By John W. Reynolds (auth.), J. H. P. Jonxis M.D., H. K. A. Visser M.D., J. A. Troelstra M.D. (eds.)
The notion of the foeto-placental unit as an built-in endocrine organ has been outlined lately by means of many in vivo stories on the seventeenth- twentieth week of gestation. A functioning foeto-placental unit is important for many of the elevated oestrogen creation of being pregnant and for the supply of glucocorticoids and aldosterone to the foetus. Neither the foetus nor the placenta on my own have the required enzyme structures for the synthesis of those teams of steroids. notwithstanding, whilst the foetus and placenta functionality as a unit, the entire enzyme structures are current for the synthesis of those steroids from circulating ldl cholesterol. The placenta, yet no longer the mid-gestation foetal adrenal, can synthesize physiologically a great deal of pregnenolone from circulating ldl cholesterol. a part of the pregnenolone is switched over to progesterone within the placenta through the 3~-HSD procedure (absent within the foetus). The progesterone is transferred to the foetus the place it truly is reworked by means of C-II, C-17, C-18 and C-21 hydroxylases (all absent within the placenta) to cortisol, corticosterone and aldosterone. Pregnenolone transferred from the placenta to the foetus undergoes 171X-hydroxylation, aspect chain splitting and sulfurylation (absent within the placenta) and is switched over to DHAS. The DHAS may possibly suffer 161X-hydroxylation (absent within the placenta) within the foetal liver and be transported to the placenta as 161X-OH-DHAS. There it really is subjected to a impartial steroid sulfatase (absent within the foetus) and is switched over to oestriol through motion of the 3~-HSD procedure and the aromatizing enzyme system.
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Extra resources for Aspects of Praematurity and Dysmaturity: Groningen 10–12 May 1967
Transplacental passage of androgens from the mother is one of the dangers for the foetus. Would you like to comment on this? The third question is, is there another steroid which provides a better indication of foetal distress than oestriol. For instance this 15-hydroxylated compound, it might give a much more accurate indication than oestriol for the obstetrician. Dr. Reynolds: I cannot give you any experimental evidence that cortisol and aldosterone are essential for the functioning of the midterm foetus.
1. Diagram showing the relationship of growth potential (heavy, diagonal line) and growth support coming from the mother via the placenta (dotted areas) of the fetus. Actual growth after limitation by growth support is shown by thin lines. In the foregoing it was assumed that the fetal growth potential is about the same in all pregnancies, but there are certain exceptions to this, apart from the sex difference in fetal body weight which is unexplained as far as its mechanism is concerned. The incidence of growth retardation among malformed fetuses is very high.
This makes it impossible to differentiate between infants of 37-39 weeks of gestational age, and those of 40 weeks or more. 's were unclassified, being either incomplete, without waking or sleeping patterns, or too pathological. There were four errors of classification. G. findings in a special series of 13 infants (below the 10th percentile) have been recorded on days 3, 7, 14, 21, during waking, drowsiness, sleep and arousal, in combination with metabolic studies. We missed the sleep tracing once (at day 3) and the waking tracing twelve times.