Failure to up-regulate VEGF165b in maternal plasma is a first trimester predictive marker for pre-eclampsia

Pre-eclampsia is a pregnancy-related condition characterized by hypertension, proteinuria and endothelial dysfunction. VEGF(165)b, formed by alternative splicing of VEGF (vascular endothelial growth factor) pre-mRNA, inhibits VEGF(165)-mediated vasodilation and angiogenesis, but has not been quantified in pregnancy. ELISAs were used to measure means+/-S.E.M. plasma VEGF(165)b, sEng (soluble endoglin) and sFlt-1 (soluble fms-like tyrosine kinase-1). At 12 weeks of gestation, the plasma VEGF(165)b concentration was significantly up-regulated in plasma from women who maintained normal blood pressure throughout their pregnancy (normotensive group, 4.90+/-1.6 ng/ml; P<0.01, as determined using a Mann-Whitney U test) compared with non-pregnant women (0.40+/-0.22 ng/ml). In contrast, in patients who later developed pre-eclampsia, VEGF(165)b levels were lower than in the normotensive group (0.467+/-0.209 ng/ml), but were no greater than non-pregnant women. At term, plasma VEGF(165)b concentrations were greater than normal in both pre-eclamptic (3.75+/-2.24 ng/ml) and normotensive (10.58 ng/ml+/-3.74 ng/ml; P>0.1 compared with pre-eclampsia) pregnancies. Patients with a lower than median plasma VEGF(165)b at 12 weeks had elevated sFlt-1 and sEng pre-delivery. Concentrations of sFlt-1 (1.20+/-0.07 and 1.27+/-0.18 ng/ml) and sEng (4.4+/-0.18 and 4.1+/-0.5 ng/ml) were similar at 12 weeks of gestation in the normotensive and pre-eclamptic groups respectively. Plasma VEGF(165)b levels were elevated in pregnancy, but this increase is delayed in women that subsequently develop pre-eclampsia. In conclusion, low VEGF(165)b may therefore be a clinically useful first trimester plasma marker for increased risk of pre-eclampsia.     

Placental anticoagulant protein-I: measurement in extracellular fluids and cells of the hemostatic system

Placental anticoagulant protein-I (PAP-I), a member of the lipocortin protein family, is a potent in vitro anticoagulant whose in vivo function is unknown. Very low levels of PAP-I were present in plasma of normal volunteers (0 to 5 ng/ml) and in randomly chosen plasma specimens from hospitalized patients (0 to 28 ng/ml). Review of selected hospital records did not reveal any single clinical entity that correlated with plasma levels. PAP-I was also found in amniotic fluid (12 to 107 ng/ml) and in conditioned medium of cultured endothelial cells (49 +/- 20 ng/ml). Gel filtration experiments showed that PAP-I was intact and uncomplexed in plasma and amniotic fluid. The protein was fairly abundant intracellularly: 4080 +/- 2560 ng/mg total protein in cultured umbilical vein endothelial cells; 178 +/- 109 ng/mg in platelets; 564 +/- 384 ng/mg in leukocytes; and 8.4 +/- 4.3 ng/mg in erythrocytes. The levels of PAP-I increased in platelet-rich plasma after stimulation of platelets with arachidonic acid but not after stimulation with ADP, epinephrine, thrombin, ristocetin, or collagen. These data suggest that PAP-I probably does not function as a circulating natural anticoagulant in normal persons.     

Pharmacokinetics and transplacental passage of imipenem during pregnancy.

