Preterm Premature Rupture of Membranes

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The term premature rupture of membranes (PROM) refers to rupture of the fetal membranes (what commonly is called your “water breaking”) prior to the onset of uterine contractions. But today, we’re going to focus specifically on preterm premature rupture of membranes (PPROM), which is any PROM that occurs prior to a gestational age of 37 weeks.

PPROM occurs in roughly 3 percent of pregnancies and accounts for about 33 percent of preterm births. Most of these cases involve viable fetuses, meaning those at 24-37 weeks gestation. In contrast, pre-viable PPROM (PROM before 24 weeks gestation) occurs in less than 1 percent of pregnancies.

Both term PROM and PPROM feature amniotic fluid leaking out through the vagina before your labor contractions have begun. While women with term PROM can simply be admitted to the delivery room and have labor induced (if the membrane rupture does not trigger the labor on its own), or can be delivered through a cesarean section, PPROM can be more problematic. This is because the fetus may not be entirely ready to begin life outside the womb. The level of prematurity makes all the difference. Late PPROM –PROM occurring at 34-37 weeks gestation—requires a course of action that differs from what is required for PPROM occurring at 24-24 weeks, or from PPROM occurring at ages below 24 weeks. In other words, timing is everything.

Generally, PPROM can be diagnosed based on your history and physical exam, and some simple laboratory testing that is done on samples taken from your vagina or cervix. Usually, there is a large gush, or a steady leak, of clear vaginal fluid from the vagina. Doctors will then perform what’s called a Nitrazine test. If this reveals a high pH (your vagina is alkaline instead of being acidic), this indicates that amniotic fluid has leaked from within the womb. The Nitrazine test can be falsely negative, however, if you have experienced prolonged PPROM, meaning that the gush of fluid (the water break) occurred many hours ago. In such cases, the Nitrazine test can be falsely positive, because the vaginal pH will have returned to normal after all of that time. Another test performed is called the fern test, which can support the diagnosis of PPROM based on the appearance of the cervical mucous under the microscope. This test is most sensitive and specific in women who are already in labor.

The fetal fibronectin test is highly sensitive, but is not so specific for PROM. This makes the test useful in ruling out PROM. That’s because, if it comes out negative, doctors can be very sure that your membranes are intact, though if it comes out positive it only might mean that something is wrong. Other tests for vaginal contents include the AmniSure test and the ROM Plus. Doctors also may use ultrasonography to measure the volume of amniotic fluid in your womb. If the amount of fluid is very low, this supports a diagnosis of PPROM.

PPROM can lead to infection of the amniotic fluid and membrane around the fetus and also placental abruption, separation of the placenta from the uterine wall. This, in turn, can lead to infection throughout your body (sepsis). It also can lead to inflammation of the uterine wall after birth (postpartum endometritis). Additionally, PPROM makes cesarean delivery much more likely.

In the event of a placental abruption, the fetus is at extreme risk, since it means that circulation is cut off to fetal tissues, which can lead to fetal death. Similarly, intra-amniotic infection is a major danger to the fetus as well as the mother. It can lead to fetal sepsis and fetal demise. The fetus also is in danger of having underdeveloped lungs, respiratory distress syndrome, hemorrhage in the brain, skeletal deformities, problems with the umbilical cord, slowed neurological developmental or impairment, and neonatal death.

As for treatment of PPROM, if the fetus is at 34 weeks gestation, or older, doctors will induce labor immediately by giving you the hormone oxytocin. This is safe for the soon-to-be born fetus and it works to stimulate fetal contractions. It is not given if a cesarean section is needed, in which case doctors need to do the opposite, namely to prevent or stop uterine contractions. Antibiotics must be given to treat intra-amniotic infection in order to prevent all of the grave consequences mentioned above that can arise for the mother and fetus.

David Warmflash
Dr. David Warmflash is a science communicator and physician with a research background in astrobiology and space medicine. He has completed research fellowships at NASA Johnson Space Center, the University of Pennsylvania, and Brandeis University. Since 2002, he has been collaborating with The Planetary Society on experiments helping us to understand the effects of deep space radiation on life forms, and since 2011 has worked nearly full time in medical writing and science journalism. His focus area includes the emergence of new biotechnologies and their impact on biomedicine, public health, and society.

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