Ketuban Pecah Dini

01Pathophysiology

The fetal membranes consist of two layers: the inner amnion and the outer chorion. These membranes derive their tensile strength primarily from a collagen-rich extracellular matrix, particularly Type I and Type III collagen within the amnion's compact layer. Under normal conditions, the membranes remain intact until active labor, when mechanical forces and localized enzymatic activity cause controlled rupture.

In prelabor rupture of membranes, this process occurs prematurely. The dominant mechanism involves upregulation of matrix metalloproteinases (MMP-1, MMP-2, MMP-9) that degrade collagen fibers, combined with decreased levels of their natural inhibitors (TIMPs, tissue inhibitors of metalloproteinases). This enzymatic imbalance weakens the membrane's structural integrity at focal points, creating a zone of weakness that eventually ruptures under physiological intrauterine pressure.

Infection is the single most important driver in preterm PROM. Ascending bacteria from the vagina and cervix (commonly Ureaplasma urealyticum, Mycoplasma hominis, Gardnerella vaginalis, Group B Streptococcus) colonize the decidua and membranes. This triggers a local inflammatory cascade: neutrophil recruitment, cytokine release (IL-1, IL-6, TNF-alpha), and prostaglandin production. Prostaglandins serve a dual role: they stimulate MMP activity (weakening membranes) and promote myometrial contractions (triggering preterm labor). This explains why chorioamnionitis and preterm labor frequently coexist with PPROM.

Mechanical factors also contribute. Polyhydramnios and multiple gestations cause overdistension of the uterus, applying excessive force on already-compromised membranes. Prior cervical surgery (conization, LEEP) shortens the cervix, reducing the physical barrier between vaginal flora and the membranes. Smoking impairs collagen synthesis and local immune defenses, increasing susceptibility.

The clinical consequence of membrane rupture is loss of the sterile intrauterine barrier. Once ruptured, the amniotic cavity becomes an open system communicating with vaginal flora. This creates a time-dependent risk: the longer the latency period (time from rupture to delivery), the higher the probability of ascending infection leading to chorioamnionitis, funisitis (umbilical cord infection), and neonatal sepsis. Additionally, loss of amniotic fluid reduces the cushioning around the umbilical cord, increasing the risk of cord compression and cord prolapse, particularly if the presenting part is not well-engaged.

02Classification and Clinical Manifestation

By Latency Duration

Signs of Chorioamnionitis

03Diagnostic Workup

The evaluation begins with a sterile speculum examination, which is the best initial test. The examiner inspects the posterior vaginal fornix for visible pooling of clear or slightly cloudy fluid. If pooling is not immediately visible, asking the patient to cough or perform a Valsalva maneuver may provoke a gush of fluid from the cervical os. A fluid sample is then collected for the nitrazine and fern tests.

Nitrazine testing exploits the pH difference between amniotic fluid (pH 7.0 to 7.3) and normal vaginal secretions (pH 4.5 to 6.0). A positive result (blue discoloration) is suggestive but not conclusive, because several contaminants can raise vaginal pH. Blood is the most common culprit for false positives.

Ferning occurs because the sodium chloride content of amniotic fluid crystallizes in an arborization pattern when allowed to air-dry on a glass slide. This test has fewer false positives than nitrazine but can be obscured by heavy blood contamination.

When the clinical picture and bedside tests are equivocal, the AmniSure test is the best next step. This is an immunochromatographic assay that detects placental alpha-microglobulin-1 (PAMG-1), a protein present in high concentrations in amniotic fluid but virtually absent from other vaginal fluids. It is considered the most accurate noninvasive test for membrane rupture.

Ultrasound plays a supportive role. Finding oligohydramnios in a patient with a history consistent with fluid leakage strengthens the clinical suspicion. However, ultrasound cannot confirm or exclude PROM: some patients have significant leakage with normal-appearing fluid volumes, and oligohydramnios has other causes (fetal renal anomalies, uteroplacental insufficiency).

A critical exam principle: never perform a digital cervical examination in a patient with suspected PROM unless delivery is imminent or induction is planned. Digital exams introduce bacteria into the cervical canal and shorten the latency period, substantially increasing infection risk. Cervical dilation and effacement should be assessed visually during the sterile speculum exam or by ultrasound (cervical length measurement).

At the time of the speculum exam, collect a rectovaginal GBS culture (unless a culture result from the current pregnancy within the past 5 weeks is already available) and assess for signs of infection, labor, or cord prolapse.

04Management and Treatment

Term PROM (37 weeks or beyond)

Most women with term PROM enter spontaneous labor within 24 hours. The recommended approach is induction of labor, ideally initiated within 12 to 24 hours of membrane rupture, to minimize infectious morbidity. Oxytocin is the standard induction agent when the cervix is favorable (Bishop score 6 or above). When the cervix is unfavorable, misoprostol (25 mcg vaginally every 4 hours, or 25 to 50 mcg orally every 4 hours) or a Foley catheter balloon can be used for cervical ripening prior to oxytocin. Dinoprostone (PGE2) is another option for ripening.

