Prelabor rupture of membranes


Prelabor rupture of membranes, previously known as premature rupture of membranes, is breakage of the amniotic sac before the onset of labour. Women usually experience a painless gush or a steady leakage of fluid from the vagina. Complications in the baby may include premature birth, cord compression, and infection. Complications in the mother may include placental abruption and postpartum endometritis.
Risk factors include infection of the amniotic fluid, prior PROM, bleeding in the later parts of pregnancy, smoking, and a mother who is underweight. Diagnosis is suspected based on symptoms and speculum exam and may be supported by testing the vaginal fluid or by ultrasound. If it occurs before 37 weeks it is known as PPROM otherwise it is known as term PROM.
Treatment is based on how far along a woman is in pregnancy and whether complications are present. In those at or near term without any complications, induction of labor is generally recommended. Time may also be provided for labor to begin spontaneously. In those 24 to 34 weeks of gestation without complications corticosteroids and close observation is recommended. A 2017 Cochrane review found waiting generally resulted in better outcomes in those before 37 weeks. Antibiotics may be given for those at risk of Group B streptococcus. Delivery is generally indicated in those with complications, regardless of how far along in pregnancy.
About 8% of term pregnancies are complicated by PROM while about 30% of preterm births are complicated by PROM. Before 24 weeks PROM occurs in fewer than 1% of pregnancies. Prognosis is primarily determined by complications related to prematurity such as necrotizing enterocolitis, intraventricular hemorrhage, and cerebral palsy.

Signs and symptoms

Most women will experience a painless leakage of fluid out of the vagina. They may notice either a distinct "gush" or a steady flow of small amounts of watery fluid in the absence of steady uterine contractions. Loss of fluid may be associated with the baby becoming easier to feel through the belly, decreased uterine size, or meconium seen in the fluid.

Risk factors

The cause of PROM is not clearly understood, but the following are risk factors that increase the chance of it occurring. In many cases, however, no risk factor is identified.

Weak membranes

Fetal membranes likely break because they become weak and fragile. This weakening is a normal process that typically happens at term as the body prepares for labor and delivery. However, this can be a problem when it occurs before 37 weeks. The natural weakening of fetal membranes is thought to be due to one or a combination of the following. In PROM, these processes are activated too early:
Infection and inflammation likely explains why membranes break earlier than they are supposed to. In studies, bacteria have been found in the amniotic fluid from about one-third of cases of PROM. Often, testing of the amniotic fluid is normal, but a subclinical infection or infection of maternal tissues adjacent to the amniotic fluid, may still be a contributing factor. In response to infection, the resultant infection and release of chemicals subsequently weakens the fetal membranes and put them at risk for rupture. PROM is also a risk factor in the development of neonatal infections.

Genetics

Many genes play a role in inflammation and collagen production, therefore inherited genes may play a role in predisposing a person to PROM.

Diagnosis

To confirm if a woman has experienced PROM, a clinician must prove that the fluid leaking from the vagina is amniotic fluid, and that labor has not yet started. To do this, a careful medical history is taken, a gynecological exam is conducted using a sterile speculum, and an ultrasound of the uterus is performed.
  • History: a person with PROM typically recalls a sudden "gush" of fluid loss from the vagina, or steady loss of small amounts of fluid.
  • Sterile speculum exam: a clinician will insert a sterile speculum into the vagina in order to see inside and perform the following evaluations. Digital cervical exams, in which gloved fingers are inserted into the vagina to measure the cervix, are avoided until the women is in active labor to reduce the risk of infection.
  • * Pooling test: Pooling is when a collection of amniotic fluid can be seen in the back of the vagina. Sometimes leakage of fluid from the cervical opening can be seen when the person coughs or performs a valsalva maneuver.
  • * Nitrazine test: A sterile cotton swab is used to collect fluid from the vagina and place it on nitrazine paper. Amniotic fluid is mildly basic compared to normal vaginal secretions which are acidic. Basic fluid, like amniotic fluid, will turn the nitrazine paper from orange to dark blue.
  • * Fern test: A sterile cotton swab is used to collect fluid from the vagina and place it on a microscope slide. After drying, amniotic fluid will form a crystallization pattern called arborization which resembles leaves of a fern plant when viewed under a microscope.
  • * Fibronectin and alpha-fetoprotein blood tests

