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5. Prelabor Rupture of Membranes
5.1 Introduction
Prelabor rupture of membranes (PROM) remains a subject of great clinical relevance and a problem encountered by each and every obstetrician in day-to-day practice. Preterm prelabor rupture of membranes (PPROM) is rupture of membranes prior to 37 weeks of gestation, but before the onset of labor. PPROM is far more difficult to manage than PROM at term. Several issues need to be considered in formulating a plan of management. While intra-amniotic infection and its sequelae are the primary maternal risks, prematurity is the principal risk to the fetus which can lead to increased neonatal morbidity and mortality.
5.2 Definition [1, 2]
5.2.1 Prelabor Rupture of Membranes (PROM)
Prelabor rupture of membranes is defined as rupture of membranes before the onset of labor.
5.2.2 Term Prelabor Rupture of Membranes (TPROM)
When the rupture of membranes occurs beyond 37 weeks but before the onset of labor, it is called term prelabor rupture of membranes.
5.2.3 Preterm Prelabor Rupture of Membranes (PPROM)
When the rupture of membranes occurs before 37 completed weeks but before the onset of labor, it is called preterm prelabor rupture of membranes.
5.2.4 Prolonged Rupture of Membranes
Rupture of membranes for >24 h before delivery is called prolonged rupture of membranes.
5.3 Incidence [3–5]
PROM occurs in approximately 10% of all pregnancies, and in 70% of these cases, it occurs in pregnancies at term.
PPROM occurs in 3% of all pregnancies and is responsible for approximately 30% of all preterm deliveries.
5.4 Etiology [5–7]
Subclinical intrauterine infection is a major predisposing factor, especially at early gestation.
Women with PPROM in previous pregnancy are at increased risk for recurrence in next pregnancy.
Prior preterm labor in the current pregnancy.
Low socioeconomic status.
Body mass index ≤19.8.
Nutritional deficiencies.
Smoking.
Sexually transmitted infections (STIs) in female.
Cervical conization in the past.
Uterine distention (e.g., multiple pregnancy, hydramnios).
Cervical cerclage done for cervical incompetence.
Vaginal bleeding during pregnancy.
Presence of a short cervix (< 25 mm by TVS).
Invasive procedures during pregnancy (e.g., amniocentesis, chorionic villi sampling).
Though there are so many of these known risk factors, still none could be identified in most cases of preterm labor.
The underlying pathophysiology in PROM is considered to be collagen degradation in the fetal membranes caused by increased metalloproteinases. Also in pregnancies complicated by PPROM, amnion also exhibits a higher degree of cell death and apoptosis regulated by bacterial endotoxin, interleukin-1, and tumor necrosis factor-α. These all result in a weakened amnion [6].
5.5 Result of PROM [4]
If managed expectantly, half of the women with TPROM deliver within 5 h and 95% within 28 h. Also, whatsoever may be the clinical presentation or obstetric management, delivery occurs within 1 week of rupture of membranes in 50% of cases with PPROM.
5.6 Diagnosis
To decide for gestational age-specific obstetric management.
There is increased possibility of cord prolapse and cord compression if the presenting part is not fixed.
If delivery is delayed after rupture of membranes, intrauterine infection is more likely as time interval increases.
History.
Sterile speculum examination.
Ultrasonography.
5.6.1 History
Patient gives typical history of sudden gush of liquor. At times patient gives history of intermittent leaking, continuous leaking of small amount of fluid, or just a feeling of wetness. Thus detailed history of amount, color, and smell of liquor should be elicited. History of time of rupture of membranes should be taken. History of perception of fetal movements should also be taken.
5.6.2 Sterile Speculum Examination
There will be presence of pool of amniotic fluid in posterior fornix also known as amniorrhexis.
Clear fluid may be seen coming out from cervical canal.
If no fluid is seen, we can ask the patient to cough as this may cause liquor to drain.
By doing per speculum examination, we can also estimate cervical dilatation, exclude cord prolapse, and take cultures [4].
In doubtful cases with a strong history of leaking, patient may be asked to wear a sterile sanitary pad for 30–60 min and observed.
- 1.
Nitrazine test: The pH of vaginal secretions is acidic and normally ranges from 4.5 to 5.5, whereas the amniotic fluid pH is 7.0–7.5. The use of nitrazine indicator is simple and fairly reliable method. The test papers are impregnated with dye and are used to test the vaginal fluid while doing per speculum examination. The color of the reaction between these paper strips and vaginal fluids is seen and interpreted by comparing with a standard color chart. A pH above 6.5 indicates ruptured membranes. The presence of blood, semen, or bacterial vaginosis may give false-positive test. Also false-negative test may be obtained when amniotic fluid is less.
- 2.
Ferning pattern: Microscopic examination of vaginal fluid shows characteristic arborization or ferning. Amniotic fluid when dried on a glass slide crystallizes to form a fern-like pattern due to the presence of sodium chloride, protein, and carbohydrate.
The above two tests have shown the best results with a sensitivity of 90% [8].
- 3.
Lanugo hair: The presence of fetal lanugo hair in vaginal fluid when examined microscopically was considered indisputable evidence of membrane rupture. However, because of limited amounts of fetal lanugo hair in amniotic fluid and also because of the fact that such hairs were present in amniotic fluid only in later weeks of pregnancy, this method never became popular.
- 4.
