Recognition of meconium staining of the liquor aminii at amnioscopy

Bacteria and endotoxin in meconium-stained amniotic fluid at term: could intra-amniotic infection cause meconium passage?

BACKGROUND

Meconium-stained amniotic fluid (MSAF) is a common occurrence among women in spontaneous labor at term, and has been associated with adverse outcomes in both mother and neonate. MSAF is a risk factor for microbial invasion of the amniotic cavity (MIAC) and preterm birth among women with preterm labor and intact membranes. We now report the frequency of MIAC and the presence of bacterial endotoxin in the amniotic fluid of patients with MSAF at term.

MATERIALS AND METHODS

We conducted a cross-sectional study including women in presumed preterm labor because of uncertain dates who underwent amniocentesis, and were later determined to be at term (n = 108). Patients were allocated into two groups: (1) MSAF (n = 66) and (2) clear amniotic fluid (n = 42). The presence of bacteria was determined by microbiologic techniques, and endotoxin was detected using the Limulus amebocyte lysate (LAL) gel clot assay. Statistical analyses were performed to test for normality and bivariate comparisons.

RESULTS

Bacteria were more frequently present in patients with MSAF compared to those with clear amniotic fluid [19.6% (13/66) versus 4.7% (2/42); p < 0.05]. The microorganisms were Gram-negative rods (n = 7), Ureaplasma urealyticum (n = 4), Gram-positive rods (n = 2) and Mycoplasma hominis (n = 1). The LAL gel clot assay was positive in 46.9% (31/66) of patients with MSAF, and in 4.7% (2/42) of those with clear amniotic fluid (p < 0.001). After heat treatment, the frequency of a positive LAL gel clot assay remained higher in the MSAF group [18.1% (12/66) versus 2.3% (1/42), p < 0.05]. Median amniotic fluid IL-6 concentration (ng/mL) was higher [1.3 (0.7-1.9) versus 0.6 (0.3-1.2), p = 0.04], and median amniotic fluid glucose concentration (mg/dL) was lower [6 (0-8.9) versus 9 (7.4-12.6), p < 0.001] in the MSAF group, than in those with clear amniotic fluid.

CONCLUSION

MSAF at term was associated with an increased incidence of MIAC. The index of suspicion for an infection-related process in postpartum women and their neonates should be increased in the presence of MSAF.

The value of amnioscopy in surveillance of postdate pregnancy

The accuracy and reliability of amnioscopy in detecting the presence of meconium in amniotic fluid and in predicting fetal distress were evaluated in 289 postdate pregnancies. Meconium-stained amniotic fluid tended to be associated with complications of pregnancy such as ABO incompatibility (p less than 0.05), the need for operative delivery (p less than 0.02), and fetal distress at birth (p less than 0.05). Amnioscopy failed to detect the presence of meconium antenatally in most cases (57%), and positive amnioscopy for meconium was unrelated to the incidence of fetal distress. When meconium was present, induction of labour was ineffective in reducing the incidence of fetal distress. Amnioscopy is not recommended for the monitoring of postdate pregnancies.

Management of prolonged pregnancy: results of a prospective randomized trial

Prolonged pregnancy was rigorously defined in 180 gravid women without other complications. Patients were randomly assigned to be serially followed, either by amniocenteses or by oxytocin challenge tests (OCT's). Induction of labor, based upon only (1) a finding of meconium in the amniocentesis group or (2) a positive test in the OCT group, was nearly three times more frequent in the amniocentesis group. The incidence of meconium, which overall was 22% initially and 44% at delivery, as well as the frequencies of obstetric and perinatal complications, were similar in both management groups. Although meconium was significantly associated with abnormal labor progression, intrapartum fetal distress, and low 1 and 5 minute Apgar scores, induction of labor after discovery of meconium, when compared to nonintervention, did not improve perinatal outcome. It is concluded that a search for meconium is of little value in the management of prolonged pregnancy.