Meconium Concentration Research Articles

Amnioinfusion during labor complicated by particulate meconium-stained amniotic fluid decreases neonatal morbidity

OBJECTIVE: Our purpose was to evaluate the efficacy of prophylactic amnioinfusion in decreasing neonatal morbidity associated with labor complicated by particulate meconium-stained amniotic fluid and to assess potential complications of this procedure. STUDY DESIGN: One hundred five laboring pregnant women with particulate (moderate or thick) meconium by subjective clinical analysis were randomly assigned to receive amnioinfusion or to receive standard obstetric care without amnioinfusion. Patients with any antepartum complications, other than the presence of meconium, were excluded from the study. Statistical analyses consisted of the two-tailed and paired Student t tests, Pearson χ 2 test, and Wilcoxon nonparametric test. Significance was set at p < 0.05. RESULTS: The study included 47 patients in the study group and 58 patients in the control group. A significantly greater proportion of study patients demonstrated decreased meconium concentration between rupture of membranes and delivery (46 of 46 vs 15 of 58, p < 0.001). The relative dilution of meconium consistency by objective analysis was significantly different between the study group and the control group (77.1% decrease vs 9.3% increase, p < 0.001). The proportion of neonates with meconium below the vocal cords was reduced in the study group (two of 47 vs 36 of 58, p < 0.001). Umbilical artery pH was increased in the study group neonates (7.29 ± 0.01 vs 7.25 ± 0.009, p < 0.05). The rate of neonatal acidemia was reduced in the study group (4 of 45 vs 12 of 50, p < 0.05). The rate of meconium aspiration syndrome was reduced in the study group (1 of 47 vs 8 of 58, p < 0.05). Maternal and neonatal morbidity rates were similar. CONCLUSION: Prophylactic amnioinfusion should be considered a possible addition to the intrapartum management of patients with particulate meconium-stained amniotic fluid. (AM J OBSTET GYNECOL 1994;170:842-9.)

Cocaethylene in Meconium Specimens

Cocaethylene, a metabolite of cocaine and ethanol, exhibits cardiac and neurobehavioral effects. In order to determine the prevalence of this compound in meconium specimens, samples which gave a positive result for benzoylecgonine using fluorescence polarization immunoassay were analyzed by gas chromatography/mass spectrometry for cocaine, cocaethylene and benzoylecgonine. Deuterated cocaine, cocaethylene and benzoylecgonine were used as internal standards. Gas chromatography/mass spectrometry cutoff concentrations of 5.0 ng/g were utilized for all analytes. Of the 361 specimens which consecutively confirmed positive for cocaine or benzoylecgonine, 114 (31.6%) tested positive for cocaethylene. Further, cocaethylene accumulates in greater concentrations in meconium than urine, and is a useful analyte for identifying fetal alcohol exposure.

Continuous meconium monitoring during labour using an intrauterine probe

The authors have developed a system to monitor meconium continuously during labour, using a flexible intrauterine probe which detects back-scattered light. The system provides a measurement of the meconium concentration of amniotic fluid during labour every 2 min, with a 60% prediction interval of +or-10 g l-1, and a 99% prediction interval of +or-30 g l-1 (clinically 'thick meconium' contains around 100 g l-1). The noise of the measurement is of the order of +or-10 g l-1, and the response to changes in the meconium concentration is from 40 to 120 s, depending on its configuration. The system also provides other obstetric variables such as fetal heart rate and uterine activity measurement, obtained from a fetal monitor. Preliminary clinical results indicate that this system can measure meconium not apparent to the attending staff; the system can detect changes in the meconium concentration of amniotic fluid; the measurements are confirmed by visual observation at delivery; and changes of meconium concentration seem to correlate with known stressful stimuli. The system therefore provides a new tool from which new variables are obtained, which can greatly enhance clinical research into the pathophysiology of meconium passage and aspiration.

A method for continuous monitoring of meconium in the amniotic fluid during labour

In about 10% of pregnancies overall, the fetus discharges meconium (its bowel contents) into the amniotic fluid during labour. In about 10% of cases where meconium is passed, the fetus gasps, inhaling the sticky meconium into the upper respiratory tract. After birth, the meconium blocks the air passages in the lungs, impairing gas exchange — meconium aspiration syndrome (MAS). Up to 20% of infants suffering from MAS die and recently published studies have shown a long-term effect of MAS in causing cough and wheeze. The risk of meconium aspiration is thought to be increased by intrauterine hypoxia. At present, meconium is only noticed at birth or occasionally when amniotic fluid leaks past the presenting part of the fetus. A method has been developed which measures absolute meconium concentration with a 99% prediction interval of ± 30 gl −1; allows monitoring of the rate of appearance of meconium linearly with a nonlinearity of 5%, and differentiates between meconium and blood. The method uses the ratio of the intensity of back-scattered light from the amniotic fluid at 700 and 415 nm, the latter being near the peak of light absorption by meconium and the former a reference value. The ratio is also affected by the presence of blood. However, blood has specific absorption peaks at 540 and 575 nm from which it can be detected (the presence of blood is also a significant abnormality, and is relatively uncommon). The measurement method could easily be integrated into an optical sensor mounted onto an intrauterine probe. The measurement of back-scattered light at 415, 540 and 700 nm would allow continuous monitoring of meconium which could provide valuable information for the study of the pathophysiology of meconium passage in utero during labour and allow preventative measures to be developed.

