Maternal Intravenous Administration of Azithromycin Results in Significant Fetal Uptake in a Sheep Model of Second Trimester Pregnancy

Treatment of intrauterine infection is likely key to preventing a significant proportion of preterm deliveries before 32 weeks of gestation. Azithromycin (AZ) may be an effective antimicrobial in pregnancy; however, few gestation age-approriate data are available to inform the design of AZ-based treatment regimens in early pregnancy. We aimed to determine whether a single intra-amniotic AZ dose or repeated maternal intravenous (i.v.) AZ doses would safely yield therapeutic levels of AZ in an 80-day-gestation (term is 150 days) ovine fetus. Fifty sheep carrying single pregnancies at 80 days gestation were randomized to receive either: (i) a single intra-amniotic AZ administration or (ii) maternal intravenous AZ administration every 12 h. Amniotic fluid, maternal plasma, and fetal AZ concentrations were determined over a 5-day treatment regimen. Markers of liver injury and amniotic fluid inflammation were measured to assess fetal injury in response to drug exposure. A single intra-amniotic administration yielded significant AZ accumulation in the amniotic fluid and fetal lung. In contrast, repeated maternal intravenous administrations achieved high levels of AZ accumulation in the fetal lung and liver and a statistically significant increase in the fetal plasma drug concentration at 120 h. There was no evidence of fetal injury in response to drug exposure. These data suggest that (i) repeated maternal i.v. AZ dosing yields substantial fetal tissue uptake, although fetal plasma drug levels remain low; (ii) transfer of AZ from the amniotic fluid is less than transplacental transfer; and (iii) exposure to high concentrations of AZ did not elicit overt changes in fetal white blood cell counts, amniotic fluid monocyte chemoattractant protein 1 concentrations, or hepatotoxicity, all consistent with an absence of fetal injury.     

Tobramycin: Maternal-Fetal Pharmacology

To investigate the maternal-fetal transfer of tobramycin (TBM) and its distribution in the fetus, a single dose of 2 mg/kg was administered intramuscularly to 35 pregnant patients (13 first trimester, 22 second trimester) 0.5 to 34 h before hysterectomy. TBM concentration was assayed microbiologically in maternal serum, fetal tissues (placenta, brain, lung, liver, and kidney), and fluids (amniotic, cerebrospinal fluid [CSF], urine, and serum). Mean maternal serum half-life (1.54 h) and mean peak serum concentration of TBM were within ranges reported for nonpregnant adults. In fetal serum, half-life was 5.2 h, and TBM levels did not exceed 0.58 μg/ml. For intervals up to 34 h, the mean TBM concentration in placental tissues was 1.4 μg/g. Concentration differences related to fetal maturation were found for fetal CSF, amniotic fluid, and fetal kidney. No antimicrobial activity was found in the fetal CSF of >16 weeks' gestation. TBM was present predominantly in the second trimester amniotic fluid specimens. Fetal kidney concentrations reached 7.2 μg/g at 34 h after maternal drug administration. Higher TBM concentrations were related to advanced maturation of the fetal kidney. Second trimester fetal urine concentrations for TBM ranged from 0.1 to 3.4 μg/ml, and the fetal urinary half-life was 3.7 h. Knowledge of fetal pharmacology is essential for weighing the fetal benefits or risks of antimicrobial therapy for the infected gravid patient.     

Pharmacokinetics and pharmacodynamics of labetalol in the pregnant sheep.

