Perinatal outcome of quadruplet pregnancies in relation to chorionicity.

OBJECTIVE: To compare the perinatal outcome of quadruplets in relation to chorionicity. PATIENTS AND METHODS: In this retrospective study, the maternal, neonatal and chorionicity data were collected from 24 sets of quadruplet pregnancies delivered between January 1985 and December 2001. Perinatal and neonatal data were evaluated in relation to chorionicity. RESULTS: Sixteen pregnancies were quadra-chorionic quadramniotic (QC) and eight had at least one monochorionic pair (TC). The median gestational age at delivery was 31 weeks (23 to 34 weeks) with overall perinatal mortality rate of 177 per 1000 total birth. Delivery before 30 weeks (OR 89; 95% CI 9 to 607; P<0.01) and discordant birth weight of >25% (OR 7.6; 95% CI 2 to 29; P<0.01) had independent effects on perinatal loss rate. The perinatal loss was five fold higher in TC quadruplets than those of QC (OR 5.1; 95% CI 1.7 to 15.4; P<0.001). This was attributed to higher risk of very low birth weight (69 vs 13%; P<0.01), delivery before 30 weeks (63 vs 13%; P<0.001) in TC quadruplets compared to QC gestation. CONCLUSIONS: The quadruplets with MC pair have 5 times higher perinatal mortality than quadra-chorionic quadruplet pregnancies owing to preterm delivery and discordant birth weight.

Ontogeny of endogenous secretion of immunoreactive-thyrotropin releasing hormone by the human placenta.

We studied endogenous production of immunologically active TRH (ir-TRH) by human placenta throughout gestation. Fragments (20 g) of placentae obtained between 7 and 41 weeks' gestation were incubated in TC-199 media with or without TRH degrading enzyme inhibitors (1 mM of dithiothreitol, 200 microm O-phenanthroline, 0.8 mM EDTA) at 37 C for 24 h. TRH was quantitated by RIA. Release of ir-TRH was also studied in an in vitro model of dually-perfused isolated lobule of human term placenta. Cellular localization of TRH was performed by staining early-, mid- and late-gestation placentae with anti-TRH rabbit polyclonal antibody, using the indirect avidin-biotin complex immunoperoxidase method. TRH was produced by placental fragments from 7 to 41 weeks' gestation. Placental TRH secretion was maximal between 7-12 weeks gestation both in presence (655 +/- 79 pg/10 mg protein) and absence (423 +/- 75 pg/10 mg protein) of enzyme inhibitors. Secretion of TRH declined with increasing gestation both with (y = 779 - 15x; r = 0.90; P < 0.001; n = 15) and without (y = 525 - 12x; r = 0.87; P < 0.001; n = 15) enzyme inhibitors. In the perfusion experiments, endogenous TRH was released predominantly into the fetal circulation, and its concentration was markedly higher in the presence of enzyme inhibitors (146 +/- 27 vs. 34 +/- 7 pg/mL; P < 0.001). Immunostaining of chorionic villi localized TRH to the cytoplasm of the syncytial layer, and the intensity declined with advancing gestational age. These data suggest that immunoactive TRH is produced by human placenta begin at 7 weeks gestation, and production declines with gestational age.

Transfer and metabolism of thyrotropin releasing hormone across the perfused human term placenta.

The transport and uptake of TRH was investigated in the maternal-fetal-placental unit of perfused human term placenta. The degradation of TRH in biological fluid was first determined by incubating [125I]TRH with 100 microL 50% maternal or cord sera with or without pretreatment with 200 microM of p-hydroxymercuriphenyl sulfonic acid (p-HMSA), a proline dipeptidase inhibitor. Transplacental transfer of TRH was then studied by adding 10 microCi of [125I]- or [3H]TRH to the maternal circulation of dually perfused isolated lobule of human term placenta with or without 200 microM p-HMSA. Creatinine was used as an internal marker. The rate of degradation of TRH (P < 0.001) and inhibition by p-HMSA were significantly higher in maternal than cord sera (P < 0.05). In the maternal circulation, TRH concentration declined rapidly from 100% at time 0 to 33.5 +/- 1.2% at 120 min. The fetal concentration increased from undetectable levels to a maximum of 1.8 +/- 0.3% at 120 min with a low feto-maternal ratio (0.08 +/- 0.02). Perfusion in the presence of p-HMSA, however, did not significantly change fetal concentration, or the maternal and fetal concentration-time integral levels of TRH. Chromatography of maternal, fetal, and placental homogenates showed that TRH was metabolized by the placenta into small molecular weight fragments predominantly released in the maternal circulation. These results suggest that human placenta acts as an enzymatic barrier to the free passage of TRH.

