**8. Prelabor rupture of the membranes (PROM)**

Prelabor rupture of membranes (PROM) is defined as `spontaneous leakage of AF prior to onset of labor´ with a gestational age of 37 weeks or more (WHO definition). Preterm PROM (PPROM) is ruptured membranes before 37 weeks of gestation. PROM is a relatively common event in obstetric practice, and the prevalence is reported to be 5-19% of all pregnancies (Hannah et al. 1996).

#### **8.1 Clinical management of PROM**

The management of PROM has been considered controversy since the 1950's. The modern era of this field began in 1966 with several reports that showed increased risk for both the mother and the fetus, when expectant management of PROM was undertaken. PROM without immediate onset of labor was considered to carry a high potential risk of incurring intrauterine infection (Shubeck et al. 1966; Webb 1967).

In the 1950's the perinatal mortality associated with PROM was estimated to range from 2.6% to 11%, and increased with the duration between PROM and delivery. The maternal mortality related to PROM, was reported to be 0.2‰. On the basis that PROM without immediate onset of labor was considered dangerous an aggressive approach to PROM was

Recently a study was published where the association between a high concentration of lactate in amniotic fluid as a possible marker of uterine tissue hypoxia during delivery, pathologic cardiotocography trace (CTG), and adverse neonatal outcome at delivery was shown (Wiberg-Itzel et.al 2011). A sample of AF was collected just before delivery and the lactate concentration was analyzed blinded. An association between high lactate value in amniotic fluid just before delivery and adverse neonatal outcome at birth was confirmed. In the group with AF lactate concentrations greater than 10.1 mmol/L at the last sampling occasion before delivery, significantly more neonates had an adverse neonatal outcome at birth, resuscitation was performed more frequently, and a higher number of newborns were admitted to the neonatal intensive care unit. Two neonates with hypoxic–ischemic encephalopathy grade 2 were found, and both belonged to the group with a high concentration of lactate in amniotic fluid, whereas there were no newborns in the group with lower amniotic fluid lactate that developed hypoxic–

In summary, it was found that the use of CTG together with an analysis of the lactate concentration in AF could be a promising and useful predictor of fetal outcome in labor. The method is easy, non-invasive, and safe for the mother and her unborn child. The findings have important clinical implications in view of the fact that children are still born with an unexpected

Currently, a large collaborative prospective project between 10 European and one African clinic is running. In the "Dysfunctional labor study" data, saliva and amniotic fluid from 5000 primiparas and their deliveries is collected. This in a desire to gain more knowledge about the state called dystocia. The study is scheduled to continue until summer 2012.

Prelabor rupture of membranes (PROM) is defined as `spontaneous leakage of AF prior to onset of labor´ with a gestational age of 37 weeks or more (WHO definition). Preterm PROM (PPROM) is ruptured membranes before 37 weeks of gestation. PROM is a relatively common event in obstetric practice, and the prevalence is reported to be 5-19% of all

The management of PROM has been considered controversy since the 1950's. The modern era of this field began in 1966 with several reports that showed increased risk for both the mother and the fetus, when expectant management of PROM was undertaken. PROM without immediate onset of labor was considered to carry a high potential risk of incurring

In the 1950's the perinatal mortality associated with PROM was estimated to range from 2.6% to 11%, and increased with the duration between PROM and delivery. The maternal mortality related to PROM, was reported to be 0.2‰. On the basis that PROM without immediate onset of labor was considered dangerous an aggressive approach to PROM was

adverse neonatal outcome, even with what is considered to be careful fetal surveillance

**8. Prelabor rupture of the membranes (PROM)** 

intrauterine infection (Shubeck et al. 1966; Webb 1967).

ischemic encephalopathy.

**7.1 Ongoing study** 

pregnancies (Hannah et al. 1996).

**8.1 Clinical management of PROM** 

advised in the 1970's and 1980's. Early induction and operative intervention were suggested, especially if labor had not started within 24 hours. One problem with this aggressive approach was failed inductions with concomitant increased frequency of caesarean sections.

Studies of women with PROM and unfavourable cervix status have been published (Kappy et al. 1979). A spontaneous onset of labor within 24 hours in 85% of the women with established PROM is presented. They also reported a reduced caesarean section rate with expectant management, and no evidence of increased neonatal infections.

In a large randomised trial of 5041 women with PROM they were randomly assigned to immediate induction of labor or expectant management (Hannah et al. 1996). The women were randomised to induction with oxytocin, vaginal PGE2-gel or expectant management up to four days after PROM. If labor had not started within four days, the women were induced with oxytocin or PGE2 gel. The primary outcomes were neonatal infection and women's evaluation of their treatment. They found no significant differences between the study groups, and concluded that in both management groups a similar rate of neonatal infections (2-3%) and caesarean sections (10%) were found. Women evaluated early induction of labor more positively than expectant management.