The maternal-fetal disposition of labetalol, a combined alpha-1 and beta adrenergic blocker, and its pharmacodynamics in pregnancy are not well understood. This study describes the pharmacokinetics, cardiovascular and metabolic effects of labetalol in the mother and in utero fetus after a 100-mg maternal i.v. bolus administration, in the chronically instrumented pregnant sheep. Labetalol shows a triexponential decline in the mother with a total body clearance of 30.8 +/- 3.83 ml/min/kg, an apparent steady-state volume of distribution (nonparametric) of 3.02 +/- 0.18 liters/kg and terminal elimination half-life of 2.79 +/- 0.66 hr. These estimates are similar to the reported values in pregnant women. Labetalol rapidly crosses the sheep placenta. The peak fetal plasma concentration was 33.7 +/- 5.8 ng/ml, the fetal exposure to labetalol as calculated by the fetal to maternal area under the curve ratio was 14.37 +/- 1.54% and the apparent fetal elimination half-life was 3.71 +/- 0.5 hr. Labetalol persists in the amniotic and fetal tracheal fluids up to 24 hr with concentrations reaching 2- to 4 times the fetal plasma concentration. Whereas there were no significant maternal or fetal cardiovascular effects, some very significant metabolic effects were observed, including fetal and maternal lactic acidosis and hyperglycemia. Lactic acid accumulates in the fetal blood and amniotic fluid with peak concentrations (6.0 +/- 0.31 and 5.5 +/- 0.26 mM, respectively) showing a more than 300% increase over control values. The exact mechanism by which labetalol causes these metabolic effects is not clear, but it may involve its partial beta-2 agonist activity.     

Accumulation and clearance of morphine-3-beta-D-glucuronide in fetal lambs

The time course and extent of morphine-3-beta-D-glucuronide (M3G) production from morphine (MOR) and the clearance of M3G from plasma was studied in the late gestation fetal lamb. MOR was infused at a constant rate into the fetal vena cava and plasma was sampled from the fetus and ewe. Amniotic fluid was also sampled in one animal. M3G was produced in the fetal lamb and accumulated extensively in fetal plasma and amniotic fluid. Seizure activity was observed in two fetal lambs with extremely high plasma concentrations of M3G and MOR. The molar ratio of M3G to MOR in fetal plasma was dependent upon the duration of infusion, reaching a plateau of 60 at about 3 days, but appeared to be independent of the infusion rate over the range studied, 3 to 30 mg hr-1. Maternal plasma MOR and M3G concentrations were substantially less than corresponding fetal plasma concentrations. Using the steady-state plasma concentration of M3G obtained from infusion of MOR and the clearance of M3G derived from single injection of M3G to fetal lambs, the fraction of MOR converted to M3G by the fetus was calculated to be 0.63. Although MOR is conjugated to glucuronic acid in the fetal lamb and excreted into the amniotic fluid it is not readily transferred across the epitheliochorial placenta to the ewe because of restricted permeability.     

Variations of the concentrations of certain glycoproteins in maternal serum, fetal serum and amniotic fluid during pregnancy (author's transl)]

The authors investigated systematically the variations during normal pregnancies of the concentrations of alpha-1-antitrypsin, orosomucoid, transferrin and alpha-fetoprotein simultaneously in maternal serum, fetal serum and amniotic fluid. The role of certain factors such as the gestational age birth weight, placental weight and pairty were studied with regard to variations in the concentrations of each of these proteins. This research permitted the definition during pregnancy of the normal concentrations for these four proteins and allowed us to learn more about protein exchanges between fetal blood, maternal blood and amniotic fluid. There exists a difference between the concentrations of alpha-1-antitrypsin and of orosomucoid found for primigravidae and for multigravidae. The role of these glycoproteins in preventing the mother from rejecting the fetus (insofar as the fetus may be considered as an allograft) is discussed.     

Changes in alpha 1-acid glycoprotein serum concentrations and glycoforms in the developing human fetus.

alpha 1-Acid glycoprotein concentrations and reactivity to concanavalin A were measured in maternal and fetal serum and amniotic fluid obtained from 24 women undergoing diagnostic cordocentesis at 20 to 33 wk gestation and in 30 additional fetal sera (19 to 34 weeks gestation). Maternal alpha 1-acid glycoprotein serum levels were five to ten times higher than fetal and amniotic levels. Fetal alpha 1-acid glycoprotein levels were found to increase with advancing gestational age. Using crossed immunoaffino electrophoresis with concanavalin A, alpha 1-acid glycoprotein patterns were identical in maternal serum and amniotic fluid but totally different in fetal serum. The fetal concanavalin A pattern changed progressively during fetal life towards that of the newborn. These data confirm earlier assumptions of fetal synthesis of alpha 1-acid glycoprotein and provide normal reference values for alpha 1-acid glycoprotein in fetal serum. In addition, the specific fetal concanavalin A pattern indicates that the alpha 1-acid glycoprotein glycosylation process during fetal life differs from that in post-natal life.     