Liposomal thyroxine: a noninvasive model for transplacental fetal therapy.

Drugs that cross the placenta sparingly are currently given directly to the fetus by invasive procedures. We investigated whether anionic small unilamellar (SUV) liposomes of different lipid compositions enhanced the transfer and uptake of T4 in an in vitro model of perfused human term placenta. T4-encapsulated anionic liposomes were prepared using lecithin (F-SUV) or distearoyl phosphatidylcholine (S-SUV) with cholesterol and dicetylcholine. The size distribution, encapsulation efficiency, and stability were determined in blood-based media. The transfer kinetics of free and liposomally encapsulated T4 were studied in a dually perfused isolated lobule of human term placenta, with creatinine and liposomal carboxyfluorescein as marker substances. Concentrations of T4 and rT3 were measured by RIA. T4 crossed the placenta sparingly (1.9 +/- 0.5%) because it was metabolized to rT3 (9.2 +/- 1.3%). Transplacental transfer of T4 was significantly increased by F-SUV (15.8 +/- 2.1%; P < 0.001) and S-SUV liposomes (7.1 +/- 1.2%; P < 0.001), with a concomitant decrease in fetal rT3 levels (P < 0.001). Placental uptake of F-SUV (13.5 +/- 2.0%; P < 0.001) was greater than that of S-SUV liposomes (6.7 +/- 0.8%; P < 0.001). Our data suggest that anionic liposomes increase transplacental transfer of T4. If confirmed in vivo, liposomes may provide an alternative noninvasive method of drug delivery to the fetus.

Transport and metabolism of thyrotrophin-releasing hormone across the fetal membrane.

To determine the transfer and metabolism of TRH by human fetal membranes, the bidirectional transport and uptake of TRH was investigated by adding 125I-labeled TRH (100,000 cpm) or commercial TRH either to the maternal or the fetal compartment of an in vitro model of cultured human fetal membranes obtained from term and preterm placenta. Transmembrane transfer was also studied in the presence of 200 microM p-hydroxy-mercuriphenyl-sulphonic acid (p-HMSA), a dipeptidase enzyme inhibitor. Creatinine and heparin were used as an internal markers. Metabolites of TRH were separated from intact molecules by gel filtration on Sephadex G-10. The structural integrity of the membrane was confirmed by electron microscopy. The transmembrane transfer of radiolabeled and commercial TRH were comparable across both preterm and term placenta. When transport was studied from the maternal to fetal side, the maternal concentration of TRH declined rapidly from 100% at time 0 to 19.31 +/- 2.26% at 8 h with a concomitant increase in the fetal concentration from undetectable to a maximum of 2.56 +/- 0.38% with a fetomaternal ratio of 0.16 +/- 0.01. Transfer of TRH from the fetal to maternal compartment was similar to that of maternal to fetal. Chromatography of maternal and fetal media showed that TRH was metabolized by the membrane into small molecular weight fragments. Treatment of the membrane with p-HMSA increased TRH transport from the maternal to fetal compartment to 18.12 +/- 0.91 (P < 0.001) with an fetomaternal ratio of 0.35 +/- 0.02 (P < 0.001). Although transmembrane transfer of TRH from the fetal to maternal side was also increased by p-HMSA, levels achieved were less than that from maternal to fetal (12.26 +/- 1.50%; P < 0.05). These results suggest that the human fetal membrane acts as an enzymatic barrier to the bidirectional transfer of TRH from 24 weeks gestation.

Placental regulation of insulin-like growth factor axis in monochorionic twins with chronic twin-twin transfusion syndrome.

