Prelabor Rupture of Membranes

Prelabor rupture of membranes (PROM), previously known as premature rupture of membranes, refers to the rupture of the amniotic sac before the onset of labor. Prelabor rupture of membranes may occur in term or preterm pregnancies. The presentation includes a painless discharge of clear or pale-yellow fluid from the vagina in the form of a large gush or as small, intermittent trickles. Management depends on gestational age. Beyond 34 weeks, the recommendation is to induce labor and, if indicated, use antibiotics for group B streptococcus (GBS) prophylaxis. Prior to 34 weeks, management involves prolonging the pregnancy as long as possible while avoiding intra-amniotic infection (IAI), also known as chorioamnionitis, and minimizing risk to the fetus. The primary complications associated with PROM are related to infections and preterm birth.

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Overview

Definition

Prelabor rupture of membranes (PROM) is defined as the rupture of fetal membranes (the fused chorion and amnion) before the onset of labor (regular uterine contractions causing cervical change).

Epidemiology

Prelabor rupture of membranes complicates approximately 2%–3% of pregnancies.

Risk factors:

  • Genital tract infections (e.g., bacterial vaginosis)
  • PROM or preterm delivery in previous pregnancies
  • Uterine distension:
    • Polyhydramnios 
    • Multiple gestation
  • Cervical incompetence
  • Trauma
  • Cigarette smoking
Table: Epidemiology of PROM
Pre-viable PROMPreterm PROM (PPROM)Term PROM
Gestational age< 24 weeks24–36 weeks> 37 weeks
Frequency< 1% of pregnancies
  • ~ 3% of pregnancies overall
  • ~ 30% of preterm pregnancies
~ 8% of pregnancies
PROM: prelabor rupture of membranes

Pathophysiology and Clinical Presentation

Anatomy

The fetal membranes create the amniotic sac to surround the fetus and protect it from infection. 

  • Composed of 2 layers: 
    • Amnion: 
      • Innermost layer
      • Contains amniotic fluid and fetus
    • Chorion: 
      • Separates amnion from maternal decidua (innermost uterine layer)
      • Acts as a protective barrier
  • Early in pregnancy: 2 distinct layers with the chorionic cavity between
  • Later in pregnancy: Layers fuse to become a single amniochorion.
  • Amniotic fluid:
    • Produced primarily from fetal urine
    • Allows for:
      • Fetal movement → skeletal development
      • Fetal breathing → lung development
The fetal membranes development

Fetal membranes at 7 weeks and 4 months of development:
The membranes arise from trophoblastic and mesodermal tissue. Early in pregnancy, the chorion and amnion are 2 distinct layers with a cavity between. As the pregnancy progresses, the 2 layers fuse to form a single amniochorion in direct contact with the maternal decidua.

Image by Lecturio.

Pathophysiology

  • Poorly understood
  • Membrane strength comes from: 
    • Collagen
    • Fibronectin
    • Laminin
  • Possible mechanism for PROM is the imbalance between matrix metalloprotease (MMP) and MMP inhibitors:
    • MMP degrades collagen.
    • MMP inhibitors maintain membrane integrity.
  • Potential pathologic events may disrupt membranes:
    • Infection
    • Inflammation
    • Mechanical stress
    • Bleeding

Clinical presentation

  • Sudden gush of fluid without labor contractions
  • Often copious, but also small amounts
  • Continuous or intermittent leakage
  • Color of fluid may be:
    • Clear 
    • Straw colored
    • Greenish (meconium stained)
    • Blood tinged (concern for associated placental abruption)
    • Purulent (infected)

Diagnosis

Once labor is excluded, a sterile speculum exam and ultrasound should be performed to diagnose PROM.

