PREMATURE RUPTURE OF FETAL MEMBRANES24 January 2022
Premature rupture of fetal membranes refers to the rupture of fetal membrane before the onset of labour after the period of viability. The fluid that comes out of the vaginal sometimes before the onset of labour or during labour is called amniotic fluid or liquor. The fetal membrane consist of two thin layers of materials called the amnion and chorion. They form the amniotic sac. The amniotic sac encloses the baby and the baby’s water called liquor or amniotic fluid. Sometimes the baby’s water break too early when the baby is not mature enough. This condition is called Prelabour rupture of membranes previously known as premature rupture of fetal membranes (PROM). It is the single most common identifiable factor associated with preterm birth.
Preterm premature rupture of membrane refers to PROM before 37weeks of pregnancy. Spontaneous preterm rupture of the membranes is ROM after or with the onset of labour occurring prior to 37 weeks. Prolonged ROM is any ROM that persists for more than 24 hours and prior to the onset of labour.
PREMATURE RUPTURE OF MEMBRANE; HOW IT HAPPENS
How spontaneous membrane rupture occur is not completely understood. The strength and integrity of the fetal membranes is derive from some membrane proteins, including collagens, fibronectin, and laminin.
Matrix metalloproteases (MMPs) are enzymes that decrease membrane strength by increasing collagen degradation. Tissue inhibitors of MMPs bind to MMPs and inhibit MMP-associated breakdown of these membrane proteins thereby, helping to maintain membrane integrity. A variety of pathologic events such as; subclinical or overt infection, inflammation, mechanical stress, bleeding, can disrupt this and other homeostatic processes and initiate a cascade of biochemical changes that culminate in PROM.
Although, the pathway leading to membrane rupture varies depending on the initiating event. This is not always identifiable. It is likely that all pathways lead to a final common pathway ending in membrane rupture.
CAUSES OF PROM
The exact causes of PROM are not known. However, possible causes and risk factors include:
- Increased friability of the membranes
- Decreased tensile strength of the membranes
- Cervical incompetence
- Multiple previous pregnancies
- Infection of the fetal membranes
- Urinary tract infection
- Lower genital tract infection
- Previous PROM
- Previous preterm birth
- Low pre-pregnancy weight or body mass index (BMI< 19 kg/m2)
- Cigarette smoking
- Bleeding during pregnancy from placenta previa or abruptio placenta.
CONFIRMATION AND DIAGNOSIS OF PROM
The diagnosis of PROM is based on characteristic findings on both history and physical examination. From the history, the symptoms of premature rupture of membrane will include; leaking of fluid through the vaginal intermittently or continuously which might trickle down the thigh, or wetness of the vulva or underpant which might be mistaken for urine.
A sterile speculum examination (a metal/plastic instrument inserted in the vaginal to expose the mouth of the womb) by your doctor will demonstrate pooling of amniotic fluid in the posterior vaginal vault. Pooling is the gold standard for diagnosis. If pooling is not observed, manoeuvres to increase the intra-abdominal pressure are undertaking; your doctor will ask you to cough.
Litmus paper can also be used to distinguish liquor from urine; liquor turns a red litmus paper blue. Nitrazine test can also be done where a yellow nitrazine paper is turned blue by liquor however, false positive might exist in the presence of blood, semen, vaginal infections like bacterial vaginosis or trichomoniasis. An ultrasound scan can be performed to assess the liquor volume which might be reduced. Liquor can also be placed on a clean glass slide to dry then visualise under the microscope; this will demonstrate fern-like pattern and this is called fern test. In some instance where PROM is uncertain, some special test strips such as Amnisure and Actim PROM where available can be used to confirm PROM.
COMPLICATION OF PROM
The complication of PPROM can be to the mother and the unborn baby. Complication to the mother include;
- Abruptio placenta (premature separation of the placenta)
- Chorioamnionitis (infection of the chorion and amnion of the fetal membrane)
- Endometritis (infection of the inner lining of the womb)
- Retained placenta
- Postpartum haemorrhage (excessive bleeding after delivery)
Complication to the unborn baby is usually premature birth and it attendant complications such;
- Respiratory distress syndrome
- Anaemia of prematurity
- Hypothermia; low body temperature
- Hypogycemia; low blood sugar
- Apnoea; cessation of breathing
- Intraventricular haemorrhage
- Necrotizing enterocolitis.
TREATMENT OF PROM
The treatment of PROM is based primarily on an individual assessment of the estimated risk for fetal and neonatal complications should conservative management or delivery be pursued. The risks for maternal morbidity is also considered, particularly when PROM occurs before the limit of potential viability which varies across regions. Delivery will be initiated before complications ensue if there is documented fetal lung maturity after PROM at 32 to 33 weeks. In the absence of documented lung maturity or PROM <32weeks, conservative management can be done and patient place on antibiotic and corticosteroid for lung maturity.
PROM: WHAT TO EXPECT
The decision to continue conservative management will be taken daily after examination and review of available laboratory results to rule out infection. Ones the liquor changes colour, start to smell or the mother develops fever and increase heartbeat, conservative treatment will be stop and labour stimulation will begin. This is done to preserve the mother’s future reproductive potential. About 9 in 10 women with PROM will go into spontaneous labour within 24hrs at ≥ 37weeks and about 5 in 10 at <37weeks. About 1 in 10 ruptured membranes will seal and liquor drainage will stop. Liquor drainage before the age of viability referred to as previable PROM is considered an inevitable miscarriage by some experts. They may advise pregnancy termination after weighing the risk to the mother and possible quality of life of the baby when pregnancy is allowed to continue. The liquor is needed for lungs development and also prevent deformity of the limbs. Very few cases might go beyond 3 to 4 weeks after PROM.