Urinary excretion of meperidine by the fetal lamb.

The renal excretion of meperidine by the fetus was determined in five chronic, unanesthesized fetal lamb preparations. Chronic indwelling catheters were implanted in the maternal aorta and vena cava, the fetal aorta, amniotic sac and allantoic sac. Via laparotomy, two catheters were implanted in the fetal bladder; the urachus and urethra were ligated. After intravenous administration of 2.5 mg/kg to the mother, meperidine rapidly appears in fetal urine. Approximately 0.02 to 0.05% of the maternal dose was excreted into fetal urine as unchanged meperidine in 300 min. The elimination half-life of meperidine in the fetus is 32.6 +/- 3.7 min when calculated from the urinary excretion rates, and 28.6 +/- 3.9 min when estimated from the plasma decay curve. The renal clearance of meperidine by the fetus ranged from 2.8 to 16.7 ml/min. Although the urachus and urethra were ligated, meperidine is found in samples of amniotic and allantoic fluid, indicating that the drug can diffuse across the placental membranes from the mother into these fluids. We have demonstrated that renal elimination of meperidine is a route of drug elimination by the fetus. These data support a pharmacokinetic model that describes the disposition of meperidine in the maternal-fetal unit by use of a two-compartment open model with elimination from both maternal and fetal compartments.     

Effect of zidovudine on transplacental pharmacokinetics of ddI in the pigtailed macaque (Macaca nemestrina).

Since zidovudine and ddI may be used in combination in the future to treat pregnant women who are human immunodeficiency virus positive, we conducted a study to determine whether zidovudine affects the transfer of ddI across the placenta. Zidovudine and ddI were infused simultaneously to three near-term pregnant macaques (Macaca nemestrina) at 156 +/- 1.5 days of gestation. Samples of maternal and fetal blood and amniotic fluid were drawn at intervals for 30 h. The steady-state dideoxyinosine concentrations in the plasma of the dam (Cssd), the fetus (Cssf), and the amniotic fluid (Cssa) and the ratios Cssf/Cssd and Cssa/Cssf were found to be not significantly different from the values previously determined after the administration of ddI alone during the same pregnancy. We conclude that concurrent zidovudine administration does not affect the transfer of ddI across the placenta in near-term Macaca nemestrina.     

Fetal insulin and growth hormone metabolism in the subhuman primate

The concentrations of plasma glucose, insulin, growth hormone, and immunoreactive growth hormone-like substance in subhuman primate fetal and maternal plasma were examined after the intravascular administration of glucose, arginine, or tolbutamide to the fetus. Cannulation of interplacental vessels permitted studies on the fetus in utero without disruption of fetal-placental-maternal anatomic integrity. Single glucose injections, glucose infusions, and arginine infusions into the fetus did not alter fetal plasma insulin concentrations. In contrast, tolbutamide injections elicited an immediate 3-4-fold increase in fetal plasma insulin concentrations. A bidirectional placental transfer of insulin was demonstrated with the use of simultaneously injected insulin-(125)I to the mother and insulin-(131)I to the fetus.Simian fetal plasma contained a substance which cross-reacted with immunologic identity to human growth hormone. In contrast, simian maternal plasma and amniotic fluid reacted with immunologic nonidentity to human growth hormone. Although glucose administration to the fetus did not suppress nor did arginine infusion consistently augment fetal plasma growth hormone levels, the latter were observed to vary in individual experiments.The plasma responses to the same stimuli in the neonate were also examined. In contrast to the fetal experiments, glucose injection in the neonate elicited a delayed rise in the concentration of plasma insulin. Similar to the fetus, the plasma concentration of insulin increased after tolbutamide injection and did not change in response to arginine infusion. The initial concentrations of neonatal plasma growth hormone were significantly lower when contrasted with the initial fetal plasma levels. There was no difference in the responsiveness of the fetal and neonatal growth hormone-releasing mechanisms when challenged by glucose or arginine infusion.The data indicate that the fetal plasma concentration of growth hormone is labile, that fetal growth hormone metabolism may differ from that in the neonate, and that pancreatic islet cell responsiveness rapidly changes after delivery.     

