Labor, Emergency Medicine

Basics

Labor denotes the sequence of physiologic occurrences that result in a fetus being transported from the uterus through the birth canal.

Description

Labor brings about changes in the cervix to allow passage of fetus through birth canal
Synchronous, coordinated contractions of the uterus
Contractions progress in magnitude, duration, and frequency to produce dilation of the cervix and ultimate delivery
Labor is divided into 3 stages:
- Stage 1 (cervical stage): From onset of uterine contractions to full dilation of cervix
- Stage 1 is further divided into latent and active phases:
  - In the latent phase, uterine contraction with little change in cervical dilation or effacement; contractions are mild, short (<45 sec), and irregular
  - This is followed by the active phase, which begins around time of cervical dilation of 3 " 4 cm; contractions are strong, regular (every 2 " 3 min), and last longer (>45 sec)
- Stage 2: From onset of complete cervical dilation to time of delivery of infant
- Stage 3: From time of delivery of baby to time of placental delivery
Total duration of labor varies with each woman
Generally, lengths of 1st and 2nd stages of labor are significantly longer for nulliparous woman:
- Nulliparous: Mean length for 1st stage of labor is 14.4 hr and for 2nd stage of labor is 1 hr
- Parous: Mean length of 1st stage of labor is 7.7 hr and for 2nd stage of labor is 0.2 hr
Length of 2nd stage of labor is greatly influenced by "3 Ps " :
- Passenger (infant size and presentation)
- Passageway (size of bony pelvis and soft tissues)
- Powers (uterine contractions)
Problems with any of these 3 Ps can cause abnormal progression of labor:
- Fetal malposition, uterine dysfunction, cephalopelvic disproportion
False labor (Braxton Hicks contractions):
- Irregular, nonsynchronous contractions of uterus several weeks to days before onset of true labor, and do not cause cervical dilation

Etiology

Premature labor occurs in 8 " 10% of pregnancies.
30 " 40% of premature labor is caused by uterine, cervical, or urinary tract infections
Premature rupture of membranes is defined as rupture of amniotic/chorionic membranes at least 2 hr before onset of labor in patient before 37 wk gestation:
- This occurs in only 3% of pregnancies but accounts for 30 " 40% of all premature births

Diagnosis

Signs and Symptoms

Symptoms of labor:
- Intermittent low abdominal pain with or without low back pain
- Occurring regularly at least every 5 min
- Lasting 30 " 60 sec
Preterm labor is of sufficient frequency and intensity to bring about changes in dilation or effacement of cervix before 37 wk
Labor is not associated with vaginal bleeding:
- Patients with 3rd-trimester abdominal pain or vaginal bleeding should raise suspicion of placenta previa or placental abruption
Sudden release of clear fluid from vagina or feeling of constant perineal wetness can represent rupture of membranes:
- This is not always associated with labor but often leads to onset of labor

History

Gestational age
Prenatal care
Previous pregnancies:
- Complications
- C-section
Recent infections

Physical Exam

Assess fundal height:
- Centimeters from pubic bone to top of uterus
- Correlates with number of weeks after 2nd trimester
- Can help determine gestational age if unknown
Sterile pelvic exam to assess cervical dilation and effacement

Do not perform a pelvic exam if vaginal bleeding is present.

Essential Workup

Patients presenting in possible labor should have immediate sterile pelvic exam to assess dilation, effacement of cervix, and possibility of imminent delivery.
Bimanual pelvic exam should NOT be done in 3rd-trimester patient with vaginal bleeding until US can be done to assess for placenta previa or placental abruption.
Patients with suspected rupture of membranes should have sterile speculum exam with visual exam of cervix and collection of fluid from vaginal area
Suggestive of rupture of membranes:
- Presence of ferning when fluid is allowed to dry on a slide
- Presence of pooling of fluid in vagina
- Change of color of litmus paper from yellow to blue
Patients with preterm labor and cervical changes should have urinalysis with culture and cervical cultures
Fetal monitoring should be initiated

Diagnosis Tests & Interpretation

Lab

If patient is in labor, CBC, type, and screen should be sent.
Urinalysis for proteinuria
In patients with no prenatal care, obtain Rh factor and antibody screen.
Cervical cultures and urine culture in patients with preterm labor

Imaging

Not generally needed
3rd-trimester patients with abdominal pain and vaginal bleeding should have emergent US to evaluate for placenta previa or abruption.