  • Pooling
    • Visualize the cervix on sterile speculum exam and ask the mother to bear down (Valsalva maneuver).
    • Positive test: visualization of fluid coming from the cervix (often significant)
    • Most accurate diagnostic test
  • Nitrazine test
    • Collect sample of vaginal fluid on sterile speculum exam.
    • Positive test: pH paper turns blue in presence of basic amniotic fluid.
    • Low positive predictive value → also turns blue in presence of: 
      • Semen
      • Bacterial vaginosis
      • Blood
  • Ferning
    • Obtain swab of vaginal fluid → allow to dry on a glass slide
    • Positive result: Ferning pattern appears on a slide and is visible on microscopy.
    • Cervical mucus can leave a similar ferning pattern (false positive).
  • Ultrasound: 
    • Suggestive of PROM: oligohydramnios (maximal vertical pocket of fluid < 2 cm) 
    • Relatively low sensitivity and specificity:
      • PROM often exists without oligohydramnios.
      • Oligohydramnios often exists without PROM.
  • Exclude labor:
    • Assess contractions on tocometry.
    • Assess cervical dilation visually on sterile speculum exam (try to avoid digital exam which ↑ risk of intra-amniotic infection (IAI)).
CTG in a case of prelabor rupture of membranes

Intrapartum fetal monitoring with tocometry:
The bottom panel shows tocometry (records uterine contractions). The upper panel shows the fetal heart rate (baseline of around 140/min) with moderate variability and late heart rate decelerations (descent time > 60 sec with nadir after the peak of the contraction, and slow return up to baseline of 140). The tracing is from a case of fetal cord prolapse through the cervix (a potential complication of PROM), which compromises fetal blood flow. The fetal heart rate pattern is nonreassuring.

Image: “CTG in a case of prelabor rupture of membranes” by Department of Obstetrics and Gynaecology, Royal United Hospital Bath NHS Trust, Bath, UK. License: CC BY 2.0

Management

Management is based on gestational age, group B streptococcus (GBS) status, signs of labor or contractions, and signs of IAI.

General management

  • Confirm fetal well-being:
    • Non-stress test (fetal monitoring with tocometry)
    • Assess amniotic fluid levels with ultrasound.
  • Deliver if:
    • > 34 weeks gestational age
    • IAI is present (regardless of gestational age).
  • Monitor for development of IAI; ↑ risk in PROM, ↑↑↑ risk in preterm prelabor rupture of membranes (PPROM):
    • Fever
    • Maternal leukocytosis > 15,000/L
    • Maternal tachycardia
    • Fetal tachycardia > 160/min for ≥ 10 minutes
    • Purulent amniotic fluid on exam
    • Fundal tenderness
    • Contractions/labor
  • Antibiotics for group B streptococcus (GBS):
    • IV penicillin or ampicillin in labor
    • If preterm and/or GBS status is unknown → collect a swab at presentation
    • Treat in labor if:
      • GBS positive
      • GBS unknown with risk factors
    • Risk factors for fetal GBS disease:
      • Preterm (< 37 weeks gestation)
      • Rupture of membranes (ROM) ≥ 18 hours
      • Fever ≥ 100.4°F (≥ 38°C)
      • Prior documented GBS colonization in urine
      • Prior infant with early-onset GBS disease

Management of PROM by gestational age

Fetal age > 34 weeks:

  • Induction of labor
  • Antibiotics: 
    • For GBS prophylaxis only
    • Given if patient is:
      • GBS positive 
      • Unknown with risk factors 
      • Gestational age of 34–37 weeks (risk factor)

Fetal age 24–33 weeks:

  • Antibiotics:
    • Latency antibiotics: 
      • Attempt to ↑ time to delivery by preventing IAI
      • Regimen: azithromycin + ampicillin/amoxicillin
    • GBS prophylaxis: Treat when delivery is imminent and GBS is positive or unknown.
  • Corticosteroids:
    • Betamethasone
    • Benefits:
      • ↑ Fetal lung maturity
      • ↓ Intraventricular hemorrhage (IVH)
      • ↓ Necrotizing enterocolitis
  • Magnesium sulfate: for fetal neuroprotection against cerebral palsy
  • Tocolytics: 
    • Given only for initial 48 hours (allows time for maximum benefit of steroids)
    • Prevents contractions if not yet started
    • Do not give if contractions are already present → likely due to infection → ↑ risk of morbidity
  • Delivery indications:
    • Achieve 34 weeks of gestation
    • IAI
    • Spontaneous labor
    • Fetal distress

Fetal age < 24 weeks:

  • Expectant management or induction of labor
  • No antibiotics, corticosteroids, tocolysis, or magnesium sulfate
  • ↑↑ Risk of infection if pregnancy continues

Complications

Neonatal complications

Complications can be related to:

