4 - preterm delivery

1. Definition of Preterm labor
1. Gestational age 20-37 weeks
2. Contractions with cervical change
2. Epidemiology
1. Incidence 7-8% of deliveries
3. Differential Diagnosis
1. Gastrointestinal
1. Appendicitis
2. Constipation
2. Uterus
1. Uterine Fibroids
2. Placental Abruption
3. Urinary
1. Acute Cystitis
2. Pyelonephritis
3. Nephrolithiasis
4. Musculoskeletal
1. Abdominal wall strain
4. Risk Factors predisposing to Preterm Labor
1. No associated risk factor in 50% of preterm labor
2. Tobacco abuse over 1/2 pack per day Cigarettes
3. Prior cervical cone biopsy
4. Pyelonephritis
5. Advanced cervical dilatation
6. Increased Uterine Size
1. Twin Gestation
2. Polyhydramnios
7. Low pre-pregnant weight (Body Mass Index <19.8)
8. Low socioeconomic status or poor nourishment
9. Prior preterm delivery
10. History spontaneous second trimester abortion
11. African American race
12. Uterine anomaly
1. Unicornuate uterus or bicornuate uterus
2. Uterine Fibroids
3. Diethylstilbestrol (DES) exposure in utero
13. Genitourinary Infection (40% of preterm births)
1. Urinary Tract Infection
1. Pyelonephritis
2. Asymptomatic Bacteriuria in Pregnancy
2. Vaginal infections
1. Group B Streptococcus (PPROM)
2. Bacterial Vaginosis
1. N Engl J Med (1995) 333:1732
3. Sexually Transmitted Disease
1. Neisseria gonorrhoeae
2. Chlamydia trachomatis
3. Trichomonas vaginalis
4. Syphilis
4. Infections with possible risk
1. Ureaplasma urealyticum
2. Mycoplasma hominis
5. Symptoms
1. Keep a high index of suspicion
1. Contraction frequency does not predict risk
2. Symptoms do not predict risk
2. Pelvic pressure
3. Vaginal pain
4. Menstrual-like cramps
5. Backache
6. Vaginal Discharge or fluid leakage (see PPROM)
7. Vaginal Bleeding
6. Signs
1. Examine Cervix as soon as possible
1. Avoid cervical exam until labor if PPROM confirmed
2. Examine Uterus
1. Assess for Abruptio Placentae
2. Check for firm, tender uterus with minimal relaxation
7. Evaluation: Four key concerns
1. Determine if patient is in labor
1. Evaluate abdominal or Pelvic Pain
2. Distinguish preterm labor from preterm contractions
2. Determine if membranes are ruptured
1. See Labs below
3. Establish clear gestational age
1. Review Last Menstrual Period
2. Review Estimated Due Date
3. Review prior ultrasound dating
4. Does fundal height correlate with gestational age
4. Evaluate maternal and fetal health
1. Consider underlying injury or infection
1. Recent trauma
2. Vaginal infection
3. Urinary Tract Infection in pregnancy
2. Consider comorbidity
1. Gestational Diabetes
2. Pregnancy Induced Hypertension
3. Intrauterine Growth restriction
4. Oligohydramnios or Polyhydramnios
3. Evaluate fetal activity and fetal health
1. External fetal monitoring
8. Labs
1. Evaluate for Rupture of Membranes
1. Nitrazine Testing
2. Ferning
2. Microscopy to evaluate Vaginitis
1. Saline wet preparation
2. KOH Preparation
3. Culture
1. Gonorrhea Culture
2. Chlamydia culture
3. Group B Streptococcus Culture (Todd Hewitt media)
1. Periurethral or outer-third of vaginal swab
2. Rectal swab
4. Urine Culture
5. Consider non-genitourinary sources of infection
4. Other Testing
1. Fetal Fibronectin
1. Reassuring if negative
2. Poor Positive Predictive Value
2. Urine testing
1. Urinalysis and Urine Culture
2. Urine drug Screening
5. Fetal Lung Maturity Assessment
1. Indicated for 34 week gestation or greater
9. Radiology: Obstetric Ultrasound
1. Fetal evaluation
1. Biophysical Profile
2. Amniotic fluid index
2. Placental location
3. Fetal Presentation
4. Estimated Fetal Weight (EFW)
5. Ultrasound Exam of Cervical Length
10. Efficacy of evaluation criteria
1. Evaluation criteria do not predict preterm delivery
1. Fetal Fibronectin
2. Uterine contraction frequency
3. Cervical Length assessment
2. These criteria however have Negative Predictive Value
1. No Cervical Length change and negative fibronectin
2. Suggests less than10% chance of preterm delivery
3. References
1. Iams (2002) N Engl J Med 346:250
11. Management
1. See Preterm Labor Management
12. References
1. Iams in Gabbe (2002) Obstetrics p.755