    Classification

  • Prelabor rupture of membranes : when the fetal membranes rupture early, at least one hour before labor has started.
  • Prolonged PROM: a case of prelabor rupture of membranes in which more than 18 hours has passed between the rupture and the onset of labor.
  • Preterm prelabor rupture of membranes : prelabor rupture of membranes that occurs before 37 weeks gestation.
  • Midtrimester PPROM or pre-viable PPROM: prelabor rupture of membranes that occurs before 24 weeks' gestation. Before this age, the fetus cannot survive outside of the mother's womb.

    Additional tests

The following tests should only be used if the diagnosis is still unclear after the standard tests above.
  • Ultrasound: Ultrasound can measure the amount of fluid still in the uterus surrounding the fetus. If the fluid levels are low, PROM is more likely. This is helpful in cases when the diagnosis is not certain, but is not, by itself, definitive.
  • Immune-chromatological tests are helpful, if negative, to rule out PROM, but are not that helpful if positive since the false-positive rate is relatively high.
  • Indigo carmine dye test: a needle is used to inject indigo carmine dye into the amniotic fluid that remains in the uterus through the abdominal wall. In the case of PROM, blue dye can be seen on a stained tampon or pad after about 15–30 minutes. This method can be used to definitively make a diagnosis, but is rarely done because it is invasive and increases risk of infection. But, can be helpful if the diagnosis is still unclear after the above evaluations have been done.
It is unclear if different methods of assessing the fetus in a woman with PPROM affects outcomes.

False positives

Like amniotic fluid, blood, semen, vaginal secretions in the presence of infection, soap, urine, and cervical mucus also have an alkaline pH and can also turn nitrazine paper blue. Cervical mucus can also make a pattern similar to ferning on a microscope slide, but it is usually patchy and with less branching.

Differential diagnosis

Other conditions that may present similarly to premature rupture of membranes are the following:
  • Urinary incontinence: leakage of small amounts of urine is common in the last part of pregnancy
  • Normal vaginal secretions of pregnancy
  • Increased sweat or moisture around the perineum
  • Increased cervical discharge: this can happen when there is a genital tract infection
  • Semen
  • Douching
  • Vesicovaginal fistula: an abnormal connection between the bladder and the vagina
  • Loss of the mucus plug

    Prevention

Women who have had PROM are more likely to experience it in future pregnancies. There is not enough data to recommend a way to specifically prevent future PROM. However, any woman that has had a history of preterm delivery, because of PROM or not, is recommended to take progesterone supplementation to prevent recurrence.

Management

The management of PROM remains controversial, and depends largely on the gestational age of the fetus and other complicating factors. The risks of quick delivery vs. watchful waiting in each case is carefully considered before deciding on a course of action.
As of 2012, the Royal College of Obstetricians and Gynaecologists advised, based on expert opinion and not clinical evidence, that attempted delivery during maternal instability increases the rates of both fetal death and maternal death, unless the source of instability is an intrauterine infection.
In all women with PROM, the age of the fetus, its position in the uterus, and its well-being should be evaluated. This can be done with ultrasound, Doppler fetal heart rate monitoring, and uterine activity monitoring. This will also show whether or not uterine contractions are happening which may be a sign that labor is starting. Signs and symptoms of infection should be closely monitored, and, if not already done, a group B streptococcus culture should be collected.
At any age, if the fetal well-being appears to be compromised, or if intrauterine infection is suspected, the baby should be delivered quickly by induction of labour.