial hemorrhage (0.2%), retinal hemorrhage (0.1–17%) (BMJ 2004;329:24)
- Mat (BMJ 2004;329:24)
Vacuum: Perineal laceration: 3rd degree (9.6%), 4th degree (6.2%) Forceps: Perineal laceration: 3rd degree (12.5%), 4th degree (9.8%)
- Episiotomy may all mat lacerations, but may be necessary for Risk of persistent pelvic floor dysfxn difficult to quantitate. Mat laceration more likely w/ operative deliv, but should be weighed against risks of cesarean. Complications are highest w/ multi instruments (ie, vacuum plus forceps). If 1 fails ® typically proceed w/ cesarean deliv.