Mechanism(s) of in utero meconium passage

Department of Obstetrics and Gynecology, Harbor-UCLA Medical Center, Torrance, CA 90502, USA.
Journal of perinatology: official journal of the California Perinatal Association (Impact Factor: 2.07). 12/2008; 28 Suppl 3:S8-13. DOI: 10.1038/jp.2008.144
Source: PubMed


To use sheep and rat models and demonstrate that stressors activate fetal glucocorticoid (GC) system, corticotrophin-releasing factor (CRF) system and cholinergic neurotransmitter system (ChNS) leading to propulsive colonic motility and in utero meconium passage. Immunohistochemical studies (IHS) were performed to localize GC-Receptors, CRF-receptors and key molecules of ChNS in sheep fetal distal colon. CRF expression in placenta and enteric endocrine cells in fetal rat system were examined and the effects of acute hypoxia on in utero meconium passage was tested. IHS confirmed localization and gestation dependent changes in GC-Rs, CRF-Rs and cholinergic markers in sheep fetal colon. Rat placenta and enteric endocrine cells express CRF and gastrointestinal tract express CRF-Rs. Hypoxia is a potent inducer of meconium passage in term fetal rats. Stress is a risk factor for in utero meconium passage and laboratory animal models can be used to develop pharmacotherapy to prevent stress-induced in utero meconium passage.

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    ABSTRACT: Abstract 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 involving women in presumed preterm labor because of uncertain dates who underwent amniocentesis, and who were later determined to be at term (n=108). The patients were allocated into 2 groups: 1) MSAF group (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) vs. 4.7% (2/42)]. 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) in those with clear amniotic fluid (p<0.001). After heat treatment, the frequency of positive LAL gel clot assay remained higher in the MSAF group [18.1% (12/66) vs. 2.3% (1/42), p<0.05]. Median amniotic fluid IL-6 concentration (ng/mL) was higher in the MSAF group [1.3 (0.7-1.9) vs. 0.6 (0.3-1.2), p=0.04], and median amniotic fluid glucose concentration (mg/dL) was lower [6 (0-8.9) vs. 9 (7.4-12.6), p<0.001], than those with clear amniotic fluid. Conclusion: MSAF at term was associated with increased incidence of MIAC. The index of suspicion for an infection-related process in the post-partum woman and her neonate should be increased in the presence of MSAF. Keywords: amniotic fluid glucose, amniotic fluid white blood cell, fetal bowel function, fetal defecation, fetal diarrhea, interleukin-6, intrauterine inflammation/infection, Limulus amebocyte lysate (LAL).
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