Prelabor Rupture of Membranes

Motunrayo Mobolaji-Lawal

Karen J. Jubanyik

OVERVIEW

Background

Prelabor rupture of membranes (PROM) is the spontaneous rupture of fetal membranes before the onset of labor at any gestational age. Formerly referred to as “premature rupture of membranes,” the new term was agreed upon by the American College of Obstetrics and Gynecology (ACOG) and numerous other professional organizations under the reVITALize efforts to develop standardized data definitions in the field of obstetrics and gynecology. Preterm prelabor rupture of membranes (PPROM) is the spontaneous rupture of fetal membranes before the onset of labor prior to 37 weeks’ gestation. When the duration of time between PROM and the onset of labor is greater than 24 hours, it is referred to as prolonged PROM. PROM at any gestational age is an important cause of maternal and perinatal morbidity and perinatal mortality. Thus, emergency medicine practitioners should be well versed in the early recognition and initial management of PROM and PPROM in order to improve maternal and perinatal outcomes.

Epidemiology

In the United States, the incidence of PROM at term, preterm, and before viability is approximately 8% to 10%, 2% to 4%, and less than 1%, respectively.¹^,² PPROM is the most common cause of preterm birth and is a significant cause of perinatal death. Approximately 18% to 20% of perinatal deaths are attributed to PPROM.²

Risk Factors

The strongest risk factor for the development of PPROM is a history of PPROM or preterm labor in a previous pregnancy; other risk factors are listed in Table 19.1.¹^,³^,⁴^,⁵ In addition, procedures such as cerclage and amniocentesis have been associated with PPROM.⁶ It should be noted that although these have been identified as risk factors that predispose patients to PPROM, most cases of PPROM occur without the presence of any identifiable risk factors.¹

TABLE 19.1 Risk Factors Associated With PPROM^*

Prior History of PPROM	Low Body Mass Index <19.8 kg/m²
Intra-amniotic infection	Poor nutrition, anemia
Placental abruption	Maternal illicit drug use, tobacco use
Short cervical length (25 mm)	Short interval (<12 mo) between pregnancies
Vaginal bleeding in second or third trimester	Oligohydramnios or polyhydramnios
Low socioeconomic status	Multiple gestation
Chronic maternal steroid use	Direct abdominal trauma
Uterine abnormalities (uterine septum)	Collagen vascular disorders (Ehlers-Danlos syndrome, systemic lupus erythematosus)
^*PPROM, preterm prelabor rupture of membranes.
Data from American College of Obstetrics and Gynecology. Prelabor rupture of membranes: ACOG practice bulletin no. 188. Obstet Gynecol. 2018;131(1):e1-e14; Waters TP, Mercer B. Preterm PROM: prediction, prevention, principles. Clin Obstet Gynecol. 2011;54(2):307-312; Verbruggen SW, Oyen ML, Phillips ATM, Nowlan NC. Function and failure of the fetal membrane: modelling the mechanics of the chorion and amnion. PLoS One. 2017;12(3):e0171588; and Waters TP, Mercer BM. The management of preterm premature rupture of the membranes near the limit of fetal viability. Am J Obstet Gynecol. 2009;201(3):230-240.*

PATHOGENESIS

The fetal membrane consists of an outer thick cellular membrane called the chorion and an inner thin collagenous membrane with high tensile strength called the amnion (Figure 19.1).⁴ The chorion acts as an immunologic barrier, whereas the amnion acts as a structural barrier.⁴ This bilayer structure surrounds the fetus and plays a crucial role in protecting and physiologically maintaining the fetus throughout the pregnancy.⁷ The pathogenesis of PROM at a molecular and cellular level is multifaceted. It is thought to occur as a result of an increase in local mediators (cytokines, prostaglandins, and protein hormones) and a decrease in amniotic collagen content and function.⁸ This ultimately results in decreased tensile strength of the fetal membrane.

CLINICAL FEATURES

History

Patients presenting with PROM typically report an abrupt gush of fluid from the vagina, slow constant leakage of fluid from the vagina, or a sensation of perineal wetness.⁹ A detailed but focused history should be obtained including gravidity and parity, estimated gestational age, presence of contractions, presence of vaginal bleeding, history of sexually transmitted diseases or vulvovaginitis, pregnancy course including any maternal or fetal complications, signs or symptoms of infection, and recent sexual intercourse.

Physical Examination

It is recommended that the gynecologic examination of a patient suspected of having PROM be carried out with care so as not to introduce infection into the uterine cavity.¹⁰ A sterile speculum examination should be performed. In the presence of PROM, a sterile speculum examination will reveal the flow of amniotic fluid from the cervical os and the accumulation of amniotic fluid in the posterior vaginal fornix.¹ If passage of fluid from the cervical os is not immediately observed, the patient may be asked to perform a Valsalva maneuver such as coughing or fundal pressure may be applied in order to facilitate extrusion of fluid from the uterus if present.⁶ During the sterile speculum examination, the cervix should be assessed for dilatation and effacement as well as signs of inflammation or infection.¹ Cervical and vaginal swabs for Chlamydia and Neisseria gonorrhoeae
should be obtained during the sterile speculum examination if there is suspicion for infection. Perineal culture for Group B streptococcus (GBS) testing should also be performed if the GBS status is unknown. A digital cervical examination is not recommended and should be avoided as it can increase the risk of introducing infection and shortens the latency period.¹ In addition, a digital cervical examination rarely provides additional information to that provided by a sterile speculum examination.¹⁰

Figure 19.1: The placenta and fetal membranes. A, The placenta and amniotic sac, B, A full-term placenta, C, The placenta. (From McConnell TH, Hull KL, eds. The reproductive system. In: Human Form, Human Function: Essentials of Anatomy & Physiology. Philadelphia, PA: Lippincott Williams & Wilkins; 2010:698).

Natural History of Pregnancies Complicated by Prelabor Rupture of Membranes

Latency period refers to the interval of time between the rupture of membranes and the onset of labor.¹¹ The longer the latency period, the higher the risk of developing chorioamnionitis.¹² Various factors affect the length of the latency period. The length of the latency period is inversely related to the gestational age at the time of rupture of membranes.¹¹ In the absence of obstetric interventions, half of the patients who experience PROM at term will have spontaneous onset of labor within 12 hours and 95% will have onset of labor within 72 hours.² Conversely, of the patients who experience PPROM, 50% will go into labor within 24 to 48 hours and 70% to 90% will go into labor within 7 days.² The length of the latency period is also inversely related to the severity of oligohydramnios.² In addition, the presence of excessive myometrial thinning (<12 mm), cervical dilatation greater than 1 cm on presentation, nulliparity, twin pregnancy, fetal growth restriction, intra-amniotic infection, placental abruption, and nonreassuring fetal heart tones are all independently associated with a shorter latency period.²^,¹¹^,¹²

DIFFERENTIAL DIAGNOSIS

The differential diagnosis for PROM includes, but is not limited to, any process that can cause loss of genitourinary fluid during pregnancy. This includes vaginal discharge that could be physiologic or infectious, urinary leakage resulting from urinary incontinence, vaginal bleeding, a cervical mucus plug that signifies cervical effacement and dilatation, or excessive perspiration.²^,¹³

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