GBS prophylaxis should be administered intrapartum if the patient is GBS-positive, GBS-unknown, or if rupture has lasted 18 hours or more. The regimen is penicillin G (5 million units IV loading dose, then 2.5 to 3 million units IV every 4 hours until delivery) or ampicillin (2 g IV loading, then 1 g IV every 4 hours). For penicillin-allergic patients, the choice depends on allergy severity: cefazolin for low-risk allergy, clindamycin or vancomycin for high-risk (anaphylaxis-type) allergy, guided by sensitivity testing.

PPROM (24 to 33+6 weeks)

This is where exam questions focus most heavily. The goal is to prolong pregnancy to reduce prematurity while avoiding infection. The core interventions include:

Antenatal corticosteroids are the single most important intervention for fetal benefit. The standard regimen is betamethasone 12 mg IM every 24 hours for 2 doses (or dexamethasone 6 mg IM every 12 hours for 4 doses). Steroids accelerate fetal lung maturity by stimulating surfactant production, and they also reduce the incidence of intraventricular hemorrhage, necrotizing enterocolitis, and neonatal death. A rescue course may be considered if more than 14 days have elapsed since the initial course and delivery is anticipated within 7 days, provided the gestational age is still below 34 weeks.

Latency antibiotics extend the rupture-to-delivery interval and reduce infectious morbidity. The standard regimen is ampicillin 2 g IV every 6 hours for 48 hours, followed by amoxicillin 250 mg orally every 8 hours for 5 days, combined with azithromycin 1 g orally as a single dose (which has replaced the older 7-day erythromycin regimen in current guidelines). This combination provides broad-spectrum coverage against common ascending pathogens and has been shown to prolong latency by approximately 7 days on average.

Tocolysis is controversial. Short-course tocolysis (48 hours) may be considered solely to allow completion of the corticosteroid course, but prolonged tocolysis is not recommended because it may mask signs of infection without improving neonatal outcomes.

Magnesium sulfate for neuroprotection should be administered if delivery is anticipated before 32 weeks of gestation. The regimen is a 4 to 6 g IV loading dose over 20 to 30 minutes, followed by 1 to 2 g/hour maintenance infusion until delivery or for up to 24 hours. This reduces the risk of cerebral palsy in the premature neonate.

Fetal and maternal surveillance during expectant management includes daily fetal heart rate monitoring (nonstress test), periodic biophysical profiles, serial maternal vital signs (watching for fever, tachycardia), and WBC trending if infection is suspected.

Indications for delivery regardless of gestational age include: chorioamnionitis (immediate delivery; antibiotics are started but are not a reason to delay delivery), nonreassuring fetal heart rate tracing, placental abruption, cord prolapse, and reaching 34 weeks of gestation (at which point the risks of continued expectant management generally outweigh the benefits of remaining in utero).

Late Preterm PPROM (34+0 to 36+6 weeks)

Current practice has shifted toward recommending delivery at this gestational age, because the risk of chorioamnionitis during expectant management outweighs the marginal benefit of additional fetal maturation. Betamethasone should be given if not previously administered. GBS prophylaxis is provided as indicated.

Previable PPROM (before 24 weeks)

This carries a poor prognosis. Prolonged oligohydramnios at this gestational age can lead to pulmonary hypoplasia (inadequate lung development due to absent amniotic fluid and thoracic compression), limb deformities from fetal compression, and features of Potter sequence. Survival rates and long-term intact survival are low. Management involves thorough patient counseling about prognosis, with the option of expectant management or pregnancy termination depending on the clinical situation and patient wishes.

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The single most tested concept in PROM questions is the prohibition against digital cervical examination when PROM is suspected but delivery is not yet planned. Students frequently select "perform cervical exam to assess dilation" as a next step, but this is incorrect and harmful because it introduces bacteria and shortens the latency period. The correct next step is always a sterile speculum exam.

A second common trap involves confusing the management of term PROM with preterm PROM. At term, the answer is almost always to proceed with delivery (induction of labor). In contrast, at 24 to 33 weeks, the answer is expectant management with the triad of corticosteroids, latency antibiotics, and GBS prophylaxis. Students who default to "immediate delivery" for a 28-week PPROM without signs of infection will lose the question.

Watch for vignettes that describe a patient with PPROM who then develops fever, uterine tenderness, and fetal tachycardia. This is chorioamnionitis, and the management shifts immediately: deliver regardless of gestational age and start broad-spectrum antibiotics (ampicillin plus gentamicin). A common error is choosing to continue expectant management and "add antibiotics" without proceeding to delivery. Chorioamnionitis is an absolute indication for delivery.

The nitrazine test is a favorite distractor target. Vignettes may describe a patient with vaginal bleeding or recent intercourse alongside suspected PROM. Blood and semen both elevate vaginal pH and cause false-positive nitrazine results. In these cases, the test of choice is AmniSure or reliance on the ferning test, which is not affected by these contaminants.

Finally, remember the magnesium sulfate neuroprotection threshold: it is given when delivery is expected before 32 weeks, not 34 or 37. Questions will test whether you can recall this cutoff precisely. The corticosteroid window (before 34 weeks, with a late preterm course option at 34 to 36+6 in select cases) is a separate threshold, and conflating the two is a common mistake.

The core competency being tested across all PROM questions is the ability to stratify management by gestational age, recognize complications that mandate immediate delivery, and avoid interventions that increase infection risk unnecessarily.