Place of amniocentesis in the assessment of preterm labour

Gastric fluid versus amniotic fluid analysis for the identification of intra-amniotic infection due to Ureaplasma species

OBJECTIVE

Early neonatal sepsis is often due to intra-amniotic infection. The stomach of the neonate contains fluid swallowed before and during delivery. The presence of bacteria as well as neutrophils detected by culture or Gram stain of the gastric fluid during the first day of life is suggestive of exposure to bacteria or inflammation. We undertook this study to determine the relationship between gastric fluid analysis and amniotic fluid obtained by transabdominal amniocentesis in the detection of Ureaplasma species, the most frequent microorganisms responsible for intra-amniotic infection.

MATERIALS AND METHODS

The study population consisted of 100 singleton pregnant women who delivered preterm neonates (<35 weeks) within 7 days of amniocentesis. Gastric fluid of newborns was obtained by nasogastric intubation on the day of birth. Amniotic fluid and gastric fluid were cultured for genital Mycoplasmas, and polymerase chain reaction (PCR) for Ureaplasma species was performed. Intra-amniotic inflammation was defined as an elevated amniotic fluid matrix metalloproteinase-8 concentration (>23 ng/mL).

RESULTS

(1) Ureaplasma species were detected by culture or PCR in 18% (18/100) of amniotic fluid samples and in 5% (5/100) of gastric fluid samples; (2) among the amniotic fluid cases positive for Ureaplasma species, these microorganisms were identified in 27.8% (5/18) of gastric fluid samples; (3) none of the cases negative for Ureaplasma species in the amniotic fluid were found to be positive for these microorganisms in the gastric fluid; (4) patients with amniotic fluid positive for Ureaplasma species but with gastric fluid negative for these microorganisms had a significantly higher rate of intra-amniotic inflammation, acute histologic chorioamnionitis, and neonatal death than those with both amniotic fluid and gastric fluid negative for Ureaplasma species; and (5) no significant differences were observed in the rate of intra-amniotic inflammation, acute histologic chorioamnionitis, and neonatal death between patients with amniotic fluid positive for Ureaplasma species but with gastric fluid negative for these microorganisms and those with both amniotic fluid and gastric fluid positive for Ureaplasma species.

CONCLUSIONS

Gastric fluid analysis has 100% specificity in the identification of intra-amniotic infection with Ureaplasma species. However, the detection of Ureaplasma species by culture or PCR in the gastric fluid of neonates at birth did not identify these microorganisms in two-thirds of cases with microbial invasion of the amniotic cavity. Thus, amniotic fluid analysis is superior to that of gastric fluid in the identification of intra-amniotic infection.

The relationship between amniotic and newborn gastric fluid inflammatory mediators

To determine whether the levels of inflammatory mediators in gastric fluid (GF) of a premature newborn are associated with those in amniotic fluid (AF) of the newborn's mother.

PATIENTS

Twenty-three pairs of pregnant women and their premature newborns <35 weeks gestation, born by Cesarean sections.

METHODS

Amniotic fluids and newborn gastric fluids were obtained from women during Cesarean section procedure. The mother-premature newborn dyads were retrospectively assessed to analyze the clinical and laboratory data. Concentrations of interleukin-6 (IL-6), interleukin-8 (IL-8), tumor necrosis factor-alpha (TNF-α) and mannose-binding lectin (MBL) were compared between amniotic and newborn gastric fluids in each dyad.

RESULTS

Premature newborns and their mothers with funisitis had significantly higher median AF IL-6, TNF-α and GF IL-8 concentrations than those without funisitis (p = 0.022 for AF IL-6; p = 0.023 for AF TNF-α; p = 0.022 for GF IL-8). The concentrations of IL-6, IL-8, TNF-α and MBL in newborn GF were significantly correlated with those in AF in each dyad (p < 0.001, r = 0.872 for IL-6; p < 0.001, r = 0.851 for IL-8; p < 0.001, r = 0.768 for TNF-α; p < 0.001, r = 0.845 for MBL, respectively).

