Premature labor. II. Bacterial sources of phospholipase.

Human term labor is thought to be initiated by amniotic and chorionic phospholipase A2, an enzyme that liberates arachidonic acid esters from the phospholipids of these membranes, leading to the synthesis of prostaglandins by the placental membranes. The striking association of premature labor with intrauterine infection or contamination, urinary tract infection, and early neonatal sepsis led us to study the microorganisms present in these infections for phospholipase A2 activity. Activity was found in Bacteroides fragilis, Peptostreptococcus, Fusobacterium necrophorum, Streptococcus viridans, Streptococcus fecalis, Streptococcus A and B, Escherichia coli, Klebsiella, Staphylococcus epidermidis, Pneumococcus, Lactobacillus, and Mycoplasma hominis. Bacteroides fragilis, Peptostreptococcus, Fusobacterium, and S viridans had the highest activities. The specific activities of phospholipase A2 from these organisms were several times higher than that of the membrane phospholipase A2 of the amnion and chorion. We postulate that premature labor may be initiated by microorganisms with phospholipase A2 activity from endocervical and/or intrauterine contamination or infection, producing deacylation of arachidonic acid from amniotic phospholipids with increased concentrations of free arachidonic acid and increased prostaglandin synthesis, which triggers labor.

Premature labor. I. Prostaglandin precursors in human placental membranes.

Amnion and chorion from premature and term placentas after both spontaneous labor and elective cesarean section were assayed for phospholipids and fatty acid composition by 2-dimensional thin-layer chromatography and gas-liquid chromatography. In preterm placental phospholipids, phosphorus concentrations were higher in amnion than in chorion, whereas at term the membranes were similar owing to an increase in phospholipid concentration in the chorion late in gestation. PHosphatidylcholine (PC) accounted for 47% of the total phospholipid phosphorus, followed by sphingomyelin at 20%, phosphatidylethanolamine (PE) at 15%, phosphatidylserine (PS) at 12%, and phosphatidylinositol (PI) at 5%. These percentages were similar for amnion and chorion and they did not change during gestation. The percentage of arachidonic acid (AA) was higher in PS (40 to 65%) than in PE (30 to 53%) and PC (10 to 13%). The percentage of AA was significantly higher in PC, PE, and PS from the amnion in premature pregnancies than in those of the premature chorion. At term, these amnionic and chorionic phospholipids had similar concentrations of AA owing to a significant increase in AA in the chorion late in gestation. Amnionic PE from term and preterm elective cesarean section had a significantly higher percentage of AA than that from preterm and term labor. These data suggest that AA is consumed during labor and that amnionic phospholipids, particularly PE, may be its principal source. The amnion seems to be more important for the storage of AA than the chorion, particularly in preterm pregnancies in which the concentrations of phospholipids and the percentages of AA in PC, PE, and PS were significantly higher than in the chorion.

Alterations in fetal lung phosphatidylinositol metabolism associated with maternal glucose intolerance.

Prior to conception, female rabbits were made hyperglycemic by streptozotocin administration. Fetal hyperglycemia and hyperinsulinemia were documented. Although plasma myoinositol concentration were higher in the fetuses of diabetic mothers, the ratio of lung to plasma myoinositol concentrations in 29-day fetal rabbits were lower than control values. CDP-diglyceride:inositol phosphatidyltransferase was reduced by 70% in the diabetic fetuses and their lung tissue phosphatidylinositol content was decreased.

Diagnosis and follow-up of intraventricular and intracerebral hemorrhages by ultrasound studies of infant's brain through the fontanelles and sutures.

A technique to diagnose subependymal hemorrhage (SEH), intraventricular hemorrhage (IVH), intracerebral hemorrhage, and posthemorrhage hydrocephalus in tiny infants, using real time ultrasound studies of the brain ventricular system, is described. This is a bedside technique that visualizes the brain through the fontanelles and the sutures, in three planes: coronal, sagittal, and horizontal. Excellent visualization of the ventricular system, caudate nuclei, the thalamus, the choroid plexus, the corpus callosum, and the foramen of Monro is obtained. This method has good definition using high frequency transducers since there is no bone interference. The ultrasound diagnosis correlated well with computed tomography (CT) and with direct pathologic studies. This technique was more sensitive in diagnosing small IVH/SEH and organized clots than were CT studies. IVH/SEH were found in 90% of 113 infants less than or equal to 34 weeks of gestation; 49% of the hemorrhages were large and 41% were small. Most hemorrhages were found in the first scan, usually shortly after birth. Twenty-one premature infants who never had perinatal asphyxia or respiratory distress syndrome had IVH/SEH. The hemorrhages were followed until disappearance, usually in one to three months in cases of large hemorrhages.