Cytologic diagnosis: These tests were based on cytologic inspection for fetal squamous cells in the vagina, using various stains including Masson stain, Sudan III stain, Papanicolaou stain, Pinacyanole stain, acridine orange stain, and the most popular Nile blue sulfate stain. Although fetal cell-staining techniques were considered rapid, simple, and durable, concerns about their accuracy emerged. They were also time-consuming, needed trained cytologists, were not effective before 32 weeks of gestation, and did not provide certain diagnosis of membrane rupture.
5.6.3 Ultrasonography
Ultrasonographic evaluation of amniotic fluid volume does help in documenting oligohydramnios, but is not diagnostic for PROM. If after proper evaluation the diagnosis still remains unclear, then we can instill indigo carmine dye (1 mL in 9 mL of sterile normal saline) transabdominally under the guidance of ultrasound. We can then observe the passage of blue fluid into the vagina which can be confirmed by a stained vulval pad [2, 5]. We should not use methylene blue dye for this test because it has been associated with hyperbilirubinemia and hemolytic anemia in infants. Though ultrasonography is not necessary to confirm PROM, it does help in determining the gestational age and position of the fetus, localization of the placenta, residual amniotic fluid volume, estimated fetal weight, and presence of any abnormalities in the fetus [ 10]. A low initial amniotic fluid index has been shown to be associated with shorter latency period and an increased risk of chorioamnionitis. However, amniotic fluid volume assessment does not accurately predict the time of delivery, and thus should not be used alone to decide regarding conservative management.
5.6.4 Newer Biochemical Tests
IGFBP-1 (Actim PROM) test: It is a rapid test that specifically detects insulin-like growth factor-binding protein-1 (IGFBP-1) in the vaginal fluid. It is a simple bedside test and can be used as a complimentary test to confirm the clinical diagnosis of PROM [11, 12].
PAMG-1 (AmniSure®) test: It is a rapid immunoassay test which detects placental alpha-microglobulin-1 (PAMG-1) and is found to be reliable in the diagnosis of PROM. The test has a sensitivity and specificity of 98.9 and 100%, respectively [7, 8, 11, 13].
It is FDA approved.
Simple and easy to perform.
Does not require a speculum examination.
Has no gestational age limitation.
5.6.5 Role of Amniocentesis
Intrauterine infection can be diagnosed by positive amniotic fluid cultures in 36% of women with PPROM. Most infections are subclinical with no obvious signs and symptoms of chorioamnionitis. Current evidence also tells us that infection is a cause of rupture of membranes rather than its result. Although by going for amniocentesis we can detect subclinical infection before clinical picture of chorioamnionitis develops and also before the onset of fetal infection, the evidence at present is not sufficient to recommend amniocentesis for the diagnosis of intrauterine infection [8].
If we want a favorable obstetric outcome, a timely and accurate diagnosis of prelabor rupture of membranes is critical. A false-positive diagnosis of PROM especially preterm PROM may lead to unnecessary obstetric interventions and delivery of a preterm baby thus increasing perinatal morbidity and mortality. Thus every effort should be made to reach at a correct diagnosis.
5.7 Complications
The fetal membranes act as a barrier to ascending infection. Once the membranes rupture, both the mother and fetus are at risk of infection and other complications.
5.7.1 Neonatal Complications [2, 7]
Respiratory distress syndrome (RDS) occurs in 10–40% cases of PPROM and causes 40–70% of neonatal deaths.
Despite initial suggestions, subsequent observations do not support association of accelerated pulmonary maturation with PPROM [14].
Neonatal infections.
Intraventricular hemorrhage (IVH).
Necrotizing enterocolitis (NEC).
Increased risk of neurodevelopmental impairment.
Fetal pulmonary hypoplasia occurs in 26% of PPROM before 22 weeks.
Skeletal deformities.
Severe oligohydramnios may lead to an increased incidence of cord compression and abnormal fetal heart pattern in labor.
Infections and cord accident contribute to 1–2% risk of antenatal fetal demise.
5.7.2 Maternal Complications [4, 7]
Clinically evident intra-amniotic infection occurs in 15–25% and is seen more frequently with prolonged PPROM, severe oligohydramnios, and repeated vaginal examinations.
Postpartum infections occur in 15–20%, with incidence higher at early gestation.
Abruptio placentae in 2–5%.
As more fetuses with PPROM present with malpresentation, thus there is increased risk of cesarean delivery with its attendant complications as compared with term deliveries.
5.8 Management
5.8.1 Confirmation of the Diagnosis of PROM and Its Importance
Early and correct diagnosis of PPROM would allow the obstetrician to plan for management according to gestational age for a better perinatal outcome and minimal complications. On the other hand, a false-positive diagnosis of PPROM may lead to unnecessary obstetric interventions [7].
Confirm gestational age and fetal presentation, and assess fetal well-being by subjecting all patients to electronic fetal monitoring (EFM) during the initial period of observation to assess any abnormality of fetal heart rate (FHR) and uterine activity.
If FHR tracings are abnormal or there is evidence of chorioamnionitis, one should proceed for delivery.
Vaginal bleeding should raise suspicion of placental abruption, and delivery should be considered.
5.9 Gestational Age-Specific Management
5.9.1 Term Prelabor Rupture of Membranes (TPROM)
In these cases delivery should be planned and intrapartum group B streptococcal (GBS) prophylaxis given if indicated [4].
Timing of delivery.
Method of induction.
Role of antibiotics.
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