To test the hypothesis that severe growth restriction (intrauterine growth retardation) in donor twins with chronic twin-twin transfusion syndrome (TTTS), a common complication of monochorionic twin pregnancy, is due to an aberration in the insulin-like growth factor (IGF) axis, we studied 25 sets of monochorionic twins with (n = 13) and without (n = 12) TTTS. Maternal and cord blood samples were collected at birth and analyzed for IGF-I, IGF-II, IGF-binding protein-1 (IGFBP-1), and IGFBP-1 phosphorylation status. Fetal IGF-II levels in the recipient twins with TTTS were higher than those in the donor twins (829 +/- 45 vs. 543 +/- 60 ng/mL; P < 0.001), but were comparable with those in the non-TTTS twin pairs. IGF-I levels in recipient and donor twin pairs were similar. The total IGFBP-1 concentration was higher in the donor twins than in the recipients (1153 +/- 296 vs. 419 +/- 108 ng/mL; P < 0.001) and non-TTTS twin pairs (P < 0.01). The percent less phosphorylated IGFBP-1 was higher in the recipients than in the donor twins (P < 0.05). There were no differences in IGF-I, IGF-II, and IGFBP-1 levels between non-TTTS twin pairs. Maternal levels of IGFs were comparable in the two groups. In the TTTS group, fetal birth weight gave a positive correlation with serum IGF-II levels (y = 0.25x + 361.1; r = 0.47; P < 0.05), and a negative association with IGFBP-1 levels (y = -0.72x + 1593.6; r = 0.58; P < 0.01). Our data argue against intertwin transfusion as the cause of intrauterine growth retardation in the donor twin and provide evidence that the placenta is the key regulator of the fetal IGF axis, especially when fetal genotype and maternal environments are similar.

Ontogeny of human fetal testicular apoptosis during first, second, and third trimesters of pregnancy.

During spermatogenesis in human adults, testicular germ cells proliferate, differentiate, and die by apoptosis. However, little is known about the temporal or spatial nature of this programmed cell death. Such information may be useful for understanding prenatal developmental biology as well as spermatogenesis during adulthood, particularly in the context of germ cell disorders. We undertook this study to determine 1) whether apoptosis occurred in a cell-specific fashion in the germ cell population and the supporting somatic cells; and 2) whether apoptosis varied with gestational age. We examined human fetal testicular tissues obtained from 17 karyotypically and structurally normal fetuses of mothers who underwent spontaneous or induced abortions. Three gestational ages were defined as follows: group A, 12-13 wk gestation (n = 5); group B, 20-22 wk gestation (n = 7); and group C, 37-40 wk gestation (n = 5). Morphology in conjunction with in situ end labeling was used to identify and quantify apoptotic nuclei in fetal gonadal tissues. The results of this study suggest that gonadal apoptosis occurred in germ cells, Sertoli cells, and Leydig cells at all gestational ages. Apoptotic death was highest in the Leydig cells, followed by germ cells and Sertoli cells. There was a significant positive correlation between the apoptosis of germ cells and Sertoli cells (P < 0.01) and a negative correlation between healthy germ cells and Sertoli cells (P < 0.001). There was also a negative correlation between the intratubular cell number and the gestational age. Specifically, the proportion of Sertoli cells decreased with gestational age, although there was no significant change in the germ cell in relation to gestational age. No such relationship was found in the Leydig cell population, all of which reside outside the seminiferous tubules. These results are the first to suggest that fetal testicular apoptosis begins in the first trimester, occurs in the three major cell types, and continues throughout pregnancy. Our data also suggest that in the fetal gonad, germ and Sertoli cell proliferation and death may be controlled by a genetic program distinct from that of the Leydig cells. This information is relevant to the understanding of abnormal spermatogenesis associated with infertility and to germ cell tumors in adult life.

Non-invasive method of evaluation of trophoblast invasion of spiral arteries in monochorionic twins with discordant birthweight.

To test the hypothesis that variation in birthweight between twin pairs is due to discordant placental development, we determined spiral arterial blood flow by colour pulsed Doppler ultrasound scan. We prospectively studied 24 twin pregnancies in the late second trimester with (n=12) and without (n=12) inter-pair difference in estimated birthweight of > or = 20 per cent. In the discordant growth group, there were seven cases with chronic twin-twin transfusion syndrome (TTTS) and five without. The blood flow in spiral artery of each twin's portion of the placenta was assessed by resistance index (RI) by colour flow pulsed Doppler within a 5 cm radius of cord insertion. In twins with discordant weight, RI was increased in the growth restricted (FGR) twin than the appropriate for gestational age (AGA) co-twin (0.46 +/- 0.02 vs 0.3 +/- 0.01; P< 0.001) and the control group (P< 0.001). However, delta RI was comparable between twins with and without TTTS (0.13 +/- 0.01 vs 0.19 +/- 0.02; P=NS). No such differences were found between concordant twin pairs (0.28 +/- 0.01 vs 0.29 +/- 0.1; P=NS) and AGA twins of the discordant growth group. This study indicates that growth restricted twins have increased resistance to blood flow in the spiral arteries than the AGA co-twins. This observation, therefore, suggests non-physiological remodelling of the maternal spiral arteries in response to migrating trophoblast in placental bed of FGR MC twins.