Imipenem pharmacokinetics were studied in early pregnancy (n = 7; length of gestation, 8.6 +/- 1.5 weeks, mean +/- standard deviation), in late pregnancy (n = 7; length of gestation, 38.7 +/- 1.4 weeks), and in the nonpregnant state (n = 6). A single dose of 500 mg of imipenem-cilastatin (1:1) was administered as a 20-min infusion. Multiple plasma and urine samples, as well as specimens of umbilical plasma and amniotic fluid from the pregnant subjects, were collected at frequent intervals for 8 h. Imipenem concentrations were assayed by specific microbiologic assay. The mean peak concentrations in plasma were 14.7 +/- 4.9, 14.9 +/- 5.2, and 43 +/- 28.3 micrograms/ml in early pregnancy, late pregnancy, and the nonpregnant state, respectively. The volumes of distribution were significantly larger during early pregnancy (0.98 +/- 0.45 liter/kg of body weight, P < 0.005) and late pregnancy (0.59 +/- 0.19 liter/kg, P < 0.05) than in the nonpregnant state (0.33 +/- 0.10 liter/kg), and total clearances from plasma were faster in early pregnancy (12.7 +/- 7.8 ml min-1 kg-1, P < 0.05) and late pregnancy (10.7 +/- 4.6 ml min-1 kg-1, P < 0.05) than in the nonpregnant state (5.77 +/- 1.19 ml min-1 kg-1). The mean concentrations in amniotic fluid were 0.07 +/- 0.01 and 0.72 +/- 0.85 micrograms/ml in early and late pregnancy. The mean umbilical venous and arterial drug concentrations were 1.72 +/- 1.22 and 1.64 +/- 1.22 micrograms/ml. The feto-maternal ratio at the time of cesarean section was 0.33 +/- 0.12. These results indicate that an adjustment of doses of imipenem may be required when treating pregnant women because of considerable changes in imipenem pharmacokinetics during pregnancy.     

Immunoassay for the determination of surfactant apoprotein (SP-A) in human amniotic fluid: comparison with other indices of assessing foetal lung maturity.

The concentration of the major surfactant-associated protein SP-A (28-36 kDa) was determined in 73 amniotic fluid samples obtained from normal (n = 40) and complicated (n = 33) pregnancies. Lecithin/sphingomyelin (L/S) ratio and phosphatidylglycerol (PG) levels were also determined in all the samples by one-dimensional step-wise thin-layer chromatography. An enzyme-linked immunosorbent assay was used to determine human lung surfactant apoprotein SP-A. The amount of SP-A in human amniotic fluid increased as a function of gestational age from 8 mg l-1 at 36 weeks to 11.75 mg l-1 at 40-41 weeks of gestation. There was a significant difference (p less than 0.01) in amniotic fluid SP-A concentration from female (9.93 +/- 0.60 micrograms ml-1) compared to male (9.10 +/- 0.52 micrograms ml-1) foetuses. In amniotic fluid samples obtained from a group of complicated pregnancies, SP-A levels were significantly lower than in the normal group when adjusted for gestational age and sex of the foetus (p less than 0.05).     

Plasma Aldosterone Concentration at Delivery and during the Newborn Period

Aldosterone concentrations in plasma of women on normal sodium intake undergoing cesarean section were 3.7+/-1.4 ng/100 ml (mean+/-1 SD). These values were significantly lower (P < 0.001) than those observed in mothers on normal sodium diet, delivered by the vaginal route (14.9+/-7.0 ng/100 ml). A significant elevation (P < 0.001) of the concentrations was found if the mothers had been on sodium restriction and/or diuretics (44.9+/-24.2 ng/100 ml). In supine position, adult nonpregnant subjects have aldosterone concentrations in plasma of 1.7+/-1.4 ng/100 ml on normal sodium intake and of 16.7+/-8.1 ng/100 ml on low sodium diet.Simultaneous determinations of aldosterone levels in cord blood showed that cord values were significantly higher than those of the corresponding mother (P < 0.01 by paired t test). However, values in cord blood of infants born to mothers on a normal sodium intake were significantly lower (P < 0.005) than those of infants whose mothers had required low sodium diet and/or diuretics during their pregnancy.Aldosterone concentrations in plasma of infants 1-72 hr of age and born to mothers on normal sodium intake were 25.9+/-11.7 ng/100 ml (mean +/-1 SD). These values were significantly lower (P < 0.005) than those of infants born to mothers on restricted sodium intake with or without diuretics (80.3+/-54.4 ng/100 ml). The concentrations at birth were not significantly different from those observed during the first 3 days of life (P > 0.6).     

Amniotic fluid phospholipids and foetal lung maturation

An analysis was made of samples of amniotic fluid from 82 pregnant women with normal pregnancies, ranging from 29 to 40 weeks of amenorrhoea. Lipid extraction was quantitative and individual phospholipids were isolated by two-dimensional chromatography. The lecithin/sphingomyelin ratio (L/S) increased significantly (t = 2.17; p less than 0.05) between 35 and 36 weeks of amenorrhoea (from 2.9 +/- 1.0 to 4.3 +/- 1.7). Phosphatidyl-glycerol (PG) was detected from 35 weeks of pregnancy, the time at which the incidence of amniotic samples with mature surfactant (L/S greater than or equal to 2.7 and presence of PG) was 9%; mature surfactant incidence increased to 55.5% at 36 weeks and 100% at 37 or more weeks. There was a good correlation between surfactant levels in amniotic fluid and new-born respiratory function.     

