Oxytocin given in a pulsatile manner to the ewe at 120 to 140 days' gestational age increases fetal sheep plasma cortisol

Drew W. Sadowsky, Juliann Martel, Theresa Cabalum, M. Gabriella Poore, Peter W. Nathanielsz

Research output: Contribution to journalArticle

8 Scopus citations

Abstract

A single intravenous injection of oxytocin into pregnant sheep (123 to 144 days' gestational age) causes a bout of myometrial activity and an increase in fetal plasma corticotropin levels. We hypothesized that a sustained increased frequency of myometrial contractures accelerates the normal increase in fetal adrenal secretion in sheep in the last 3 weeks of gestation. To test this hypothesis, pulses of saline solution (group 1, 9 ewes and 10 fetuses) or oxytocin (group 2, 11 ewes and 12 fetuses) 600 or 960 μU/kg/min for 5 of every 30 minutes were infused into the maternal jugular vein for 6 days beginning at day 128 ± 2 (mean ± SD) days' gestational age. Total myometrial activity increased to 160% of baseline in group 2 by day 6. Myometrial activity did not change throughout the study in group 1. Maternal plasma cortisol concentrations did not rise during oxytocin infusion when compared with their own baselines (group 2) and were not different from concentrations in saline-infused ewes (group 1). By day 4 of oxytocin administration fetal plasma cortisol concentrations had risen significantly above baseline in group 2 (p < 0.05). Fetal plasma cortisol concentrations did not rise in group 1. Corticotropin levels were not elevated in the fetal carotid arterial plasma of either group. A small but significant decrease occurred in fetal carotid arterial Po2 in group 2 by day 6 but not in group 1. In conclusion, increased myometrial activity produced by pulsed oxytocin is accompanied by increased fetal plasma cortisol concentrations, demonstrating that long-term alteration of myometrial activity affects fetal adrenal function over several days at this critical period of gestation.

Original languageEnglish (US)
Pages (from-to)200-205
Number of pages6
JournalAmerican Journal of Obstetrics and Gynecology
Volume166
Issue number1 PART 1
DOIs
StatePublished - Jan 1992
Externally publishedYes

Keywords

  • fetal cortisol
  • fetal sheep
  • myometrial contractility
  • oxytocin
  • Pulsatile infusion

ASJC Scopus subject areas

  • Obstetrics and Gynecology

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