Atrial natriuretic peptide mediated polyuria: pathogenesis of polyhydramnios in the recipient twin of twin-twin transfusion syndrome.

We studied the role of atrial natriuretic peptide (ANP) in the pathophysiology of polyhydramnios in monochorionic (MC) twins with and without twin-twin transfusion syndrome (TTTS). Matched maternal, fetal blood samples and amniotic fluids (AF) were obtained in utero (n=12) and at birth (n=20) from MC twins with TTTS. Blood and amniotic fluid samples were also collected from non-TTTS MC twin pairs in utero (n=6) and at birth (n=20). In both groups cellular localization of ANP in the fetal kidney and heart was performed using anti ANP rabbit polyclonal antibody. Concentrations of ANP in pg/ml were determined by radioimmunoassay.In recipient fetuses, ANP levels were higher than the donors both in utero (P< 0.001) and at birth (P< 0.001). No such differences were found between the non-TTTS twins. In the TTTS group maternal ANP levels were lower than the non-TTTS group (P< 0.05). A linear relationship was found between fetal ANP levels and the AF volumes removed at fetal blood sampling (r(2)=0.68;P< 0.01, n=12). ANP was localized predominantly to the cytoplasm of the distal convoluted tubules of the fetal kidney and heart, and the intensity of immunostaining for ANP in kidney and heart were markedly greater in the recipient than the donor twin. No such differences were found between the twin pairs. These data suggest that polyhdramnios in the recipient twin occurs as a consequence of ANP mediated increase in fetal urine output and raises the possibility of direct fetal therapy with ANP blocking agents.

Discordant fetal leptin levels in monochorionic twins with chronic midtrimester twin-twin transfusion syndrome.

The objective of this study was to determine the plasma leptin concentrations in monochorionic twin fetuses with and without twin-twin transfusion syndrome (TTTS). Paired maternal and fetal blood samples were obtained at birth from monochorionic twin pregnancies complicated with (n=12) or without TTTS (n=12). Amniotic fluid samples were also collected from twin pairs at amnioreduction and/or fetal blood sampling in utero. Plasma and amniotic fluid leptin concentrations were measured by radio-immunoassay. Fetal leptin levels in the growth-restricted donor were lower than the recipient twin of the TTTS group (Delta mean 3.7; CI 2.6 to 4.7 ng/ml; P< 0.001). Fetal leptin levels were comparable between non-TTTS twin pairs (Delta mean 0.9; CI 0.1 to 1.4 ng/ml; P=0.10) and recipient twins of TTTS (P=NS). Maternal plasma concentrations of leptin were comparable between the two groups and were higher than the fetal levels. There was a positive association between cord leptin levels and birthweight of twin pairs (y=0.002x-0.37; r=0.58; P< 0.01; n=48). A significant positive relation was also found between delta leptin levels and percentage discordance in birthweight in the TTTS group (y=0.25x-2.21; r=0.82; P< 0.001, n=12). In conclusion, leptin levels in the recipient twins were three times higher than their growth restricted donor twins. However further studies are warranted to elucidate the underlying mechanism.

Prospective function of placental leptin at maternal-fetal interface.

Leptin is an endocrine and a growth factor which is important for regulation of body fat, feeding, and energy homeostasis. The anti-obesity function of leptin has been recently extended to reproduction, puberty and pregnancy as an endocrine signal to the hypothalamus. Leptin controls the functional integrity of the feto-placental unit thereby maintaining pregnancy by virtue of its immunomodulatory property via T lymphocytes or other proto-oncogenes. Dysregulation of autocrine/paracrine function of leptin at feto-placento-maternal interface may be implicated in the pathogenesis of recurrent miscarriage gestational diabetes, pre-eclampsia and intra-uterine fetal growth retardation including disturbance of fetal bone turnover. This review will focus on the role of leptin in normal and abnormal pregnancy and fetal growth.

Pharmacokinetics and pharmacodynamics of TRH during pregnancy.

