PRETERM LABOR

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