Unconjugated pteridines in amniotic fluid during gestation

Neopterin and biopterin concentrations were measured in amniotic fluid in 226 pregnancies from the 12th week of gestation to term. At mid-gestation, neopterin and biopterin levels were low and remained relatively constant between 12 and 26 weeks of gestation, whereas during the third trimester, a progressive increase was observed. Near term the values were greater than those in maternal serum and the higher neopterin to biopterin ratio suggested that pteridine concentration in amniotic fluid may reflect the maturation of pteridine metabolism in the fetus.     

Exhaled nitric oxide concentration and amniotic fluid nitrite concentration during pregnancy

Abstract. We have assessed fetal and maternal nitric oxide (NO) production in pregnancy. Exhaled NO and amniotic fluid nitrite concentrations were measured by chemiluminescence between 10 and 42 weeks of pregnancy. Exhaled NO concentrations did not alter significantly during gestation. In contrast, there was a significant change in mean amniotic fluid nitrite concentration in late pregnancy ( P < 0.001). The finding of decreased amniotic nitrite concentrations after 37 weeks of gestation support the hypothesis that reduced NO production may contribute to increased uterine activity in late pregnancy.     

Monoamine-oxidizing enzymes in human pregnancy

The activity of benzylamine oxidase (BzAO) was investigated in human maternal blood at all stages of gestation, including parturition, as well as in the puerperium. In addition, BzAO and monoamine oxidase (MAO) A and B activities were assayed in amniotic fluid, placenta, placental vessels and umbilical vessels. No correlation was found between BzAO values in maternal blood and fetal growth. Highly significant variations in maternal plasma BzAO activity were seen by the end of the first trimester, at parturition and at 6–72 h post-partum.

The predominance of MAO A in placenta was again confirmed, whereas in vascular tissue and amniotic fluid, BzAO was clearly preponderant; in the latter, no MAO A activity could be detected. Placental vessels showed significantly higher MAO A activity than umbilical vessels. BzAO and what appears to be a true, soluble MAO B were demonstrated in amniotic fluid.

The physiological implications of these findings are discussed.     

Illumina测序技术在母血检测胎儿非整倍体中应用

目的研究Illumina测序技术在母血中检测胎儿非整倍体的可行性,及其在无创性产前诊断中的应用前景。方法 68例孕12-39周具有产前诊断指征的单胎妊娠孕妇抽取外周血进行离心、提取血浆中游离DNA,运用Illumina Hiseq2000测序技术进行DNA测序及统计分析。结果 68例孕妇通过Illumina测序技术检测出3例21三体,2例18三体、1例13三体及1例47,XYY。因为濒死胎儿羊水脱落细胞活力极低而致羊水培养失败,传统型染色体核型分析未检测出1例21三体。结论 Illumina测序作为一种无创性产前诊断技术,可准确地筛查21、18、13、X、Y等染色体非整倍体异常,具有安全、准确率高及假阳性率低的优点,值得临床推广。     

Pharmacokinetics of spiramycin in the rhesus monkey: transplacental passage and distribution in tissue in the fetus.

