C. H. Rodeck

Effect of Gestational Age on Fetal and Intervillous Blood Gas and Acid-Base Values in Human Pregnancy

Intervillous, umbilical venous and umbilical arterial blood samples were obtained by cordocentesis or fetoscopically from 200 pregnancies at 16-38 weeks gestation. The fetuses were either not affected by the condition under investigation or it was one which would not affect blood gas and acid-base status. Blood pH, pO2, pCO2, bicarbonate, base excess and plasma lactate concentration were determined and ranges for each parameter are presented. Samples obtained fetoscopically were more acidotic, hypercapnic and had a greater base deficit than those obtained by cordocentesis. In the umbilical venous samples, the pO2 decreased, while the bicarbonate, base excess and lactate increased with gestation. In the umbilical arterial samples the pO2 decreased and pCO2 increased; there were no other significant changes with gestation. Similarly, in the intervillous samples the only significant change with gestation was that of a decrease in pO2.

FETOSCOPY GUIDED BY REAL‐TIME ULTRASOUND FOR PURE FETAL BLOOD SAMPLES, FETAL SKIN SAMPLES, AND EXAMINATION OF THE FETUS IN UTERO

Techniques for sampling pure fetal blood, fetal skin and for fetal examination by fetoscopy are described in detail after experience gained in 151 diagnostic fetoscopies on 145 patients. Of particular importance were a real‐time scanner and a particle size analyser. The region of insertion of the umbilical cord into the placenta was the optimum site for obtaining pure fetal blood, and this was achieved in 136 out of 143 patients (95 per cent) sampled at 18 to 23 weeks gestation. This made maternal blood transfusion before prenatal diagnosis of haemoglobinopathies unnecessary. An anterior placenta rarely prevented successful fetoscopy, and often made fetal blood sampling easier. Four fetal losses (3·7 per cent) were judged to be due to fetoscopy.

Real time pelvic ultrasonography during the periovulatory period of patients attending an artificial insemination clinic

Real time ultrasonography was used to examine the ovaries of 50 patients at the calculated time for artificial insemination with donor semen (AID). Forty-two (84%) had one or more follicles greater than 13 mm in diameter. Both ovaries were monitored daily until the main follicle had ruptured (mean number of examinations, 2.4 per patient; range, 1 to 5). Seven women became pregnant (mean follicular diameter, 21.6 mm; range, 18 to 25 mm). The fecundability rate was 12%, compared with 6% for a corresponding group of 50 patients who were not examined with ultrasound. Seven patients experienced mittelschmerz, and in 39 the leading follicle had ruptured before the rise in basal body temperature (BBT). Ultrasonography may be used to confirm the presence or absence of preovulatory follicle prior to treatment.

False positive gel-acetylcholinesterase results in blood-stained amniotic fluids

Summary. The effect of blood contamination on the gel‐acetylcholinesterase (AChE) test used in the diagnosis of fetal open neural‐tube defects was studied with amniotic fluid samples artificially contaminated with fetal or maternal blood in concentrations covering a range exceeding that usually found in clinical practice. Amniotic fluid samples contaminated with maternal blood gave negative gel‐AChE results at all concentrations. Contamination with fetal blood yielded positive results if the erythrocyte concentration was greater than about 60 × 106 cells/ml. Thus contamination of amniotic fluid with blood is only likely to cause false positive gel‐AChE results if this critical concentration is exceeded. Such samples will occur only rarely in clinical practice but when they do the diagnosis should be made with caution.

The effect of replacing fetal hemoglobin with adult hemoglobin on blood gas and acid-base parameters in human fetuses

In order to determine whether the differences between fetal and adult hemoglobins are important to fetal oxygenation, pH, PO2, PCO2, bicarbonate, and base excess were measured in umbilical venous and arterial blood samples obtained from fetuses with erythroblastosis fetalis. The values from fetuses that had previously been transfused and had predominantly adult hemoglobins were compared with those that had not been transfused and had predominantly fetal hemoglobin. Umbilical arterial blood was more acidotic and had a greater base deficit, while the umbilical venous PO2 was 4.8 mm Hg higher in the samples with adult hemoglobins than in those with fetal hemoglobin. The results suggest that oxygenation of fetal tissue is better with fetal hemoglobin but that adult hemoglobin can be compensated by an increase in oxygen transfer.

STUDY OF THE UTERINE CAVITY BY ULTRASOUND IN THE EARLY PUERPERIUM

The uterine cavity length, maximum width and area were determined by ultrasonic scanning in ten women after their first full term delivery (primiparae) and ten women after their second full term delivery (secundiparae) during the first eight days of the puerperium. A consistent and progressive decrease in all three measurements was found; although faster between days 1 and 3 than between days 3 and 8 the difference was statistically significant only for cavity area. The rates of involution for both parity groups were similar and were not influenced by breast feeding. The cavity length in primiparae and secundiparae was also similar, but the maximum width on days 3, 5 and 8 and the area on days 3 and 5 were significantly greater in secundiparae. A correlation between the infant birth weight and cavity length on day 1 and between infant birth weight and cavity area on days 1, 3 and 5 was found in secundiparae.