Thyroxine sulfate is a major thyroid hormone metabolite and a potential intermediate in the monodeiodination pathways in fetal sheep.

T3 and rT3 production rates in the fetus account for roughly only a third of the total T4 production rate; thus, the fate of the majority of T4 produced in the fetus is unknown (the "T4 disposal gap"). We developed sensitive and specific T4 sulfate (T4S) and T3 sulfate (T3S) RIAs to investigate the roles of these compounds in fetal T4 metabolism. T3, T4, T3S, and T4S were determined in a variety of tissue fluid and/or serum samples obtained from fetal, newborn (n = 6), and adult (n = 6) sheep. Four groups of fetal animals, with gestational ages of 94 days (n = 5), 110-111 days (n = 6), 130-131 days (n = 6), and 145 days (n = 6; term = 150 days), were studied. In addition, type I 5'-monodeiodinase (5'-MDI) activity was quantified in liver and kidney tissues. 5'-MDI activities were lower in 94- to 131-day-old fetuses than in fetuses near term or in newborn animals. Mean serum T3 concentrations increased progressively from 94 days (19 ng/dl) to term (371 ng/dl), while mean T3S and T4S serum concentrations were highest at 130 days gestation (237 and 989 ng/dl), decreasing to term. Serum T3S and T4S concentrations decreased further in newborns and adult sheep. T4S and T3S levels in allantoic fluid were significantly higher than those in urine and amniotic fluid in all fetal age groups studied. T4S levels in bile were high from 94-130 days gestation (873-1006 ng/dl), decreasing by 50% at term (529 ng/dl). T4S concentrations in meconium were 46- to 83-fold higher than those in bile from 94 days gestation to term. In contrast, bile T3S levels increased progressively from 94-145 days gestation (191-605 ng/dl), while meconium T3S levels decreased during the same period (33-14 micrograms/100 g). These data demonstrate that 1) sulfated iodothyronines, particularly T4S, are major thyroid hormone metabolites in the fetus; 2) both T4S and T3S are excreted into bile and urine and concentrated in meconium and allantoic fluid; and 3) the high levels of T4S and T3S in serum and other fluids may reflect lower tissue type I 5'-MDI activities. We speculate that T4S and T3S may be further metabolized to other sulfated metabolites and may account in part for the T4 disposal gap in fetal sheep.

Biochemical analysis of meconium in fetuses presumed to have cystic fibrosis

A series of proteins (albumin, transferrin, alpha 1-antitrypsin, alpha-fetoprotein and pancreatic oncofetal antigen) and enzymes (gamma-glutamyltranspeptidase, aminopeptidase M, alkaline phosphatase, alpha-glucosidase and protease) was measured in fetal meconium extracts. There were 19 fetuses thought to have cystic fibrosis (CF), 13 with neural tube defects, three with chromosome abnormalities and 19 normal controls, all with gestational ages between 18 and 21 weeks. With the exception of alpha-fetoprotein, all the proteins and enzymes were significantly elevated in the CF meconium extracts. The most definitive indicator of a CF fetus was the albumin concentration, where the mean level was five times that found in the control groups. However, five of 19 fetuses assumed to have CF had albumin in the normal range. In these cases the meconium protease levels were grossly elevated. Furthermore, in the same five fetuses meconium concentration of pancreatic oncofetal antigen, a protein synthesized in the fetal pancreas, was also greatly raised. We suggest that post-mortem examination of a fetus thought to have CF should include measurement of meconium albumin, protease and pancreatic oncofetal antigen.

Spectrophotometric determination of meconium concentration in amniotic fluid

When a fetus is acutely distressed, for example as a result of strangulation by the umbilical cord, the bowel content, meconium, may be passed into the amniotic fluid. Assessment of meconial contamination of the amniotic fluid is important in the management of late pregnancy. Fresh or increasing meconium content is an indication for urgent delivery. ‘Old’ meconium is usually distinguished from ‘new’ by visual inspection of the stained amniotic fluid; a more objective method could have advantages. We consider the effects of meconium staining of amniotic fluid on the spectrophotometric properties of the liquor. The absorption spectra of meconial amniotic fluids reveal an excess absorption band, centred around 410 nm. Quantification of the band height is proposed and it is shown that the height is linearly related to meconium concentration, with a proportionality factor, or sensitivity, of 0.046 ± 0.009 (mean ± s.d.) optical density (OD) units per g l −1. This sensitivity factor may be used to estimate meconium concentration in samples of amniotic fluid.