Angiotensin I-converting enzyme in amniotic fluid

Angiotensin I-converting enzyme (ACE) is present in human amniotic fluid. We characterized the enzyme by both its antigenic and enzymatic properties. Using a specific direct radioimmunoassay, ACE was quantified and characterized in each of the 19 samples tested. Mean level was 136 +/- 83 ng/ml. Amniotic ACE completely crossreacted, like that in plasma and kidney, with antibodies raised against the lung enzyme. ACE activity in amniotic fluid averaged 8.7 +/- 5.6 microU/ml using Hip-His-Leu as substrate and was significantly correlated with ACE antigen levels. ACE was not associated with the cells or the free intracellular organelles in amniotic fluid, and the enzyme was present in soluble form. Angiotensinase activity and high levels of kininase activity were found in amniotic fluid. Inhibition studies with captopril and anti-human ACE antibodies suggest that angiotensinases and kininases other than ACE were also present. Because renin, mostly in inactive form, and angiotensinogen were also found in these amniotic fluids, it appears that a complete, although not fully activated, renin angiotensin system is present in amniotic fluid and fetal membranes during pregnancy.     

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.     

Measurement, Characterization, and Source of Somatostatin-like Immunoreactivity in Human Amniotic Fluid

Somatostatin-like immunoreactivity (SLI) is widely distributed in tissues and biological fluids. To determine whether SLI is also present in amniotic fluid, samples obtained by amniocentesis from 30 normal and 27 abnormal pregnancies were studied by radioimmunoassay. Direct incubation of [(125)I-Tyr(1)]tetradecapeptide somatostatin (SRIF) with amniotic fluid resulted in 89% tracer degradation. Damage was reduced to <5% when samples were acidified and boiled before the assay. With this technique, SLI was detectable in all normal amniotic fluid samples; the mean level at 15-20 wk of gestation (320+/-55 pg/ml, n = 15) being 4.5 times higher than the mean at 32-43 wk (70+/-12 pg/ml, n = 15) (P < 0.001). In cases of preeclampsia (n = 6), gestational diabetes (n = 5), anencephaly (n = 1), and meningomyelocele (n = 1), SLI values were in the normal range, but in one juvenile diabetic and one patient with chronic renal failure, SLI was undetectable (<10 pg/ml). In a pair of monochorionic diamniotic twins, SLI levels were very different (33 and 197 pg/ml), which suggests that fetal factors are more important than materno-placental ones in determining amniotic fluid SLI. Serial dilutions of amniotic fluid showed parallelism with standard SRIF. When concentrates of pooled amniotic fluid were chromatographed on Sephadex G-25 columns, all SLI eluted in the void volume ahead of SRIF even after treatment with 8 M urea and dithiothreitol. This "big" SLI incubated in amniotic fluid showed 100% stability over 24 h at 37 degrees C, whereas SRIF was rapidly inactivated (t((1/2)) congruent with 7 min). Extracts of placenta and fetal membranes contained no SLI, but small amounts (6-20% of total amniotic fluid SLI) were found in cells from fresh fluid. Radioimmunoassay of SLI in extracts of seven paired cord arterial and venous plasma samples showed no arteriovenous gradient consistent with fetal origin of cord blood SLI. It is concluded that (a) amniotic fluid contains SLI which is of fetal origin and (b) normal levels vary with gestational age. The SLI has a higher molecular weight (>/=5,000) and is more stable in amniotic fluid than SRIF.     