Complement factors in fetal and maternal blood and amniotic fluid during the second trimester of normal pregnancy

Summary. Complement factors (C3, C4, C5; Factors B, H and I) were measured in maternal and fetal serum and amniotic fluid obtained from 55 women with singleton pregnancy undergoing diagnostic fetoscopy at 15 to 28 weeks gestation. Maternal serum levels were consistently 10 times higher than fetal levels which in turn were 10 times higher than levels in amniotic fluid. Spearman rank correlation analysis at weeks 20 to 22 (n= 20) revealed a statistically significant correlation between maternal and fetal levels of C3 and Factors B and I, and between maternal and amniotic fluid levels of Factors B and I. A significant increase in fetal levels of C3, C4 and Factor H, and in amniotic fluid levels of C3 and Factor B was seen in relation to advancing gestational age. These differences were not seen in maternal scrum during the short interval of pregnancy studied. These data confirm earlier assumptions of fetal synthesis of complement factors, and provide normal reference ranges of complement factors in fetal blood and amniotic fluid.

Prenatal diagnosis of hereditary red cell membrane defect

Summary The red cells of a severely anaemic 2‐year‐old child of a white British family showed high haemolytic fragility with poikilocytosis. The cells showed markedly impaired thermal stability. The mother was phenotypically normal, but the fathers red cells showed mild elliptocytosis. The spectrin from the latter, extracted at low temperature, was 30% dimeric (cf. 5–10% in normals). Tryptic digests of the spectrin from both father and daughter showed a reduction in the fragment of 80 000 molecular weight, derived from the terminus of the α‐chain, and the elevation of a fragment of molecular weight 46 000, as well as one of 53 000. These characteristics and the autosomal recessive inheritance lead to a diagnosis of type II hereditary pyropoikilocytosis, so far reported only in two black American families (Lawler et al, 1983). The spectrin from the father was examined with respect to thermal conformational stability, and was found to be normal. The spectrin from the cells of the daughter gave evidence of the presence of oxidative (disulphide) cross‐links, as well as of extensive noncovalent aggregation. Blood was obtained from the umbilical cord vein of the 19‐week fetus of the pregnant mother: 250 μl of blood was used for preparation of red cell membranes for SDS‐gel electrophoresis and for extraction of spectrin. Analysis of the spectrin by gel electrophoresis in the native state revealed that the proportion of dimer was within the normal range, and the fetus therefore did not possess the hereditary pyropoikilocytosis phenotype. It is suggested that the procedures described could be generally applied to the prenatal identification of phenotypes associated with severe haemolytic anaemias.

Transplacental arteriovenous gradients for glucose, insulin, glucagon and placental lactogen during normoglycaemia in human pregnancy at term

The potential contributions of placental extraction and degradation to glucoregulatory hormone turnover in late pregnancy were assessed by measuring arteriovenous differences for glucose, insulin, glucagon and human placental lactogen (hPL) across the uterine and fetal circulation in ten pregnant women at the time of elective caesarean section. The observations were made during stable conditions of euglycaemia; values for maternal arterial glucose, insulin, glucagon and hPL were 78.8 +/- 5.0 mg/dl, 10.1 +/- 2.1 microU/ml, 72.0 +/- 8.5 pg/ml and 5.18 +/- 0.59 micrograms/ml, respectively. The glucose decrements observed consistently across the uterus and fetus indicated uptake by the placenta and fetus, and in the maternal circulation the arterial-uterine vein increment for hPL was 2.10 +/- 0.44 micrograms/ml. However, within the limits of analytical accuracy, no significant gradient could be demonstrated for insulin across the uterine (maternal) or umbilical (fetal) circulations. A small (8.5 per cent) but significant arteriovenous difference for glucagon was observed across the uterus but none was found on the fetal side of the placenta. The findings indicate that detectable gradients for insulin cannot be demonstrated under basal conditions of metabolism and at normal rates of placental blood flow. The results do not exclude the possibility of more significant extraction ratios under other physiological conditions or at higher concentrations of glucoregulatory hormones.

Normal levels of ATP, total nucleotides and activities of three enzymes related to nucleotide metabolism in fetal erythrocytes

Pure fetal blood was obtained by direct‐vision fetoscopy from 30 fetuses at 17–23 weeks gestation. The erythrocyte concentrations of ATP and total nucleotides and the activities of the enzymes pyrimidine‐5′‐nucleotide nucleosidase (Fyr5N), phosphoribosylpyrophosphate (PRPP) synthetase and adenylate kinase (AK) were analysed by established techniques to find the normal ranges for this gestational age. The ranges were relatively narrow and could serve as reference values for the prenatal diagnosis of defects in nucleotide metabolism.