Amnionic fluid D(-)- -hydroxybutyrate and the dysmature newborn infant

Effect of maternal ketoacidemia on the pregnant ewe and the fetus

Poorly controlled diabetic pregnancies are associated with hyperglycemia and elevated ketones. While glucose is known to cross the placenta, there is limited information regarding the placental transfer of ketones and their associated cardiovascular and metabolic effects in the fetus. Thus, the present study was undertaken to evaluate the transfer of the ketoacid beta hydroxybutyrate across the ovine placenta and to determine the effects of this ketoacid on maternal and fetal physiologic and metabolic parameters. Pregnant ewes (110 to 120 days' gestation) were instrumented with catheters in the lateral branch of both uterine arteries, uterine veins, femoral artery, and femoral vein, and electromagnetic flow probes were placed on both middle uterine arteries. Catheters were placed in the fetal carotid artery and jugular vein, and a catheter and balloon were placed in the amniotic fluid. Beta hydroxybutyrate (0.39 mmole/100 ml of uterine blood flow) and antipyrine (00.27 mmole/100 ml of uterine blood flow) as a second reference marker, were infused simultaneously into the uterine arteries for a period of 2 hours. The beta hydroxybutyrate concentrations in the uterine vein increased to 5.93 +/- 1.32 mmoles/L, and were associated with a significant increase in maternal heart rate and a slight but significant reduction in uterine blood flow. No changes in maternal arterial blood gas values were noted. The concentration of beta hydroxybutyrate in the fetal carotid arteries increased from 0.01 +/- 0.01 mmole/l to 0.15 +/- 0.03 mmole/L, and were associated with a significant reduction in fetal PaO2 (24.2 +/- 0.9 to 17.9 +/- 1.9 mm Hg) and an elevation of fetal lactate levels (1.86 +/- 0.17 to 5.07 +/- 1.56 mmoles/L).

Comparison of human and sheep chorion laeve permeability to glucose, beta-hydroxybutyrate, and glycerol

Significant permeability of in vitro human chorion laeve to glucose, glycerol, and beta-hydroxybutyrate (betaOH butyrate) and in vitro sheep chorion leave to glycerol and betaOH butyrate was measured. Diffusion across these tissues of glycerol and betaOH butyrate corresponded to the relative molecular size, charge, and lipid solubility of these compounds. The simple diffusion of glucose across human chorion leave was somewhat reduced by metabolic conversion of this compound during the transfer process. Demonstration of in vitro human placental tissue permeability to ketoacids and glycerol suggests that these compounds cross to the fetus when elevated in the maternal diabetic state.

Changes in amniotic fluid glucose, beta-hydroxy-butyrate, glycerol, and lactate concentration in diabetic pregnancy

Amniotic fluid glucose, beta OH butyrate, glycerol, and lactate concentrations were measured in 75 samples collected in the third trimester of pregnancy from 50 diabetic patients, all but four of whom required insulin. Increases in maternal fasting plasma sugar were accompanied by corresponding increases in amniotic fluid glucose and on occasion increases in amniotic fluid beta OH butyrate. These data correspond to previous reports of placental glucose transfer and in addition, provide statistically significant evidence of placental betaOH butyrate transfer since the hyperglycemic, hyperinsulinemic fetus of a diabetic mother would be a poor primary source for ketogenesis. Relatively poor correlation of elevated fluid levels of these solutes to fetal outcome probably reflects a low incidence of maternal hyperglycemia, ketogenesis. Relatively poor correlation of elevated fluid levels of these solutes to fetal outcome probably reflects a low incidence of maternal hyperglycemia, ketoacidosis, and over-all reduced neonatal morbidity-mortality rates in this group of metabolically well-controlled, predominantly insulin-requiring diabetic patients managed in a regional high-risk perinatal center.

Substrate mobilization: a new hypothesis for the aetiology of the idiopathic respiratory distress syndrome

This hypothesis for the aetiology of the idiopathic respiratory distress syndrome of the newborn (IRDS) proposes that, although the aetiology is multifactorial, the factor of prime importance is the mobilization of substrate for surfactant synthesis. All factors known to influence the incidence, treatment, and prognosis of the IRDS can be shown to be associated with the mobilization of substrate and thereafter its continued availability for the synthesis of adequate surfactant. Thus factors which promote an antenatal increase in the breakdown of energy stores will be associated with a reduced incidence of the IRDS. On the other hand, despite adequate mobilization, factors associated with a lack of substrate secondary to poor transport of substrate, a reduction in pulmonary circulation or an alteration in fetal or neonatal metabolism which involves an increased utilization of substrate to provide energy, will be associated with an increased incidence of the IRDS.