Early oxidative stress in amniotic fluid of pregnancies with Down syndrome

OBJECTIVE: Some evidence suggests that oxidative stress, due to an imbalance between oxidants and antioxidants, occurs in babies with Down syndrome (DS). This study tests the hypothesis that oxidative stress occurs early in DS pregnancies. DESIGN AND METHODS: Isoprostanes (IPs), a new marker of free radical-catalyzed lipid peroxidation, were measured in amniotic fluid from pregnancies with normal, growth restricted and DS fetuses, diagnosed by karyotype analysis of amniotic cells cultured. RESULTS: A nine-fold increase in IP concentrations was found in amniotic fluid of pregnancies with DS fetuses. This increase (595.15; 542.96-631.64 pg/ml, median; 95% CI), was greater than in pregnancies with fetal growth-restricted fetuses (155; 130.57-172.23 pg/ml, median; 95% CI) and normal fetuses (67; 49.82-98.38 pg/ml, median; 95% CI; p<0.0001). CONCLUSIONS: The study reveals that oxidative stress occurs early in pregnancy and supports the idea of testing whether prenatal antioxidant therapy may prevent or delay the onset of oxidative stress diseases in the DS population.     

Serum histidine-rich glycoprotein during pregnancy and hormone treatment

The concentration of serum histidine-rich glycoprotein (HRG) was determined by radial immunodiffusion during weeks 27-42 of pregnancy in 110 pregnant women. HRG was also measured in serum from 11 lactating women 6 weeks post partum, from 11 women taking oral contraceptives, and from four women having progestin-releasing subcutaneous capsules used for contraception. The concentration of serum HRG decreased during the last trimester of pregnancy reaching a nadir at the 36-37th week (HRG 49 +/- 14 g/l, mean +/- SD). Thereafter serum HRG increased slightly towards term. In pregnancies complicated by hypertension the concentration of HRG was lower than in normal pregnancies at 32 weeks of pregnancy, but in other pathological pregnancies the values fell within the normal range. By 6 weeks postpartum normal non-pregnant HRG levels had been reached (107 +/- 13 g/l). The concentration of serum HRG was significantly lower in oral contraceptive users (74 +/- 22 g/l) than in controls (109 +/- 25 g/l, P less than 0.005). Low dose progestin treatment had no effect on serum HRG. The results show that serum HRG decreases during pregnancy and with oral contraceptive treatment and suggest that oestrogens are responsible for this increase.     

Peripheral metabolism of insulin, proinsulin, and C-peptide in the pregnant rat.

To clarify alterations in carbohydrate metabolism which occur in pregnancy, metabolic clearance rates of insulin, proinsulin, and C-peptide were measured by the constant infusion technique in term-pregnant rats and in virgin littermates. In addition, placental permeability to these peptides was evaluated by simultaneous determination of their concentration in fetal blood, amniotic fluid, and maternal arterial blood and the renal extraction and excretion of insulin and C-peptide were determined during simultaneous studies of renal hemodynamics. The metabolic clearance rate (MCR) of insulin was higher (P less than 0.005) in pregnant animals (61.5+/-1.7 ml/min per kg nonconceptus body weight) than in virgin littermates (51.5+/-2.2 ml/min per kg). Insulin disappearance from the circulation after both single injection and discontinuance of a constant infusion was also faster in gravid animals. In contrast, the MCR of proinsulin and C-peptide, and the disappearance of C-peptide from the circulation were similar in pregnant and control rats. The placenta was virtually impermeable to each of the three polypeptides since their mean levels in both fetal blood and amniotic fluid did not exceed 2.5 ng/ml and were only minimally influenced by pharmacological concentrations as high as 60 ng/ml in the maternal circulation. The renal clearance of insulin (renal arteriovenous insulin difference X renal plasma flow) was lower, and its contribution to insulin MCR was less in pregnant animals than in controls (19.4+/-1.5% vs. 28.7+/-3.7%, P less than 0.05), whereas the renal clearance and renal clearance/MCR of C-peptide were similar in pregnant rats and virgin littermates. These results indicate that the peripheral metabolism of insulin is accelerated in pregnancy, while that of pro-insulin and C-peptide is unaffected. Since transplacental passage of insulin is negligible and its renal clearance is not increased, the enhanced MCR of insulin in pregnancy is due to increased metabolism at an extrarenal site probably within the placenta itself.     

Comparison of amino acid concentrations in amniotic fluid from fetal neural tube defective and normal pregnancies

Amniotic fluid collected during the second trimester of pregnancy was analysed for amino acid and protein concentrations. The composition of amniotic fluid from pregnancies complicated by fetal anencephaly or spina bifida was investigated for variance from normal amniotic fluid. In spina bifida the hydroxy amino acids were raised whilst the branched chain amino acids were lower in concentration. In anencephaly the total amino acid and the protein concentrations were raised, and a wider range of concentrations for most of the amino acids was apparent.     

