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THE ROLE OF THE FETUS IN THE FORMATION OF AMNIOTIC FLUID
Author(s) -
Lind T.,
Kendall Anne,
Hytten F. E.
Publication year - 1972
Publication title -
bjog: an international journal of obstetrics and gynaecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.157
H-Index - 164
eISSN - 1471-0528
pISSN - 1470-0328
DOI - 10.1111/j.1471-0528.1972.tb15799.x
Subject(s) - fetus , amniotic fluid , sodium , hysterotomy , endocrinology , amnion , vasopressin , chemistry , medicine , pregnancy , biology , genetics , organic chemistry
Summary One hundred and thirty‐one conceptuses obtained at hysterotomy between 12 and 22 weeks were examined to establish the relation between amniotic fluid volume and fetal weight, and between the sodium and urea content of amniotic fluid and that of maternal and fetal plasma. In 37 of the fetuses bladder urine was obtained for the estimation of sodium and urea. In 44, samples of abdominal skin were obtained and the movement of sodium and water through it was studied in an Ussing‐type cell; ion movement across the amnion and chorion was also measured. Up to mid‐pregnancy amniotic fluid volume was closely related to fetal weight, and the sodium and urea content of amniotic fluid volume was closely related to fetal weight, and the sodium and urea content of amniotic fluid was more closely related to that in fetal plasma than to that in maternal plasma. Data showing that the fetal kidney is capable of reabsorbing sodium and concentrating urea even before mid‐pregnancy is presented. Intermittent addition of fetal urine may explain why the sodium content of amniotic fluid is slightly below that of plasma. Fetal skin was shown to be freely permeable to sodium and water in early pregnancy but the rate of diffusion slowed as mid‐pregnancy was reached with evidence of a block at the external skin surface. No electrical potentials were detected and neither vasopressin nor angiotensin affected the rate of diffusion. Fetal membranes, at least in the experimental conditions used, were also freely permeable to sodium and water. The evidence supports the hypothesis that, in the first half of pregnancy, amniotic fluid may be an extension of the fetal extracellular fluid space.