  • Infection:
    • Fetal infection
    • Sepsis
    • Neurodevelopmental impairment
  • Compromised blood flow:
    • Umbilical cord compression and/or prolapse
    • Placental abruption:
      • Occurs with rapid decompression of uterus
      • Obstetric emergency 
  • Oligohydramnios (with early PPROM):
    • Pulmonary hypoplasia
    • Orthopedic and facial abnormalities
  • Preterm delivery:
    • Respiratory distress syndrome (most common)
    • IVH
    • Necrotizing enterocolitis
    • Retinopathy of prematurity
    • Cerebral palsy
    • Patent ductus arteriosus

Maternal complications

  • Infections:
    • IAI/chorioamnionitis
    • Postpartum endometritis
    • Sepsis
  • Postpartum hemorrhage (common after IAI)
  • Deep vein thrombosis (due to prolonged bed rest in PPROM)

Differential Diagnosis

  • Urinary incontinence: an involuntary loss of urine. Urinary incontinence is common towards the end of pregnancy due to increased pressure on the bladder from the fetus. Prelabor rupture of membranes (PROM) should always be ruled out 1st (pooling, nitrazine test, ferning, and ultrasound). Urinalysis should also be obtained to rule out urinary tract infection (UTI), which can increase the risk of urinary incontinence. Management in pregnancy is usually reassurance and observation since incontinence is typically minor.
  • Urinary tract infection: an infection of the urinary system most commonly caused by Enterobacteriaceae, especially Escherichia coli. Presentation typically includes suprapubic pain, dysuria, and urinary urgency. Diagnosis is made with urinalysis and culture. Pyelonephritis is more common in pregnancy and is diagnosed when flank pain and fever accompany the UTI. Management is with antibiotics.
  • Vaginal infection/vaginitis: inflammation of the vagina can resulting in discharge, itching, and discomfort. The most common causes include bacterial vaginosis (BV), candidiasis, and trichomoniasis. Sexually transmitted infections can also cause cervicitis with purulent discharge. Discharge from vaginitis (especially BV) can be confused with amniotic fluid. Diagnosis is made on microscopy with KOH and wet prep of vaginal discharge. Management is with antimicrobials.
  • Semen: If the patient presents to labor and delivery complaining of PROM, ask directly about recent sexual activity. Semen will cause nitrazine paper to turn blue (false positive), and sperm can be seen on microscopy. If PROM is confidently ruled out and history or exam suggest recent unprotected intercourse, the gush of fluid is commonly semen.

References

  1. Scorza, W. E. (2020). Management of prelabor rupture of the fetal membranes at term. In Barss, V. A. (Ed.), UpToDate. Retrieved February 22, 2021, from https://www.uptodate.com/contents/management-of-prelabor-rupture-of-the-fetal-membranes-at-term
  2. Duff, P. (2020). Preterm prelabor rupture of membranes: Clinical manifestations and diagnosis. In Barss, V. A. (Ed.), UpToDate. Retrieved February 22, 2021, from https://www.uptodate.com/contents/preterm-prelabor-rupture-of-membranes-clinical-manifestations-and-diagnosis
  3. Duff, P. (2020). Preterm prelabor rupture of membranes: Management and outcomes. In Barss, V. A. (Ed.), UpToDate. Retrieved February 24, 2021, from https://www.uptodate.com/contents/preterm-prelabor-rupture-of-membranes-management-and-outcome 
  4. Baker, C. J. (2020). Neonatal group B streptococcal disease: Prevention. In Barss, V. A. (Ed.), UpToDate. Retrieved February 24, 2021, from https://www.uptodate.com/contents/neonatal-group-b-streptococcal-disease-prevention
  5. American College of Obstetrics and Gynecology (2020). Practice Bulletin No. 217: Prelabor rupture of membranes. Retrieved February 22, 2021, from https://www.acog.org/clinical/clinical-guidance/practice-bulletin/articles/2020/03/prelabor-rupture-of-membranes 
  6. Cunningham, F. G., Leveno, K. J., et al. (2010). Williams Obstetrics (23rd ed. pp. 50‒54).
  7. Dayal, S. (2020). Premature rupture of membranes. In Hong, P. (Ed.) StatPearls. Retrieved February 24, 2021, from https://www.statpearls.com/articlelibrary/viewarticle/27659/

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