Differential Diagnosis

Braxton Hicks contractions (false labor) are irregular uterine contractions without associated cervical changes:
- Contractions can be every 10 " 20 min
Round uterine ligament pain, musculoskeletal back pain
Other common causes of abdominal pain, such as appendicitis, ovarian cyst, diverticulitis, nephrolithiasis, UTI

Treatment

Pre-Hospital

Emergency medical services personnel should place patients in labor on oxygen and in left lateral recumbent position to maximize delivery of oxygen to uterus
Maternal transport of high-risk obstetric patients before delivery results in improved outcomes instead of transfer of neonate after delivery
Air transport of high-risk obstetric patients has been shown to be beneficial and cost effective
Patients in labor who are transported by aircraft should have high-flow oxygen available in the event of cabin decompression at high altitudes

Initial Stabilization/Therapy

If delivery is imminent (presenting part visible), prepare for immediate vaginal delivery in ED (see "Delivery, uncomplicated " )

Ed Treatment/Procedures

Unless delivery is imminent, patient should be sent directly to the labor and delivery (L&D) unit
If transport to L&D will be delayed, or if transfer to another facility is necessary, these steps should be taken:
- Consider IV antibiotics for unknown group B Streptococcus status
- IV hydration with 1 L NS or 5% dextrose in lactated Ringer over 30 " 60 min
- Maternal monitoring
- Fetal monitoring
- If labor needs to be arrested (premature fetus), begin a tocolytic such as ²-agonist terbutaline or magnesium sulfate:
  - Magnesium toxicity is suggested by loss of deep tendon reflexes
  - High doses of magnesium can cause cardiac dysrhythmias and respiratory depression.

Medication

Magnesium sulfate: 4 " 6 g IV over 30 min, followed by 2 " 6 g/hr
Terbutaline: 0.25 mg SC; may repeat same dose in 30 min

Consider antibiotic prophylaxis for patients with history of cardiac lesions.

Follow-Up

Disposition

Admission Criteria

All patients in labor who are not at risk for imminent delivery should be admitted to L&D
Preterm patients in labor demand immediate obstetric consultation and should be admitted to L&D for further treatment

Discharge Criteria
Patients with false labor may be discharged only after obstetric consultation, confirmation of fetal well-being, and close follow-up is arranged:

False labor may progress to true labor

Pearls and Pitfalls

If vaginal bleeding is present, must rule out placental abruption or previa
Do not perform a digital exam if bleeding is present
Pelvic exam must be sterile in a patient in labor
False labor may progress to true labor

Additional Reading

Berghella V, Baxter JK, Chauhan SP. Evidence-based labor and delivery management. Am J Obstet Gynecol. 2008;199:445 " 454.
DeCherney A, Nathan L, Goodwin TM, et al., eds. Current Diagnosis and Treatment, Obstetrics and Gynecology. 10th ed. New York, NY: McGraw-Hill; 2007.
Liao JB, Buhimschi CS, Norwitz ER. Normal labor: Mechanism and duration. Obstet Gynecol Clin North Am. 2005;32:145 " 164.
Wilson W, Taubert KA, Gewitz M, et al. Prevention of infective endocarditis: Guidelines from the American Heart Association: A guideline from the American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee, Council on Cardiovascular Disease in the Young, and the Council on Clinical Cardiology, Council on Cardiovascular Surgery and Anesthesia, and the Quality of Care and Outcomes Research Interdisciplinary Working Group. Circulation. 2007;116:1736 " 1754.
Wolfson AB, Hendey GW, Ling LJ, et al., eds. Harwood Nuss ' Clinical Practice of Emergency Medicine. 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2010.

Codes

ICD9

V22.0 Supervision of normal first pregnancy
V22.1 Supervision of other normal pregnancy
V23.9 Supervision of unspecified high-risk pregnancy
644.20 Early onset of delivery, unspecified as to episode of care or not applicable
644.21 Early onset of delivery, delivered, with or without mention of antepartum condition

ICD10

Z34.00 Encntr for suprvsn of normal first pregnancy, unsp trimester
Z34.80 Encounter for suprvsn of normal pregnancy, unsp trimester
Z34.90 Encntr for suprvsn of normal pregnancy, unsp, unsp trimester
O60.00 Preterm labor without delivery, unspecified trimester
O09.90 Supervision of high risk pregnancy, unsp, unsp trimester
O60.10X0 Preterm labor w preterm delivery, unsp trimester, unsp

SNOMED

35874009 Normal labor (finding)
424525001 Antenatal care (regime/therapy)
386322007 High risk pregnancy care (regime/therapy)
6383007 Premature labor (finding)

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