Transplacental transfer of spiramycin was investigated in a rhesus monkey model to study whether the antibiotic reaches therapeutic levels in the fetus. Spiramycin concentrations were measured by bioassay and high-performance liquid chromatography. Pharmacokinetic parameters were determined for bioactive spiramycin as measured by the bioassay. Pharmacokinetic pilot studies showed that spiramycin distribution follows a two-compartment model in rhesus monkeys. Following a single intravenous dose of 50 or 250 mg, dose-dependent kinetics were observed. At a dose of 50 mg, 10% of the dose was excreted unchanged in the urine. At the higher dose of 250 mg, an oliguric effect was observed. Spiramycin concentrations in fetal serum were measured over time while the maternal concentration was maintained at a constant level. During a 5-h experiment, a maximum fetal-maternal serum ratio of 0.27 was found. In three fetuses, concentrations in serum and tissue were measured following intravenous administration of 50 mg of spiramycin twice daily to the mother for at least 7 days. The fetal-maternal serum ratios were found to be 0.4 to 0.58 after intravenous administration of the final dose of 50 mg to the mother. It appeared that spiramycin accumulated in the soft tissues, especially in the liver and spleen, of both the mother and the fetus. The concentration in placental tissue appeared to be 10 to 20 times that of the concentration in fetal serum. The concentration of spiramycin in amniotic fluid was about five times higher than the concentration in fetal serum. Another important observation was that absolutely no spiramycin was found in the brain.     

Ceftriaxone distribution between maternal blood and fetal blood and tissues at parturition and between blood and milk postpartum.

The penetration of ceftriaxone into the fetus at parturition was studied in 17 subjects. Despite its high protein binding, ceftriaxone quickly reached the umbilical cord blood, amniotic fluid, and placenta, achieving substantial concentrations, which then disappeared, with elimination half-lives of approximately 6 h, identical to that of the mother. The elimination half-life of ceftriaxone of 5 to 6 h in these mothers was somewhat shorter than that reported for normal subjects. The concentrations of ceftriaxone achieved in fetal tissues were sufficient for therapeutic effects. The penetration of ceftriaxone into milk was studied 3 days postpartum in 20 other patients. This antimicrobial agent entered breast milk rapidly and disappeared with a half-life of 12 to 17 h. The concentrations achieved were only 3 to 4% of those in maternal serum and were most likely of little clinical relevance.     

Effectiveness of spiramycin for treatment of congenital Toxoplasma gondii infection in rhesus monkeys.

The effectiveness of spiramycin for the treatment of rhesus monkey fetuses congenitally infected with Toxoplasma gondii was studied. Eight monkeys were infected at day 90 of pregnancy. This is comparable to the second trimester of organogenetic development in humans. Transmission of infection was found prenatally in five of the eight monkeys by detection of the parasite in the amniotic fluid. Treatment with spiramycin (20 mg/kg/day in two intermittent doses given intravenously) was started as soon as fetal infection was proven and was continued until birth. Nine to 14 days after initiation of treatment, the parasite was still detectable in amniotic fluid samples from four of these five cases. However, the parasite was detected only by PCR and not by mouse inoculation. T. gondii was also detected only by PCR in the placenta of one monkey that delivered prematurely. This monkey received spiramycin treatment for only 2 weeks. In the four monkeys that received treatment for about 7 weeks, the parasite was not present at birth in the placenta nor in amniotic fluid or neonatal organs. Spiramycin accumulates mainly in maternal tissues. Although concentrations in neonatal tissue were found to be 5 to 28 times higher than the corresponding concentrations in neonatal serum, the concentrations in neonatal tissue were still 11 to 16 times lower than those found in the mothers. However, no spiramycin was found in the fetal brains. Early treatment with spiramycin may prevent transmission of infection to the fetus but most probably cannot interrupt an existing brain infection, which is the most severe outcome of congenital toxoplasmosis in humans.     