A Swedish PROM study was conducted in the 1990's where 1385 women were included (Ladfors et al. 1996). The result showed a 13% prevalence of PROM after 34 weeks of gestation. They compared obstetric and neonatal outcome between two different expectant management groups, expectancy for 48 or 72 hours. The result showed a higher rate of spontaneous deliveries among nulliparas in the `late´ induction group compared with `early´ induction. The rate of instrumental delivery was lower in the `late´ induction group, but the rate of caesarean sections was similar. They concluded that expectant for 72 hours was to be recommended. Digital vaginal examination before onset of labor was not allowed in this trial. Low frequencies of maternal and fetal infections were found, and there were no differences between the groups.

False negative diagnosis with visual inspection at speculum examination was found to be 12%. No disadvantage, i.e. infections, was found for mother or child if the woman was sent home after a false negative speculum examination. They questioned the value of using biochemical tests in the management of women with suspected PROM. No comments were made on the assumed false positive diagnosis in women with suspect PROM. All women included in the trial had visible AF at examination, but 3.1% of them had intact membranes at delivery. AF

#### **8.2 Historical review of PROM tests**

In 1920's, it was found that vaginal pH turned from acid to neutral or alkaline when contaminated with amniotic fluid. In 1938 the nitrazine test was introduced, which measured pH in vaginal secrete within a narrower range. This method has been widely used all over the world.

The crystallisation pattern of AF was first described in 1950's. The crystallisation phenomenon, also called ferning or arborisation test is dependent on the relative concentration of electrolytes, proteins and hydrocarbonates in AF. The crystallisation test is nowadays still one of the most commonly used methods in clinical practice worldwide.

Lactate Level in Amniotic Fluid, a New Diagnostic Tool 235

Fibronectin is a large plasma glycoprotein. Three sub-types are available, of which one is feta derived. The concentration of fetal fibronectin in amniotic fluid is 5-10 times higher than in maternal plasma. In the 1990's many papers were published about fetal fibronectin and its usefulness to detect AF in women with suspect PROM. To use fetal fibronectin when detecting PROM is a sensitive test (97%) but a test with a very low specificity (27%). Additionally, in patients without rupture of the membranes, the interval between sampling and delivery was shown to be significantly shorter if fetal fibronectin was present. The conclusion was that the presence of fetal fibronectin in cervicovaginal secretions may be a good marker for impending labor rather than a good test for ruptured membranes. Today fetal Fibronectin is used in a combination with ultrasound, to detect the risk of premature

Insulin-like growth factor (IGF) is a peptide and is bound to a binding protein (IGFBP) in the blood circulation. IGFBP-1 is a placental protein and is present in much higher concentrations in AF as compared with serum, cervical mucous, urine or seminal plasma. A commercial kit, with monoclonal antibodies to IGFBP-1 attached to a small wand has been available since 1993 (actim PROM-test™). During the last decade, many papers have been published on the actim PROM-Test™. The sensitivity of the test is reported to be 71-100% and specificity 88-100%. It has been concluded that actim PROM-test™ is one of the most accurate diagnostic tests today in the diagnosis of suspected PROM. However, contamination of maternal blood or leakage of IGFBP-1 through stretched fetal membranes may cause false positive tests. A false negative result may occur if there is an inadequate sampling, intraamniotic infection, vaginal discharge, maternal blood loss, or prolonged time from rupture of membranes to application of the test. Gestatational age should not influence

B-HCG is a glycoprotein produced exclusively by syncytiotrophoblasts in the placenta. Several studies have investigated β-HCG as a useful test for the diagnosis of PROM in the third trimester. These studies have shown a sensitivity of 68-100% and a specificity of 95-97%.

In 1975, the placental alpha microglobulin–1 (PAMG-1) protein was isolated from AF. Antibodies were obtained against the protein and Amnisure® is an immunochemical method, used to measure the content of PAMG-1 protein in vaginal fluid, in cases with suspect PROM. Amnisure® has been available on the market since 2005. In a study which included 203 women with suspected PROM, a sensitivity of 98.8% and a specificity of 100% were found.

Lac-test, a good, reliable and useful clinical test for PROM with both a high sensitivity and a high specificity has been presented in several publications. The test is easy to use in the clinical situation with an answer immediately available at the bedside. A vaginal fluid lactate concentration of >4.5 mmol/l in women having a history of suspect PROM is shown

**9. Lactate in AF, a new diagnostic tool when handling a suspect PROM** 

**Insulin-like growth factor binding protein-1 (PROM-test™)** 

**Fetal fibronectin (ROM-check)** 

delivery.

the test.

**Amnisure®** 

**B-HCG in vaginal washing fluid** 

Fig. 4. Photo taken at microscopy (x 40) of AF from one woman included in the "lac-test" study.

Nile blue sulphate staining of the neutral lipid in cells from fetal sebaceous glands was described in 1960's. The cells turn orange as a consequence of the oxazone in Nile blue. The cells are single or grouped in clusters. Other cells, like vaginal squamous, and pus cells or erythrocytes stain blue. A limitation of this test is that these fat-containing cells are only present after 32 weeks of gestation.

In selecting a spectrum of tests to be used in doubtful instances of ruptured membranes, it was determined that a combination of these three tests described above would produce an accuracy of diagnosis approximating 93%.
