The amniotic fluid is the sterile environment hosting the fetus inside the womb during the pregnancy. Ideally, membranes should remain intact until the onset of labor, keeping living conditions optimal and protecting the fetus from infections. Timing of the membrane rupture is the most important factor in the management of pregnancy.
Premature rupture of the membrane is the loss of integrity of the amniotic sac before the labor onset.
Membrane rupture may lead to decreased fluid levels and increased fetal distress.
Interaction with the outside environment increases the infection risk in sterile amniotic environments.
The rupture of membranes is grouped into two main categories based on the timing. If a water break occurs in pregnancies beyond the 37th gestational week, it is referred to as Pre labor Rupture of Membranes (PROM). However, if a water break occurs in the pregnancy before reaching the 37th week, this would be referred to as preterm PROM (PPROM). PROM and PPROM occur in 8% and 3% of pregnancies.
What can cause the membrane to rupture?
Several factors, including environmental and obstetric factors, are associated with membrane rupture.
The most common risk factor for PPROM is genital tract infections. Local infections release inflammatory mediators, causing the weakening of amniotic membranes.
Uterine overdistension observed in multiple gestations and pregnancies with increased fetal weight, and amniotic fluid may cause the membrane rupture. Similarly to the events happening in labor, uterine contractions may physiologically weaken the membranes and result in rupture.
Other major risk factors include a history of the previous PPROM, intraamniotic (the sac containing the "water") infections, shortened cervical length, and vaginal bleeding in late pregnancy.
Women who experienced PPROM in their previous pregnancies carry a three-fold increased risk for membrane rupture. Vaginal bleeding occurring in more than one trimester is associated with a seven-fold increased risk.
Low socioeconomic status, decreased body mass index, and copper and ascorbic acid (Vitamin C) deficiencies could lead to PROM/PPROM. Cigarette smoking (two- to four-fold increased risk) and illicit drug use also contribute to the condition.
How may a mother-to-be identify a membrane rupture?
Classically, membrane rupture presents with a sudden pour or spill of clear or pale yellow fluid from the vagina. However, identifying the water break is not always easy, although the concept sounds self-explanatory. Not all water breaks happen as an abrupt heavy flow.
Women are often unsure if it is a water break, vaginal discharge, or urination. The constant pressure on the bladder already increases the urge for urination, and it is not uncommon that pregnant women may experience uncontrolled urination and wetting undergarments.
Even some minor amniotic water leakage cases might be left unnoticed, assuming that wetting was discharge-related.
How to diagnose the membrane rupture?
The most accurate diagnosis is made by observation of fluid leak from the cervical os or vagina. A gentle push on the top pole of the uterus or coughing may help to visualize the leakage.
A variety of commercially available test kits also could be used for diagnosis. The principle of these tests is based on the detection of certain elements in amniotic fluid. According to recent analyses, the detection of PAMG-1 (AmniSure) diagnoses membrane rupture more sensitively than IGFB-1 (ActimPROM) and nitrazine test.
Normally vaginal secretions have a slightly acidic pH (4.5-6.0), while amniotic fluid has a pH of 7.1-7.3. This difference is used in the home test measuring pH (AmnioSense). Although this test has a high sensitivity in detecting amniotic fluid leakage (98%), it should be remembered that several factors, such as vaginal blood or semen following recent intercourse, may change the vaginal acidic environment reducing the specificity of the test (65%).
Ultrasound is a valuable tool for measuring the amniotic fluid index if a substantial amount of water is lost. However, as minor water leakage will not immediately affect the fluid levels, this method also might be misleading.
What is the management of PROM and PPROM?
The main determinant of the management is gestational age.
Babies who reach the 37th gestational week are considered fully developed and term for delivery. Thus, if a water break diagnosis is confirmed in the early term (37 weeks 0 to 7 days) and term (>38 weeks) periods, delivery should be planned.
Babies in less than 37 weeks of gestation are categorized based on their maturity level; late preterm (34 weeks to 36 weeks 7 days), preterm (24 weeks to 33 weeks 7 days), and before viability (less than 24 weeks).
After birth, the main challenge for premature babies is the use of their lungs. The fetal lung is generally compatible with extrauterine life after the 34th gestational week. Therefore, late preterm pregnancies could be managed as early term and term pregnancies.
Preterm pregnancies require a careful approach, as these fetuses are old enough to be considered viable but young enough to complete lung maturation. A ruptured amniotic sac is no longer protective from external infections. Therefore, antibiotic treatment and close infection control will be required. Moreover, due to the incomplete maturation of fetal lungs, an additional corticosteroid treatment also is indicated to facilitate pulmonary maturation.
As suggested by the name, in the group before 24 weeks, organs essential for extrauterine life are not completely developed. Thus, newborns would not be compatible with life or may have a very limited capacity if birth happened. Therefore, PPROM diagnosis in this group should be followed by family counseling, and labor induction or follow-up with antibiotic treatment should be discussed.
What if membrane rupture is ignored or missed?
Loss of amniotic fluid may lead to decreased amniotic fluid levels (oligohydramnios), which may negatively impact fetal well-being. In up to 60% of cases, chorioamnionitis – infection of the amniotic sac may occur.
If the expectant management is decided, fetal well-being should be monitored with close ultrasound assessments, as these pregnancies carry an increased mortality rate. Reduced amniotic volume may lead to the abruption (separation) of the placenta, presenting with heavy vaginal bleeding.
A significant amount of water loss may cause umbilical cord compression between the uterine wall and fetal parts. If the cervical canal has started to open in addition to the membrane rupture, the umbilical cord may prolapse. In other words, the "swimming" umbilical cord suddenly may "fall out" from the cervical canal with gravitational force. In all these cases, an impaired fetal blood flow will increase fetal distress risk.
Maternal infection parameters, such as fever, inflammation markers, and changes in vaginal discharge color and odor, are also important monitoring parameters.
Signs of fetal distress and chorioamnionitis (intra-amniotic infection) are indications for delivery. It should be noted that, with decreased amniotic fluid, the fetus may face toward the birth canal with the side part of the body, face, breech, or feet.
How can I differentiate the amniotic fluid from the urine or vaginal discharge?
Amniotic fluid is clear or pale yellow in appearance as urine and vaginal secretions. However, unlike amniotic fluid, urine has a specific odor, and vaginal discharge is slightly thicker in consistency.
How could amniotic fluid leakage be tested at home?
Commercially available tests based on pH assessment allow an initial screening of suspected membrane rupture. However, it should be noted that these tests might be affected by blood or semen and have false positive reactions.
I am in my second trimester. Should I be worried about the water leakage even if I am not close to birth and don't have uterine contractions?
Water break is not always associated with labor initiation. It is not uncommon to have membrane rupture without other labor symptoms. However, loss of the integrity of amniotic membranes may lead to loss of amniotic fluid to an endangering extent and might lead to intrauterine infections threatening mothers' and fetuses' lives.
We decided to continue the pregnancy after being diagnosed with membrane rupture. What should I pay attention to during this period?
Fetal well-being should be monitored closely. Mothers-to-be should follow daily fetal movements, which would decrease stress-related conditions. Moreover, infection symptoms, such as fever, and vaginal discharge with odor and color change, might indicate intrauterine infection.