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Preterm Labor
Aka: Preterm Labor- Definition of Preterm Labor
- Contractions with Uterine Cervical Length change
- Gestational age 20-37 weeks
- Late preterm: 34 to 37 weeks
- Early preterm: 32 to 34 weeks
- Very Early Preterm: >32 weeks
- Epidemiology
- Incidence 7-8% of deliveries in 2014 (down from >10% in 2007)
- Differential Diagnosis
- Gastrointestinal
- Uterus
- Urinary
- Musculoskeletal
- Abdominal wall strain
- Risk Factors
- No associated risk factor in 50% of Preterm Labor
- Tobacco Abuse over 1/2 pack per day Cigarettes
- Interval between prior pregnancy <18 months
- Prior Cervical Cone Biopsy or LEEP (RR 2)
- Pyelonephritis
- Preterm cervical changes
- Advanced cervical dilatation
- Cervical Length decreased (<2.5 cm at <28 weeks is associated with a RR 6.19)
- Increased Uterine Size
- Multiple Gestation (50% of twin births, 90% of triplets are born before 37 weeks gestation)
- Polyhydramnios
- Low pre-pregnant weight (Body Mass Index <19.8 kg/m2)
- Low socioeconomic status or poor nourishment
- Prior preterm delivery (RR 1.5 to 2)
- History spontaneous second trimester abortion
- Black patients (14.9% preterm delivery vs 8.9% in non-hispanic white patients)
- Chemical Dependency (Cocaine, Heroin)
- Periodontal Disease
- Comorbidity
- Uterine anomaly
- Unicornuate Uterus or bicornuate Uterus
- Uterine Fibroids
- Diethylstilbestrol (DES) exposure in utero
- Genitourinary Infection (40% of preterm births)
- Urinary Tract Infection
- Vaginal infections
- Sexually Transmitted Disease
- Infections with possible risk
- Ureaplasma urealyticum
- Mycoplasma hominis
- References
- 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
- Keep a high index of suspicion
- Signs
- Examine Cervix as soon as possible
- Assess Uterine Cervical Length and dilation
- Avoid cervical exam until labor if PPROM confirmed
- Examine Uterus
- Assess for Abruptio Placentae
- Check for firm, tender Uterus with minimal relaxation
- Examine Cervix as soon as possible
- Evaluation: Five key concerns
- Precautions
- Preterm Labor patients who deliver within 6 days of presentation: <10%
- Assessment goal is to differentiate the patients at high risk of delivery
- Avoid digital vaginal exam UNLESS delivery is imminent (risk of infection)
- Perform sterile speculum exam and cervical Ultrasound instead
- Preterm Labor patients who deliver within 6 days of presentation: <10%
- Is patient preterm (<37 weeks)?
- Review Last Menstrual Period and prior Ultrasounds (especially earliest Ultrasounds)
- Late preterm: 34 to 37 weeks
- Early preterm: 32 to 34 weeks
- Very Early Preterm: >32 weeks
- Determine if patient is in labor
- Evaluate abdominal or Pelvic Pain
- Distinguish Preterm Labor from preterm contractions
- Findings most suggestive of Preterm Labor
- Contractions >6/hour
- Cervical dilatation >3 cm
- Cervical effacement >80%
- Preterm Rupture of Membranes
- Vaginal Bleeding
- Determine Uterine Cervical Length
- Avoid digital cervical exam due to infection risk (unless imminent delivery)
- Sterile speculum exam
- Ultrasound Exam of Uterine Cervical Length
- Determine if membranes are ruptured
- See Premature Rupture of Membranes
- 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 (Placental Abruption may present with Vaginal Bleeding)
- 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
- Consider underlying injury or infection
- Precautions
- Labs
- Evaluate for Rupture of Membranes
- AmniSure ROM Test (Placental alpha microglobulin 1 or PAMG-1 Protein Marker Test)
- Fluid seen pooling from cervical os
- Nitrazine Testing (pH 7.1 to 7.3)
- Ferning (arborization)
- Microscopy to evaluate Vaginitis
- Saline wet preparation (Trichomonas, Bacterial Vaginosis)
- KOH Preparation
- Culture
- Gonorrhea PCR
- Chlamydia PCR
- Group B Streptococcus Culture (Todd Hewitt media)
- Periurethral or outer-third of vaginal swab
- Rectal swab
- Urinalysis and Urine Culture
- Consider non-genitourinary sources of infection
- Other Testing
- Fetal Fibronectin
- Reassuring if negative
- Poor Positive Predictive Value
- Urine testing
- Fetal Fibronectin
- Fetal Lung Maturity Assessment
- Indicated for 34 week gestation or greater
- Evaluate for Rupture of Membranes
- Imaging: Obstetric Ultrasound
- Fetal evaluation
- Biophysical Profile
- Amniotic fluid index
- Placental location
- Fetal Presentation
- Estimated Fetal Weight (EFW)
- Ultrasound Exam of Uterine Cervical Length
- Oligohydramnios (may suggest Rupture of Membranes)
- Fetal evaluation
- Efficacy: 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 (3 cm or more) and negative fibronectin
- Suggests <10% chance of preterm delivery within 14 days
- References
- Evaluation criteria do not predict preterm delivery
- Evaluation
- Universal Cervical Length screening is not currently part of guidelines and is controversial
- Management
- Prevention
- Progesterone Therapy
- Indications
- Single gestation pregnancy (not useful in Multiple Gestation pregancies) AND
- Prior spontaneous preterm delivery OR Cervical Length <=2 cm before 24 weeks gestation
- Protocol: Prior spontaneous preterm delivery
- Hydroxyprogesterone caproate (Makena) 250 mg IM weekly from 16 to 24 weeks OR
- Protocol: Cervical Length <=2 cm before 25 weeks gestation
- Vaginal micronized Progesterone 200 mcg daily
- References
- Indications
- Cervical Cerclage
- Indicated in Prior spontaneous preterm delivery AND Cervical Length <=2.5 cm before 24 weeks gestation
- Contraindicated in Multiple Gestation pregnancy (associated with increased preterm delivery risk)
- Owen (2009) Am J Obstet Gynecol 201(4): 375 [PubMed]
- Cervical Pessary (experimental)
- Associated with significantly decreased risk of preterm delivery
- Goya (2012) Lancet 379(9828): 1800-6 [PubMed]
- Progesterone Therapy
- References
- Iams in Gabbe (2002) Obstetrics p.755
- Rundell (2017) Am Fam Physician 95(6): 366-72 [PubMed]