Throughout a normal pregnancy, the fetus is enclosed in a growing sac of watery fluid called the amniotic fluid, from the name of the sac which secretes it, the amniotic sac. The water protects the fetus from trauma as well as from infection.
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This water often escapes at the onset of labor or afterwards, and this is called ‘breaking of waters’ or in medical terms, the rupture of the membranes. Rupture of membranes may occur before the onset of labor in term pregnancies in 10% of women.
Labor usually ensues within 24 hours of membrane rupture in half of these women. In those cases where the rupture is premature, this may not happen. In approximately 30% of women with rupture of membranes at term, as well, labor is delayed for over 48 hours. The healthcare provider may then induce labor because the risk of uterine and fetal infection increases with the duration of ruptured membranes.
A common confusion is whether the fluid escaping is urine or indeed amniotic fluid. If there is any doubt, it is always wise and indeed, mandatory to go to the hospital even if the expected delivery date is far away. A simple test will identify the source of the fluid and thereby unnecessary management can be avoided.
Management of Ruptured Membranes
The first step is to verify that the membranes have indeed ruptured. This is possible by:
- Clinical examination: using a vaginal speculum to establish that clear fluid is leaking from the cervical os, as well as ruling out cord prolapse
- Laboratory tests: nitrazine tests using nitrazine-treated swabs to confirm that the fluid is alkaline
- Immunoassay swabs: these are immunochromatographic strips based on the detection of IGFBP-1 or PAMG-1, and are both more accurate and faster than nitrazine strips, which results in better diagnosis.
- Ultrasound testing: this mode of examination is extremely helpful in establishing fetal size, presentation, and amniotic fluid volume which can contribute to the diagnosis.
The mother should be assessed to rule out intrauterine infection and to evaluate fetal presentation and lie. A cardiotocography (monitoring the fetal heart rate) is useful in helping to establish fetal wellbeing.
There are certain tests for vaginal infection with a group of organisms called group B streptococci (GBS). These should be ruled out as they contribute to the risk of membrane rupture and uterine infection, as well as neonatal infection (most often causing pneumonia, sepsis or meningitis).
If all the tests indicate that there is no active infection, and no other obvious risk factors, expectant management may be proceeded with provided the woman agrees. In some other cases, active management is indicated, including antibiotic prophylaxis where required and the induction of labor.
Preterm Premature Rupture of Membranes
Preterm premature rupture of membranes (PPROM) is another complication which occurs before the pregnancy reaches term. It is found in about 2-4% of pregnancies, but is the etiological factor in up to 40% of preterm labors which are not induced for medical reasons. About a fifth of perinatal deaths occur in this subset of infants.
The risks to the fetus include fetal death, fetal respiratory distress syndrome, as well as intestinal complications of prematurity. The lack of adequate amniotic fluid due to PPROM at early gestational ages can lead to severe complications such as adhesions between various parts of the body.
There is also a higher incidence of cesarean section in this group. However, over 95% of women who are near term and develop PPROM do go into labor within 28 hours, while before 26 weeks, only just over 50% go into labor within a week.
Management of PPROM
Management involves confirming the escape of amniotic fluid without a digital vaginal examination, with low vaginal and rectal swabs to pick up GBS infection. The pregnancy can be significantly prolonged with appropriate antibiotic prophylaxis, fetal monitoring, and maternal monitoring with CRP and ultrasonography.
In any case, hospitalization is mandatory. Tocolysis (i.e. using drugs to delay birth) is not usually indicated, but may be used in very early PPROM to allow corticosteroid administration to accelerate lung maturity, if the conditions for their use are met. These include the lack of clinical infection and antepartum hemorrhage.
Pregnancy prolongation is not a significant objective after 34 weeks, and the main focus is on achieving delivery without sepsis, through expectant or active management after 37 completed weeks of gestation, or expectant management between 34 and 37 weeks.
Before 34 weeks, prematurity is the main danger, thus conservative management is the primary option if infection is ruled out. Bed rest and corticosteroids are often recommended to help the fetus achieve as much maturity as possible.
Vaginal delivery is chosen in the absence of specific indications for a cesarean section or if both mother and fetus appear to be normal. Such births should happen preferably in a centre which offers neonatal intensive care and a preterm unit.
Reviewed by: Dr Tomislav Meštrović, MD, PhD