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Breakage of the amniotic sac before the onset of labour From Wikipedia, the free encyclopedia
Prelabor rupture of membranes (PROM), previously known as premature rupture of membranes, is breakage of the amniotic sac before the onset of labour.[2] Women usually experience a painless gush or a steady leakage of fluid from the vagina.[1] Complications in the baby may include premature birth, cord compression, and infection.[2][1] Complications in the mother may include placental abruption and postpartum endometritis.[2]
| Prelabor rupture of membranes | |
|---|---|
| Other names | Premature rupture of membranes |
| |
| Positive fern test with amniotic fluid as seen under the microscope | |
| Specialty | Obstetrics |
| Symptoms | Painless gush or a steady leakage of fluid from the vagina[1] |
| Complications | Baby: Premature birth, cord compression, infection[2][1] Mother: Placental abruption, postpartum endometritis[2] |
| Types | Term, preterm[2] |
| Risk factors | Infection of the amniotic fluid, prior PROM, bleeding in the later parts of pregnancy, smoking, a mother who is underweight[2] |
| Diagnostic method | Suspected based on symptoms and examination, supported by testing the fluid or ultrasound[2] |
| Differential diagnosis | Urinary incontinence, bacterial vaginosis[3] |
| Treatment | Based on how far along a woman is in pregnancy and whether complications are present[2] |
| Frequency | ~8% of term pregnancies,[2] ~30% of preterm pregnancies[4] |
Risk factors include infection of the amniotic fluid, prior PROM, bleeding in the later parts of pregnancy, smoking, and a mother who is underweight.[2] Diagnosis is suspected based on symptoms and speculum exam and may be supported by testing the vaginal fluid or by ultrasound.[2] If it occurs before 37 weeks it is known as PPROM (preterm prelabor rupture of membranes) otherwise it is known as term PROM.[2]
Treatment is based on how far along a woman is in pregnancy and whether complications are present.[2] In those at or near term without any complications, induction of labor is generally recommended.[2] Time may also be provided for labor to begin spontaneously.[1][2] In those 24 to 34 weeks of gestation without complications corticosteroids and close observation is recommended.[2] A 2017 Cochrane review found waiting generally resulted in better outcomes in those before 37 weeks.[5] Antibiotics may be given for those at risk of Group B streptococcus.[2] Delivery is generally indicated in those with complications, regardless of how far along in pregnancy.[2]
About 8% of term pregnancies are complicated by PROM while about 30% of preterm births are complicated by PROM.[2][4][6] Before 24 weeks PROM occurs in fewer than 1% of pregnancies.[2] Prognosis is primarily determined by complications related to prematurity such as necrotizing enterocolitis, intraventricular hemorrhage, and cerebral palsy.[2][7]
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.[8] Loss of fluid may be associated with the baby becoming easier to feel through the belly (due to the loss of the surrounding fluid), decreased uterine size, or meconium (fetal stool) seen in the fluid.[9]
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.[10]
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 (preterm). 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:[12]
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 (too small to detect) 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 (cytokines) subsequently weakens the fetal membranes and put them at risk for rupture.[10] PROM is also a risk factor in the development of neonatal infections.[13]
Many genes play a role in inflammation and collagen production, therefore inherited genes may play a role in predisposing a person to PROM.[10]
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.[9]
The following tests should only be used if the diagnosis is still unclear after the standard tests above.