Maternal serums and amniotic fluid levels of human placental lactogen in gestational diabetes.

Human placental lactogen (hPL) levels were measured radioimmunologically in maternal serum and in amniotic fluid between the 37th and 39th weeks of gestation in sixteen gestational diabetic and thirty normal pregnant women. There was no significant difference in maternal serum hPL levels between diabetic (6.1 microgram/ml) and normal pregnant women (6.4 microgram/ml). In contrast, the diabetic group was found to have significantly (P less than 0.001) higher concentrations of amniotic fluid hPL (1.2 microgram/ml) than normal pregnant women (0.8 microgram/ml).     

Maternal serum and amniotic fluid levels of human placental lactogen in gestational diabetes

Abstract. Human placental lactogen (hPL) levels were measured radioimmunologically in maternal serum and in amniotic fluid between the 37th and 39th weeks of gestation in sixteen gestational diabetic and thirty normal pregnant women. There was no significant difference in maternal serum hPL levels between diabetic (6.1 μ g/ml) and normal pregnant women (6.4 μ g/ml). In contrast, the diabetic group was found to have significantly ( P< 0.001) higher concentrations of amniotic fluid hPL (1.2 μ g/ml) than normal pregnant women (0.8 μ g/ml).     

Amniotic fluid interleukin 6 in preterm labor. Association with infection.

To evaluate whether IL-6 participates in the host response to intrauterine infection, we studied IL-6 bioactivity and isoforms in amniotic fluid (AF). Two different assays for IL-6 were used: the hepatocyte stimulating factor assay (in Hep3B2 cells) and the SDS-PAGE/immunoblot assay. IL-6 determinations were performed in 205 AF samples. Samples were obtained from patients in the midtrimester of pregnancy (n = 25), at term with no labor (n = 31), at term in active labor (n = 40), and from patients in preterm labor (n = 109). Higher AF IL-6 levels were observed in women in preterm labor with intraamniotic infection than in women in preterm labor without intraamniotic infection (median = 375 ng/ml, range = 30-5000 ng/ml vs. median = 1.5 ng/ml, range = 0-500, respectively, P less than 0.0001). The 23-25- and 28-30-kD IL-6 species could be readily detected in SDS-PAGE immunoblots performed directly on 10-microliters aliquots of AF from patients with intraamniotic infection. Among women in preterm labor with culture-negative AF, those who failed to respond to subsequent tocolytic treatment had higher AF IL-6 concentrations than those who responded to therapy (median = 50 ng/ml vs. median = 1.2 ng/ml, respectively, P less than 0.05). Only low levels of IL-6 were detected in AF obtained from normal women in the midtrimester and third trimester of pregnancy. Decidual tissue explants obtained from the placentas of women undergoing elective cesarean section at term without labor (n = 11) produced IL-6 in response to bacterial endotoxin. In a pilot study, AF IL-6 was determined in 56 consecutive women admitted with preterm labor. All patients (n = 10) with elevated AF IL-6 (cutoff = 46 ng/ml) delivered a premature neonate. 4 of these 10 patients had positive AF cultures for microorganisms. These studies implicate IL-6 in the host response to intrauterine infection and suggest that evaluation of AF IL-6 levels may have diagnostic and prognostic value in the management of women in preterm labor.     

Maternal and fetal atrial natriuretic peptide levels, maternal plasma renin activity, angiotensin II, prostacyclin and thromboxane A2 levels in normal and preeclamptic pregnancies.

