Regulatory response to washout of amniotic fluid in sheep

Qin Yang, L. Davis, A. Hohimer, J. Faber, D. Anderson

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


To test the hypothesis that a substance present in the amniotic fluid could serve as a regulator of amniotic fluid volume, we drained and discarded amniotic fluid while replacing it with lactated Ringer solution that was isotonic to amniotic fluid. Seven ewes with singleton fetuses at 119 ± 1 days of gestation (mean ± SE) were instrumented with multiple indwelling catheters in the pedal artery, pedal vein, and amniotic cavity. During the exchange periods, an average of 3,019 ± 171 ml/day of lactated Ringer solution was infused into the amniotic cavity while an equal amount of amniotic fluid was pumped out and discarded. During the control period, amniotic fluid composition and volume were not altered. Exchange and control periods started with the same amniotic fluid volume, lasted 3 or 4 days, and were randomized with regard to order. Amniotic fluid volume measured by vacuum drainage was 556 ± 98 ml at the end of the control period and 986 ± 209 ml (P = 0.03) at the end of the exchange period. Fetal arterial blood gases, hemodynamic parameters and the osmolality gradient between fetal plasma and amniotic fluid were not altered by the exchange process. A linear relationship between the control amniotic fluid volume and the volume at the end of the exchange period (P = 0.003) suggests that the animals with larger control volumes responded to isovolumic dilution with a larger volume increase. We conclude that amniotic fluid may contain a substance that regulates amniotic volume.

Original languageEnglish (US)
Pages (from-to)H1339-H1343
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Issue number3 57-3
StatePublished - Mar 2005


  • Chorion
  • Fetal
  • Intramembranous absorption
  • Isovolumic exchange
  • Volume

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)


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