It is unclear if different methods of assessing the fetus in a woman with PPROM affects outcomes.[16]
Like amniotic fluid, blood, semen, vaginal secretions in the presence of infection,[9] soap,[10] urine, and cervical mucus[8] also have an alkaline pH and can also turn nitrazine paper blue.[9] Cervical mucus can also make a pattern similar to ferning on a microscope slide, but it is usually patchy[9] and with less branching.[8]
Other conditions that may present similarly to premature rupture of membranes are the following:[8]
Women who have had PROM are more likely to experience it in future pregnancies.[11] 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.[11][9]
| Summary[11] | Fetal age | Management |
|---|---|---|
| Term | > 37 weeks |
|
| Late pre-term | 34–36 weeks |
|
| Preterm | 24–33 weeks |
|
|
Pre-viable |
< 24 weeks |
|
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 (induction of labor) vs. watchful waiting in each case is carefully considered before deciding on a course of action.[11]
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.[17]
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 (GBS) culture should be collected.[18]
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.[11][14]
Both expectant management (watchful waiting) and an induction of labor (artificially stimulating labor) are considered in this case. 90% of women start labor on their own within 24 hours, and therefore it is reasonable to wait for 12–24 hours as long as there is no risk of infection.[14] However, if labor does not begin soon after the PROM, an induction of labor is recommended because it reduces rates of infections, decreases the chances that the baby will require a stay in the neonatal intensive care unit (NICU), and does not increase the rate of caesarean sections.[11] If a woman strongly does not want to be induced, watchful waiting is an acceptable option as long as there is no sign of infection, the fetus is not in distress, and she is aware and accepts the risks of PPROM.[11] There is not enough data to show that the use of prophylactic antibiotics (to prevent infection) is beneficial for mothers or babies at or near term because of the potential side effects and development of antibiotic resistance.[19]
When the fetus is 34 to 37 weeks gestation, the risk of being born prematurely must be weighed against the risk of PROM. Previously it was recommended that delivery be carried out as if the baby was term.[11][8] A 2017 Cochrane review however found waiting resulted in better outcomes when pregnancy is before 37 weeks.[5]
Before 34 weeks, the fetus is at a much higher risk of the complications of prematurity. Therefore, as long as the fetus is doing well, and there are no signs of infection or placental abruption, watchful waiting (expectant management) is recommended.[11] The younger the fetus, the longer it takes for labor to start on its own,[9] but most women will deliver within a week.[10] Waiting usually requires a woman to stay in the hospital so that health care providers can watch her carefully for infection, placental abruption, umbilical cord compression, or any other fetal emergency that would require quick delivery by induction of labor.[11]
In 2017, a review of watchful waiting vs the early birth strategy was conducted to ascertain which was associated with a lower overall risk. Focusing on the 24–37-week range, the review analysed twelve randomised controlled trials from the "Cochrane Pregnancy and Childbirth's Trials Register", concluding that "In women with PPROM before 37 weeks' gestation with no contraindications to continuing the pregnancy, a policy of expectant management with careful monitoring was associated with better outcomes for the mother and baby."[5]
There is believed to be a correlation between volume of amniotic fluid retained and neonatal outcomes before 26 weeks' gestation.[10] Amniotic fluid levels are an important consideration when debating expectant management vs clinical intervention, as low levels, or oligohydramnios, can result in lung and limb abnormalities.[10] Additionally, labor and infection are less likely to occur when there are sufficient levels of amniotic fluid remaining in the uterus.[8] Serial amnioinfusion in pregnancies with PPROM-related oligohydramnios at less than 26 weeks gestation, successfully alleviates oligohydramnios, with perinatal outcomes that are significantly better than the outcome in those with the persistent condition and is comparable with gestations with PPROM in which oligohydramnios never develops.[20]
Before 24 weeks, a fetus is not viable meaning it cannot live outside the mother. In this case, either watchful waiting at home or an induction of labor done.[11]