Exchange of carbon dioxide in the pregnant rhesus monkey: multicompartmental analysis of carbon dioxide kinetics

The exchange of carbon dioxide in the pregnant rhesus monkey has been studied quantitatively using sodium bicarbonate-(14)C and applying the model of a system of seven compartments. The transfer rates among the various compartments, compartment sizes, and the rate of production of carbon dioxide by fetus and mother were determined with a computer programmed to fit the theoretical model to the data by adjusting the parameter values of the model until a "best fit" was obtained. It was confirmed that the exchange of carbon dioxide between fetal and maternal blood across the placenta is rapid, that between fetal blood and amniotic fluid is slow, and that there is no appreciable exchange between maternal blood and amniotic fluid. The mean net production of CO(2) by fetus was 0.476 +/-0.0402 mmoles/kg.min, and that by mother was 0.373 +/-0.0279 mmoles/kg.min.     

Fetal syphilis: correlation of sonographic findings and rabbit infectivity testing of amniotic fluid

Fetal syphilis is the presumed diagnosis when the sonographic findings of fetal hydrops are found in the presence of maternal syphilis. In the absence of fetal hydrops, the diagnosis of fetal infection is difficult. We hypothesized that intra-amniotic infection would be accompanied by anatomic placental and fetal abnormalities that could be detected by ultrasonography. Rabbit infectivity testing (RIT), intratesticular inoculation of rabbits with amniotic fluid, can be used to confirm intra-amniotic infection with Treponema pallidum. Twenty-one gravidas with untreated early (primary, secondary, and early latent) syphilis underwent sonography and amniocentesis for RIT at 24 weeks of gestation or later. Antenatal sonographic findings were compared to their amniotic fluid RIT results. Hepatomegaly was significantly (P < 0.01) associated with amniotic fluid infection detected by RIT. Antenatal detection of hepatomegaly, which is probably the initial sonographic manifestation of hydrops fetalis, may ultimately identify the fetus affected with congenital syphilis.     

Cocaine pharmacokinetics in the pregnant guinea pig

The pharmacokinetics of cocaine (COC) were studied during late gestation in guinea pigs. Clearance (Cl) was not dose-dependent and the average +/- S.D. was 59 +/- 16 ml/min/kg over the i.v. dose range of 2 to 12 mg/kg. Volume of distribution at steady state (Vdss), mean resident time (MRT) and elimination half-life (T1/2) were dose-dependent over this dose range with changes occurring between the 2 and the 4 mg/kg dose of COC. Vdss was 2.1 and 3.9 l/kg. MRT time was 42 and 57 min, and elimination T1/2 was 34 and 49 min at the 2 and 4 mg/kg dose, respectively. Cl and Vdss values after 2 to 20 mg/kg of COC s.c. were similar to those after i.v. administration, whereas MRT was significantly greater as a result of delayed absorption. Absorption of COC s.c. was nearly complete (84%) and had a T1/2 of 51 min. Benzoylecgonine (BE) and benzoylnorecgonine (NOR) were major and persistent metabolites of COC. Norcocaine was present after COC doses of 4 mg/kg or higher but could only be detected during the first 2 hr.     

Effects of gestational age on the disposition of propranolol in pregnant sheep

Maternal and fetal disposition of the beta adrenoceptor blocking drug, propranolol was examined in the pregnant sheep from day 95 to day 140 (term, 145 days) of gestation. Propranolol was administered to the mother (bolus dose, 1.5 mg/kg followed by an infusion of 1.2 mg/kg/hr over 3 hr) to achieve an average steady-state maternal total drug concentration of 600 ng/ml. Total steady-state maternal plasma propranolol concentration was 666 +/- 266 ng/ml, reflecting a 4-fold variation in maternal drug clearance and a 14-fold variation in binding. Neither maternal clearance nor binding showed a significant change with gestational age. Total plasma drug concentrations in the fetus increased significantly with gestational age (r = 0.58, P less than .05), due to a concomitant increase in binding (r = 0.66, P less than .01). Fetal steady-state unbound drug concentrations were 50% of those seen in the mother, indicating that the fetus is capable of irreversible elimination of the drug. This ratio did not change with gestational age, suggesting that the capacity of the fetus to eliminate propranolol does not increase detectably in the latter part of pregnancy. The significant correlation between maternal and fetal unbound drug concentrations indicates that a major determinant of fetal exposure to propranolol is the clearance of the drug by the mother.