CONCLUSION

The levels of inflammatory mediators in GF of a premature newborn immediately after birth are strongly associated with those in AF of the newborn's mother.

Predictive value of combined cervicovaginal cytokines and gestational age at sampling for intra-amniotic infection in preterm premature rupture of membranes

OBJECTIVE

To determine whether interleukin (IL)-1β, IL-6, and IL-8 in cervicovaginal fluid, alone or in combination with clinical risk factors, could predict intra-amniotic infection in women with preterm premature rupture of membranes (PPROM).

DESIGN

A prospective cohort study.

SETTING

University teaching hospital.

POPULATION

Women with singleton pregnancies presenting PPROM between 20 and 35 weeks of gestation (n = 76).

METHODS

Cervicovaginal fluid samples were collected for IL-1β, IL-6, and IL-8 measurements immediately before amniocentesis. Amniotic fluid obtained by amniocentesis was cultured and the white blood cell count was determined. Clinical risk factors analyzed included demographics and gestational age. Cervicovaginal concentrations of cytokines were measured using a multiplex bead array assay.

MAIN OUTCOME MEASURE

A positive amniotic fluid culture.

RESULTS

The prevalence of a positive amniotic fluid culture was 46.1% (35/76). Stepwise multivariate regression analysis yielded a model using cervicovaginal IL-6 and gestational age at sampling with the area under the curve (AUC) of 0.807 for predicting intra-amniotic infection. The AUC for this model was significantly higher than either parameter retained in this model but no differences were observed between the AUC of this model based on non-invasive variables, and amniotic fluid white blood cell count using invasive amniocentesis for the prediction of intra-amniotic infection.

CONCLUSIONS

Among measured cytokines, the combination of cervicovaginal IL-6 and gestational age appears to be best in predicting intra-amniotic infection and allows for a considerably better accuracy than the use of either factor alone. Overall, this combination performed as well as amniotic fluid WBC count for predicting intra-amniotic infection.

Noninvasive prediction of intra-amniotic infection and/or inflammation in preterm premature rupture of membranes

OBJECTIVE

To develop a model based on noninvasive parameters to predict the probability of intra-amniotic infection and/or inflammation (IAI) in women with preterm premature rupture of membranes (PPROMs).

METHODS

Maternal blood was collected for determination of the C-reactive protein (CRP) level and white blood cell (WBC) count immediately after amniocentesis in 171 consecutive women with PPROMs. Intra-amniotic infection and/or inflammation was defined as a positive amniotic fluid (AF) culture and/or an elevated AF interleukin 6 level (≥2.6 ng/mL).

RESULTS

A risk score based on a model including maternal blood CRP, WBC, parity, and gestational age was calculated for each patient. The model was shown to have an adequate goodness of fit (P = .516), and the area under the receiver-operating characteristic curve was 0.848, indicating very good discrimination.

CONCLUSION

The noninvasive model based on maternal blood CRP, WBC, parity, and gestational age is highly predictive of IAI in women with PPROMs.

Non-invasive prediction of intra-amniotic inflammation in women with preterm labor

OBJECTIVE

To develop a model based on non-invasive variables to predict the probability of intra-amniotic inflammation in women with preterm labor and intact membranes.

METHODS

Transvaginal ultrasonography and digital examination for the assessment of cervical length and cervical dilatation were performed, and maternal blood was collected for the determination of C-reactive protein and white blood cell (WBC) count immediately after amniocentesis in 153 consecutive women with preterm labor. Amniotic fluid obtained by amniocentesis was cultured for aerobic and anaerobic bacteria and mycoplasmas, and the WBC was determined. Intra-amniotic inflammation was defined as an elevated amniotic fluid interleukin-6 concentration (> 2.6 ng/mL). Receiver-operating characteristics (ROC) curves and logistic regression analysis were used for statistical analysis.

RESULTS

The prevalence of a positive amniotic fluid culture was 7.2% (11/153) and the prevalence of intra-amniotic inflammation was 19.6% (30/153). The final logistic regression model was based on non-invasive clinical variables, including gestational age at assessment, cervical length and maternal blood WBC count, which were the best predictors of intra-amniotic inflammation. The model was shown to have an adequate goodness of fit (P = 0.754), and the area under the ROC curve was 0.724, indicating reasonably good discrimination.