Because the risk of infection is so high, the mother should check her temperature often and return to the hospital if she develops any signs or symptoms of infection, labor, or vaginal bleeding. These women are typically admitted to the hospital once their fetus reaches 24 weeks and then managed the same as women with PPROM before 34 weeks (discussed above). When possible, these deliveries should take place in a hospital that has expertise in the management of the potential maternal and neonatal complications, and has the necessary infrastructure in place to support the care of these patients (i.e. neonatal intensive care unit).[27] Antenatal corticosteroids, latency antibiotics, magnesium sulfate, and tocolytic medications are not recommended until the fetus reaches viability (24 weeks).[11] In cases of pre-viable PPROM, chance of survival of the fetus is between 15 and 50%, and the risk of chorioamnionitis is about 30%.[9]
Chorioamnionitis is a bacterial infection of the fetal membranes, which can be life-threatening to both mother and fetus. Women with PROM at any age are at high risk of infection because the membranes are open and allow bacteria to enter. Women are checked often (usually every 4 hours) for signs of infection: fever (more than 38 °C or 100.5 °F), uterine pain, maternal tachycardia, fetal tachycardia, or foul-smelling amniotic fluid.[10] Elevated white blood cells are not a good way to predict infection because they are normally high in labor.[9] If infection is suspected, artificial induction of labor is started at any gestational age and broad antibiotics are given. Caesarean section should not be automatically done in cases of infection, and should only be reserved for the usual fetal emergencies.[9]
The consequences of PROM depend on the gestational age of the fetus.[8] When PROM occurs at term (after 36 weeks), it is typically followed soon thereafter by the start of labor and delivery. About half of women will give birth within 5 hours, and 95% will give birth within 28 hours without any intervention.[11] The younger the baby, the longer the latency period (time between membrane rupture and start of labor). Rarely, in cases of preterm PROM, amniotic fluid will stop leaking and the amniotic fluid volume will return to normal.[11]
If PROM occurs before 37 weeks, it is called preterm prelabor rupture of membranes (PPROM), and the baby and mother are at greater risk of complications. PPROM causes one-third of all preterm births.[22] PROM provides a path for disease-causing organisms to enter the womb and puts both the mother and baby at risk for infection. Low levels of fluid around the baby also increase the risk of umbilical cord compression and can interfere with lung and body formation of the baby in early pregnancy.[22]
At any gestational age, an opening in the fetal membranes provides a route for bacteria to enter the womb. This can lead to chorioamnionitis (an infection of the fetal membranes and amniotic fluid) which can be life-threatening to both the mother and fetus.[8] The risk of infection increases the longer the membranes remain open and baby undelivered.[11] Women with preterm PROM will develop an intra-amniotic infection 15–25% of the time, and the chances of infection increase at earlier gestational ages.[11]
PROM occurring before 37 weeks (PPROM) is one of the leading causes of preterm birth. Thirty to 35% of all preterm births are caused by PPROM.[10] This puts the fetus at risk for the many complications associated with prematurity such as respiratory distress, brain bleeds, infection, necrotizing enterocolitis (death of the fetal bowels), brain injury, muscle dysfunction, and death.[8] Prematurity from any cause leads to 75% of perinatal mortality and about 50% of all long-term morbidity.[28] PROM is responsible for 20% of all fetal deaths between 24 and 34 weeks' gestation.[10]
Before 24 weeks the fetus is still developing its organs, and the amniotic fluid is important for protecting the fetus against infection, physical impact, and for preventing the umbilical cord from becoming compressed. It also allows for fetal movement and breathing that is necessary for the development of the lungs, chest, and bones.[8] Low levels of amniotic fluid due to mid-trimester or previable PPROM (before 24 weeks) can result in fetal deformity (e.g. Potter-like facies), limb contractures, pulmonary hypoplasia (underdeveloped lungs),[11] infection (especially if the mother is colonized by group B streptococcus or bacterial vaginosis), prolapsed umbilical cord or compression, and placental abruption.[9]
Most cases of PROM occur spontaneously, but the risk of PROM in women undergoing a second trimester amniocentesis for prenatal diagnosis of genetic disorders is 1%. Although no studies are known to account for all cases of PROM that stem from amniocentesis. This case, the chances of the membranes healing on their own and the amniotic fluid returning to normal levels is much higher than spontaneous PROM. Compared to spontaneous PROM, about 70% of women will have normal amniotic fluid levels within one month, and about 90% of babies will survive.[11]
Of term pregnancies (more than 37 weeks) about 8% are complicated by PROM,[10] 20% of these become prolonged PROM.[9] About 30% of all preterm deliveries (before 37 weeks) are complicated by PPROM, and rupture of membranes before viability (before 24 weeks) occurs in less than 1% of all pregnancies.[11] Since there are significantly fewer preterm deliveries than term deliveries, the number of PPROM cases make up only about 5% of all cases of PROM.[9]
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