OBJECTIVE: To determine the pharmacokinetics and pharmacodynamics of thyrotropin-releasing hormone (TRH) in pregnant women. METHODS: Twenty-four pregnant and eight nonpregnant women were given 400 micrograms TRH as either intravenous infusion or bolus. Serial venous samples were collected for TRH, TSH, thyroxine, and prolactin assay. RESULTS: When given as bolus, mean (+/- standard error of the mean) peak plasma concentration (50 +/- 5.2 and 73 +/- 5.1 ng/mL, P < .01), elimination half life (4.3 +/- 0.3 and 6.3 +/- 0.4 minutes, P < .001), and area under the curve (156.4 +/- 14.8 and 340.1 +/- 32.8 ng/mL/minute, P < .001) in pregnant subjects were reduced compared with controls, whereas plasma clearance (45.4 +/- 6.5 and 23.6 +/- 2.1 mL/kg/minute, P < .01) and volume of distribution (27.8 +/- 1.8 and 19.0 +/- 1.3% body weight, P < .01) were increased. When given by infusion, steady-state concentration (6.6 +/- 0.5 and 9.8 +/- 0.9 ng/mL, P < .01) and elimination half-life (4.6 +/- 0.5 and 6.3 +/- 0.3 minutes, P < .05) were lower in pregnant subjects than in controls. Thyrotropin-releasing hormone kinetics were independent of mode of administration. Although basal TSH and thyroid hormone concentrations were similar in patients and controls, the TSH response to TRH was blunted in pregnant subjects compared with controls (9.3 +/- 0.6 and 16.4 +/- 1.4 microIU/mL, P < .001). The basal (3187 +/- 488 and 147 +/- 16 mIU/L) and maximal prolactin response (6193 +/- 426 and 1316 +/- 106 mIU/L) were increased in pregnant subjects compared with controls (P < .001). CONCLUSION: The peak plasma concentration and elimination half-life of TRH are reduced during pregnancy because of the increased volume of distribution and rapid clearance. Mode of administration does not affect TRH pharmacokinetics, but the maternal pharmacodynamic response differs in patients receiving bolus compared with infusion.

Effect of antenatal administration of thyrotrophin releasing hormone on fetal flow velocity waveforms.

AIM: To determine whether antenatal administration of thyrotrophin releasing hormone (TRH), to promote lung maturation, alters blood flow through the fetal middle cerebral, umbilical artery, or ductus arteriosus and through the maternal uterine arteries. METHODS: The effect of transplacentally administered TRH on the fetal circulation was prospectively evaluated in 30 patients between 24 and 34 weeks' gestation. TRH (400 micrograms) was given to the mother intravenously either as a bolus or an infusion. Fetal effects were determined by measuring the maximum velocity and pulsatility index (PI) in middle cerebral artery, ductus arteriosus, uterine artery and umbilical artery Doppler waveforms. Measurements were made immediately before, and 10 and 60 minutes after maternal TRH administration. RESULTS: Intravenous injection of TRH had no significant effect on PI in the uterine, umbilical, or middle cerebral artery and the ductus arteriosus within 60 minutes of administration in either group. CONCLUSION: The antenatal use of TRH in conjunction with steroids for fetal lung maturity does not affect utero-placental or fetal haemodynamic variables, as measured by Doppler. These findings, therefore, do not support the suggestion that antenatal intravenous administration of TRH either as bolus or infusion may have immediate adverse vascular effects in the fetus.

Transfer of heparin across the human perfused placental lobule.

A system of dual perfusion of an isolated lobule of term human placenta was used as a model to study the transfer of heparin from maternal to foetal circulation. The metabolic viability of the system was assessed by measuring beta-HCG and alkaline phosphatase levels in both maternal and foetal perfusates. Creatinine and antipyrine were used as markers to determine juxtaposition of the maternal and foetal circulations. Results of this study indicate that following administration of a single bolus dose of heparin into the maternal circulation, its concentration declined slowly from 99.01 +/- 2.98 at 15 min to 97.23 +/- 4.12% and transfer of heparin in the foetal circulation was linear and increased from 0.10% +/- 0.05% at 15 min to 0.46 +/- 0.19% over a period of 120 min. The maternal (MAUC) and foetal (FAUC) concentration-time integrals were found to be 70160 +/- 1332 and 340 +/- 30 int. units min mL-1, respectively. Placental permeability of heparin and creatinine, calculated as the ratio of foetal concentration to the integral maternal-foetal concentration difference, was 8.65 x 10(-5) +/- 0.80 x 10(-5) and 0.033 +/- 0.006 mL min-1 g-1 of perfused placental weight, respectively. These data suggest that heparin was transferred from the maternal to the foetal circulation in small quantities.