CONCLUSION

In women with preterm labor and intact membranes, the risk for intra-amniotic inflammation can be predicted non-invasively with a risk score based on gestational age, cervical length and maternal blood WBC count.

C-reactive protein in vaginal fluid of patients with preterm premature rupture of membranes

OBJECTIVE

To assess whether C-reactive protein (CRP) concentrations in cervical amniotic fluid reflect the condition of the intrauterine environment in patients with preterm premature rupture of membranes (PROM) before 35 weeks of gestation.

METHODS

Amniotic fluid was obtained in 29 consecutive patients admitted with the diagnosis of preterm PROM earlier than 35 weeks of gestation either by amniocentesis or by collecting cervical fluid. CRP was measured in maternal blood, amniotic fluid, vaginal fluid and in cord blood obtained at delivery. Intraamniotic infection was defined as a positive amniotic fluid for aerobic or anaerobic bacteria, or Mycoplasma. The placentas and umbilical cords were examined for the presence of chorioamnionitis and funisitis.

RESULTS

A significant correlation was found between vaginal fluid CRP concentrations and both amniotic fluid (r = 0.95, p < 0.001) and umbilical cord levels (r = 0.47, p < 0.05). No correlation was found between maternal blood and vaginal fluid CRP concentrations. The proportion of patients with intraamniotic infection was 37.9% (11/29). The median (range) vaginal fluid CRP concentration was higher in patients with intraamniotic infection than in those with sterile amniotic fluid [901 (0-1354) vs. 507 (0-798) ng/mL, p < 0.001]. The median (range) vaginal fluid CRP concentration was higher in fetuses with (n = 12) than in those without funisitis (n = 17) [901 (598-1354) vs. 487 (0-1115) ng/mL, p < 0.01]. After adjustment for gestational age, vaginal fluid CRP concentration > 800 ng/mL remained a predictor of intraamniotic infection and funisitis.

CONCLUSIONS

Increased vaginal fluid CRP concentration is associated with intraamniotic infection and funisitis. As CRP is produced by hepatocytes and does not cross the placenta, its measurement in vaginal fluid might be an additional parameter for the assessment of fetal well-being in patients with premature PROM.

Preterm delivery: an overview

Preterm delivery is the leading factor causing neonatal mortality and morbidity. We have conducted a PubMed literature search to obtain an update on the etiology, diagnostic problems and therapeutic considerations of preterm delivery. Approximately 5-10% of all births are premature. Preterm labor is associated with preterm rupture of membranes, cervical incompetence, polyhydramnion, fetal and uterine anomalies, infections, social factors, stress, smoking, heavy work and other risk factors. The diagnosis is made on the patients presenting symptoms, clinical findings and of progressive effacement and dilatation of the cervix. Biochemical markers of preterm delivery are of minor importance in daily clinical work. Measurement of the cervix, however, is a practical and valuable tool to predict preterm delivery. Cervical cerclage can be useful in selected cases. Antibiotics may help to prevent preterm labor in cases of known etiologic agents (e.g. preterm rupture of membranes and urinary infection). The use of tocolytic agents such as beta-sympathetic receptor stimulators can be advocated for a few days. There is evidence that their long-term use is not beneficial and could even be harmful to the fetus. Calcium channel blockers (nifedipine) and a new selective oxytocin receptor antagonist, atosiban, appear to be as effective as beta-sympathomimetic drugs on uterine contractions with fewer side-effects. Prostaglandin synthetase inhibitors such as indomethacin may prevent uterine contractions and can be used prior to the 32nd week of pregnancy. A single course of corticosteroid treatment in two doses of 12 mg betamethasone or 6 mg of dexamethasone is important for the prevention of respiratory distress between the 24th and 34th weeks of pregnancy. Multiple doses may be harmful and should be avoided. In these cases management should depend on gestation age (fetal maturity). Uterine contractions after 34 weeks' gestation are not an indication for tocolytic treatment.