European Journal of Obstetrics & Gynecology and Reproductive Biology
Original ArticleVasoconstrictive activity of meconium stained amniotic fluid in the human placental vasculature
Introduction
Meconium stained amniotic fluid (MSAF) has well known adverse effects on neonatal survival and neurologic outcome in term or post-term infants [1], [2]. In addition, it is an independent risk factor for cerebral palsy among preterm infants, regardless of gestational age [3].
Two possible mechanisms may explain the association between MSAF and fetal or newborn brain damage. A higher incidence of subclinical chorioamnionitis and microbial invasion of the amniotic cavity has been described in patients with MSAF. Therefore the risk of cytokine-induced perinatal ischemic brain damage is increased [4], [5]. Another mechanism may be related to the vasoconstrictive effect of meconium on the feto-placental vasculature [6], [7].
Recently, it has been suggested that meconium or substances within meconium are capable of penetrating and diffusion through Wharton’s jelly and may induce histopathologic vascular changes in human umbilical arteries and veins [8].
The vasoactive effect of meconium on the human umbilical cord and its blood vessels has been previously demonstrated [6], [7], [9]. It is possible that this vasoactive effect may be one of the several primary causes of neonatal complications, such as persistent fetal circulation, necrotizing enterocolitis and renal failure occurring more frequently in conjunction with MSAF. These complications are likely to be initiated as a result of the vasoconstrictive effect of meconium on placenta, umbilical cord, and other fetal vessels [6], [9]. However, no data are available that directly examine the influence of meconium on vascular activity of the feto-placental unit. The aim of this study was to evaluate the effect of meconium on the feto-placental vasculature using in vitro, dually perfused, term placentas.
Section snippets
Materials and methods
Placentas (n=16) from uncomplicated term pregnancies were collected immediately after either vaginal or cesarean delivery. The perfusion experiments were performed using the method of Schneider and Huch [10]. Placentas were taken to the laboratory where a fetal artery and fetal vein from a single cotyledon were cannulated, within 20 min of delivery. Following successful establishment of the fetal circulation, the placenta was mounted in a perfusion chamber, and the maternal circulation was
Results
The mean basal pressure in the control placentas was higher than in the experimental placenta, although it did not reach statistical significance (50.2±10.7 mm Hg versus 48.8±9.7 mm Hg, P=0.8).
Fig. 1 displays the changes in pressure at various optical densities. Bolus infusion of MSAF resulted in a significant dose-dependent increase in perfusion pressure. The MSAF with the highest optical density demonstrated the greatest change in perfusion pressure. (42.8±11.7 mm Hg for OD of 24–35 U/g vs.
Comment
The presence of MSAF is an ominous sign, especially when it occurs in preterm labor and delivery [3], [4]. There is considerable evidence that the presence of meconium in amniotic fluid increases the odds for birth asphyxia, subsequent brain damage and neonatal mortality [2], [6], [7]. Meconium staining of amniotic fluid is reported in 12 to 20% of live births and in many of these cases represents a response of the fetus to the stress of labor [12].
Meconium passage may be in response to hypoxia
Acknowledgments
The authors are grateful to Els and Martin Wyler for sponsoring the establishment of The Placenta Perfusion Laboratory, in which the present study was performed.
References (15)
Relationship of intrapartum and delivery room events to long-term neurologic outcome
Clin. Perinatol.
(1989)- et al.
Meconium stained amniotic fluid and risk for cerebral palsy in preterm infants
Obstet. Gynecol.
(1997) - et al.
Maternal and perinatal outcome of patients with preterm labor and meconium-stained amniotic fluid
Obstet. Gynecol.
(1995) - et al.
Amniotic fluid interleucin-6: a sensitive test for antenatal diagnosis of acute inflammatory lesions of preterm placenta and prediction of preterm morbidity
Am. J. Obstet. Gynecol.
(1995) Can meconium in the amniotic fluid injure fetal brain ?
Obstet. Gynecol.
(1995)- et al.
Amniotic fluid meconium: a fetal environmental hazard
Obstet. Gynecol.
(1996) - et al.
Spectrophotometric determination of meconium concentration in amniotic fluid
J. Biomed. Eng.
(1986)
Cited by (24)
Cerebral palsy and perinatal asphyxia (II - Medicolegal implications and prevention)
2011, Gynecologie Obstetrique et FertilitePlacental Pathology and Cerebral Palsy
2006, Clinics in PerinatologyMeconium aspiration induces oxidative injury in the hippocampus of newborn piglets
2005, Early Human DevelopmentVasoconstrictive activity of oxytocin in meconium impregnated human placentas
2002, European Journal of Obstetrics and Gynecology and Reproductive BiologyIndomethacin activity in the fetal vasculature of normal and meconium exposed human placentae
2001, European Journal of Obstetrics and Gynecology and Reproductive Biology