Effect of the size of liposomes on the transfer and uptake of carboxyfluorescein by the perfused human term placenta.

The effect of the size of liposomes on the uptake and transfer of the low molecular-weight, hydrophilic and polar molecule carboxyfluorescein has been determined across the perfused human term placenta. Carboxyfluorescein-encapsulated neutral liposomes of three different sizes were prepared from equimolar concentrations of lecithin and cholesterol. Size distribution, encapsulation efficiency and stability of liposomes in blood-based media were determined. The concentration of carboxyfluorescein was measured spectrophotometrically. The transplacental transfer and placental uptake of free carboxyfluorescein (control data) were respectively 1.9 +/- 0.2 and 5.0 +/- 0.7% of initial dose. The placental uptake and foetal concentration of carboxyfluorescein were significantly increased by small liposomes (P < 0.05), and reduced by large (0.82 +/- 0.13%; P < 0.05) and multilamellar liposomes (0.32 +/- 0.11%). There was a negative correlation between liposome size and transplacental transfer (y = -0.53 + 0.9x; r = 0.96; P < 0.001; n = 24) and placental uptake of carboxyfluorescein (y = -5.9 + 6.5x; r = 0.84; P < 0.001; n = 24). The study indicates that placental uptake and transfer rate of liposomal carboxyfluorescein were dependant upon the size of liposomes.

Differential binding of warfarin to maternal, foetal and non-pregnant sera and its clinical implications.

The object of this study was to determine whether differential binding of sodium warfarin in paired maternal and cord sera accounts for its adverse effects on the foetus. In-vitro binding of sodium warfarin to human serum albumin in maternal, foetal, and non-pregnant (control) subjects was determined by equilibrium dialysis at 37 degrees C. Our data suggest that at therapeutic concentrations, sodium warfarin has a single high affinity binding site on human serum albumin with an association constant of 1.65 x 10(-3) M. Serum albumin concentration in the control sera (4.42 +/- 0.08 g dL-1) was comparable with that in the cord sera (4.54 +/- 0.26 g dL-1) but was significantly higher (P < 0.01) than the maternal levels (4.03 +/- 0.21 g dL-1). Binding data indicate that the fraction of unbound warfarin in the foetal sera (6.8 +/- 1.9 g dL-1) was significantly higher than in the maternal (3.60 +/- 1.3 g dL-1; P < 0.01) and non-pregnant sera (1.96 +/- 0.6 g dL-1; P < 0.001). The maternal and foetal fractions of free warfarin were directly proportional to the concentrations of free fatty acids (y = 1268 - 110x; r = 0.93; P < 0.001), and bilirubin (y = 8.7 + 1.4x; r = 0.91; P < 0.001), respectively. This study indicates that warfarin was more strongly bound in the maternal sera than in the foetal sera; this was probably because of the competitive and allosteric effect of free fatty acid and bilirubin in the maternal and foetal sera, respectively. The clinical significance of this observation is discussed in this paper.

The role of nitro-reduction and nitric oxide in the toxicity of chloramphenicol.

Recent work on the toxicology of chloramphenicol suggests that its propensity to cause damage to the blood forming organs may be related to its potential for nitro-reduction and the subsequent production of nitric oxide. In this study both aerobic and anaerobic nitro-reduction of chloramphenicol by human foetal and neonatal liver results in the production of the amine derivative. However intermediates of the reaction nitroso- or glutathionesulphinamido-chloramphenicol could not be detected by hplc. Perfusion of chloramphenicol through isolated lobules of human placentae caused a decrease in blood pressure at a time which coincided with a peak of nitric oxide production. However, although the pressure drop could be reversed by an inhibitor of nitric oxide synthetase, the nitric oxide profile remained the same. These observations suggest that involvement of the para-nitro group of chloramphenicol could cause both hemotoxicity and hypotension in susceptible individuals.

Effect of lipid composition of cationic SUV liposomes on materno-fetal transfer of warfarin across the perfused human term placenta.