Determination of disaturated lecithin in rhesus monkey amniotic fluid as an index of fetal lung maturity.

Although increased concentrations of total lecithin in amniotic fluid allow prenatal assessment of fetal lung maturation, it has become clear that routine use of the L/S index may lead to a substantial number of inaccurate predictions. Since disaturated lecithin (DL) is a more specific marker of pulmonary surfactant than total lecithin, we developed a convenient method for measuring this phospholipid in amniotic fluid, and then evaluated its level in pregnant rhesus monkeys of 120 to 163 days of gestation. The method involves osmic acid destruction of unsaturated lipids, chromatographic isolation of disaturated lecithin, and quantitation by phosphorus assay. It can be performed in approximately 5 hours on 4 ml. of amniotic fluid and yield 67 +/- 3 per cent average recovery of added 14C-dipalmitolyl lecithin. The results of analyzing 36 rhesus amniotic fluid specimens showed the disaturated lecithin and the disaturated lecithin/sphingomyelin ratio (DL/S) increase sharply after 150 days of gestation, consistent with the pattern of lung maturation in this species. We conclude that disaturated lecithin can be readily quantitated in primate amniotic fluid and that its concentration, the DL/S ratio, and percentage of disaturated lecithin are potentially useful indices of fetal lung maturity for the clinical laboratory.

Heart rate in fetuses and neonates in normal conditions and with mild depression.

The continuous recording of fetal and neonatal heart rate gives reliable information on the condition of the fetus and neonate. In the present study the results obtained in vigorous and mildly depressed newborns, by the continuous recording of fetal heart rate during labor and of neonatal heart rate during 90 minutes after birth, are presented. Twenty three pregnant women were studied during labor, as well as their newborns. They fulfilled the following conditions: --Mothers without known complications and good prenatal care. --Term pregnancies with single fetuses in vertex presentation with birthweight normal for age. --All labors started, progressed and delivered spontanously withoug signs of fetal distress. No drugs were given to the mother during labor or to the neonate. The umbilical cord was clamped immediately after birth. Seventeen neonates were vigorous at 1 and 5 minutes (Apgar score 7 or higher). Six neonates were slightly depressed at the first minute but all of them recovered at 5 minutes. Both groups are studied separately. Figure 1 shows the average values of BFHR and NHR corresponding to 17 vigorous newborns (Apgar scores 7-10 at the first and fifth minutes of life). No major variations were found in the average values of BFHR in the time period studied. No statistically significant differences were found in the BFHR of the same fetus at 60, 30 and 8 minutes before delivery (Fig. 2). A decrease in BFHR occurred during the 6 minutes preceding birth (fig. 1). After birth the average values of NHR were higher than the fetal ones (Fig. 1). This post-natal increase in heart rate (32 beats/min) is statistically significant when BFHR values 30 minutes before delivery are compared with NHR values recorded 10 minutes after birth (Fig. 3). After this initial increase, NHR starts a gradual fall, lasting about 50 minutes and then becomes stable at a level similar to that of fetal heart rate (Fig. 1). Figure 1 shows that puncture of the heel causes an increase in NHR. The difference between NHR before and after the puncture is significant (Fig. 6). The heart rate of 6 newborns which were slightly depressed at the first minute of life (Apgar score 4-6) but vigorous at the fifth minute, are not significantly different from those of the vigorous group of 17 neonates (Fig.7). The cases chosen for this study have been carefully selected with the aim of establishing the "normal" pattern of fetal and neonatal heart rate. We concluded that in normal term labors BFHR remains stable from 90 until 10 minutes before delivery; there is a tendency to fall during the last 6 minutes preceeding birth. Immediately after birth, neonatal heart rate rises significantly, then falls gradually and becomes stabilized 50 minutes after delivery, at levels similar to those of BFHR.