To clarify the possible role of elevated atrial natriuretic peptide (ANP) in the pathophysiology of preeclampsia, we measured ANP, renin activity (PRA), angiotensin II (Ang II), TXB2 (a stable metabolite of TXA2) and 6-keto-PGF1 alpha (a stable end product of PGI2) concentrations in the plasma of 19 normal pregnant women and 35 severe preeclamptic patients at term. Plasma ANP levels in the preeclamptic patients (n = 35, 71.5 +/- 3.8 pg/ml, mean +/- S.E.) and also umbilical plasma ANP (n = 35, 83.0 +/- 4.2 pg/ml) were significantly (p less than 0.01) higher than those of normal pregnant women plasma (n = 19, 58.7 +/- 3.7 pg/ml) and umbilical plasma (n = 19, 47.6 +/- 4.7 pg/ml). There was a significant (p less than 0.01) positive correlation between maternal ANP levels and fetal ANP levels (n = 54, r = 0.44). Plasma PRA and 6-keto-PGF1 alpha levels in preeclampsia were significantly (p less than 0.05) lower than those of normal pregnancy. The ratio of 6-keto-PGF1 alpha/TXB2 in preeclampsia was significantly (p less than 0.01) lower than that of normal pregnancy as we reported previously. There was no significant correlation between plasma ANP level and plasma PRA, Ang II, plasma TXB2 and 6-keto-PGF1 alpha concentrations. Moreover there was no significant correlation between plasma ANP level and the severity of preeclampsia. These data suggest the possibility of a transplacental crossing of ANP secreted by feto-placental unit, which might be, at least in part, responsible for the high ANP levels observed in preeclampsia. The ANP in preeclampsia is not related directly to hypertension, but it may play a substantial role in the regulation or normalization of blood volume and vascular reactivity.     

Human beta-endorphin and beta-lipotropin levels in maternal and fetal plasma and amniotic fluid

We measured beta-endorphin (beta-EP) and beta-lipotropin (beta-LPH) levels in human maternal and fetal plasma and amniotic fluid, simultaneously. It appeared evident that maternal circulating levels of beta-EP (n = 11, 163.9 +/- 12.9 pg/ml, mean +/- S.E.) and beta-LPH (n = 11, 413.0 +/- 25.9 pg/ml) at delivery were significantly (p less than 0.01) higher than those of maternal plasma at term (beta-EP; n = 4, 18.3 +/- 2.1 pg/ml, beta-LPH; 213.4 +/- 24.3 pg/ml) and those of amniotic fluid (beta-EP; n = 5, 8.5 +/- 1.2 pg/ml, beta-LPH; 215.1 +/- 44.9 pg/ml). Fetal beta-EP levels (n = 11, 79.1 +/- 5.8 pg/ml) were significantly (p less than 0.01) higher than those of amniotic fluid. These data suggest that the origin of amniotic fluid beta-EP may be an increased synthesis in the maternal and fetal pituitary gland but not in the placenta.     

Acetylcholinesterase and butyrylcholinesterase measurement in the pre-natal detection of neural tube defects and other fetal malformations

Acetylcholinesterase activity in amniotic fluid was measured at 30 degree C by a reaction rate method employing acetyl-beta-methyl thiocholine as substrate and ethopropazine as a selective inhibitor of butyrylcholinesterase. This assay proved more specific than previously reported methods. Activity was greater in five cases of anencephaly (4.8-9.7 U/l) and nine cases of spinal bifida (5.1-8.6 U/l) than in 50 pregnancies with normal outcome (mean activity 2.0 +/- 0.9 (S.D.) U/l). There was no overlap between results from normal and neural-tube-defect groups, and the results showed no significant correlation with gestational age. Butyrylcholinesterase activity in amniotic fluid was measured using butyrylthiocholine as substrate. In accordance with previous reports, levels were elevated in pregnancies affected by neural tube defects. The ratio butyrylcholinesterase/acetylcholinesterase activity showed similar values for anencephalic, spina bifida and normal pregnancies; however, the two cases of exomphalos investigated could be clearly distinguished from all other groups on this basis.     

Plasma volume contraction: a significant factor in both pregnancy-associated hypertension (pre-eclampsia) and chronic hypertension in pregnancy

The role of plasma volume in hypertension in pregnancy (pre-eclampsia) was investigated. Significant volume expansion from non-pregnant levels (16.5 +/- 1.60 ml/cm height) was present throughout pregnancy in 189 normal women, reaching 23.1 +/- 1.21 ml/cm at 33-36 weeks amenorrhoea. In another 40 initially normotensive pregnant women who developed hypertension, similar early volume expansion was followed by significant volume contraction in the third trimester, before evaluation of blood pressure in 29 (20.6 +/- 1.26 ml/cm), after it in 11 (18.6 +/- 1.27 ml/cm). Equivalent volume contraction was present in another 44 women studied only after hypertension developed in the third trimester. Oedema had no value as a clinical sign. In another 30 women with chronic hypertension, blood pressure was inversely related to plasma volume (r = 0.822) and to fetal growth (r = -0.710), which was directly related to plasma volume (r = 0.701). Plasma volume depletion plays a significant role in hypertension in pregnancy.