INTRODUCTION: Use of drugs that cross the placenta freely are currently avoided during pregnancy. We investigated whether cationic small unilamellar (SUV) liposomes of different lipid compositions could prevent the transfer and uptake of warfarin across human term placenta. METHODS: Cationic liposomes encapsulated warfarin was prepared by using lecithin (F-SUV) or sterylamine (S-SUV) with cholesterol and stearylamine. The size distribution, encapsulation efficiency, and stability were determined in blood-based media. The transfer kinetics of free and liposomally encapsulated warfarin were studied in a dually perfused isolated lobule of human term placenta with creatinine. Concentrations of warfarin were measured by fluorimetry. Data are expressed as % of initial dose added and given as mean ± sd. RESULTS: Warfarin crossed the placenta freely (14.9 ± 1.1%). Trans placental transfer of warfarin was significantly reduced by F-SUV (6.4 ± 0.6%; P < 0.001) and S-SUV liposomes (5.0 ± 0.8%; P < 0.001). Placental uptake of F-SUV (6.3 ± 1.7%; P < 0.001) was greater than that of S-SUV liposomes (2.2 ± 0.5%; P < 0.001). CONCLUSION: Our data suggest that cationic liposomes reduce trans placental transfer of warfarin. If confirmed "in vivo", liposomes might provide an alternative non-invasive method of drug delivery to the mother.

Leptin and bone turnover in monochorionic twins complicated by twin-twin transfusion syndrome.

INTRODUCTION: To test the hypothesis that the bone metabolism of a growth-restricted foetus is regulated by genetic, placental and/or foetal factors through leptin, we investigated the foetal bone turnover in monochorionic pregnancies complicated with or without twin-twin transfusion syndrome (TTTS). METHODS: Maternal and cord bloods were collected from gestational-age-matched monochorionic twins with (n=15) and without (n=15) TTTS. The samples were assayed for leptin, cross-linked carboxyl terminal telo-peptide (ICTP, a marker of bone resorption) and pro-peptide (PICP, a marker of bone formation) of type I collagen by radioimmunoassay (RIA). RESULTS: In the growth-restricted donor twin, the plasma concentration of leptin (P < 0.001), PICP (P < 0.001) was lower, while that of ICTP (P < 0.001) was higher than the recipient twin of the TTTS group. In contrast, leptin, PICP and ICTP were comparable in non-TTTS twins. In the recipient twin of TTTS and non-TTTS twins, leptin was positively associated with PICP (r=0.73; n=45, P < 0.001) and negatively with ICTP (r=-0.68; n=45; P < 0.001). No such association was found between leptin and bone marker in the growth-restricted donor twin of the TTTS group. CONCLUSION: Our data suggest that, in AGA twins, leptin maintains bone metabolism by inhibiting resorption and enhancing bone formation. In contrast, growth-restricted donor twins have high bone turnover and this does not seem to be due to leptin deficiency.

Abundant vascular anastomoses in monoamniotic versus diamniotic monochorionic placentas.

OBJECTIVE: The study's aim was to compare the vascular anatomy of monoamniotic with uncomplicated diamniotic monochorionic pregnancies. STUDY DESIGN: The fetoplacental circulations of both twins in 18 monochorionic placentas were perfused after delivery under optimal physiologic conditions, and anastomoses were delineated by dye-contrast injection. Six were from pregnancies with monochorionic monoamniotic twins and 12 from uncomplicated monochorionic diamniotic twin pregnancies. RESULTS: The cord insertions in monochorionic monoamniotic placentas were central, with a median intercord distance of 3.2 cm (range 1.7 to 6.9 cm), whereas in monochorionic diamniotic control placentas the cord insertions (n = 24) were rarely central (marginal, 13; velamentous, 2) or eccentric (6), with a mean intercord distance of 9.6 cm (5.2 to 16.7; P < .001). Cord entanglement was present in 5 of 6 cases of monochorionic monoamniotic placentas and in none of the monochorionic diamniotic placentas. Monochorionic monoamniotic placentas had more anastomoses than did monochorionic diamniotic placentas, both overall (median 13 vs 5 respectively, P < .01) and for each of the different types (arterioarterial, venovenous, and arteriovenous, P < .01). CONCLUSIONS: Monoamniotic monochorionic placentas have significantly greater numbers of both superficial and deep anastomoses than do uncomplicated monochorionic diamniotic pregnancies. This observation suggests a vascular basis for the extreme rarity of twin-twin transfusion syndrome in monoamniotic pregnancies.