健康・医療情報学ジャーナル

Uterine Contractions in Normal Labor Developed by a Positive Feed-back and Oscillation

Abstract

Kazuo Maeda*

Aim: To clarify the developing mechanism of regular uterine contractions in the labor.
Methods: The similarity of normal regular labor contractions of the uterus to the electrical oscillation was studied.
The electrical oscillation technique was adapted to regular labor contraction of the uterus, where innervations between
the uterus and brain were reported in animals in four papers.
Results: Interval between peaks of contractions was 2 min and the amniotic pressure was 40 mmHg in typical labor
contractions. Labor contractions were repeated from the onset of labor until the delivery of fetus. Attachment of reverse
contraction curve to normal contraction curves formed sine wave-like repetition, similar closely to electrical oscillation
waves. A positive feed-back was estimated from the uterus to the amplifying input
Comments: A biological amplifier is the hypothalamic center-hypophysis-oxitocin secretion, its output is uterine
labor contraction, and its positive feed-back loop to the amplifier input is the innervations between the uterus and
hypothalamus, of which presence was reported in animals. The biological positive feed-back loop produces oscillationlike
regular uterine contractions, of which wave length is 2 min, frequency 0.008 Hz and amplitude 40 mmHg.
Conclusion: Regular stable labor contractions of uterus is formed in the oscillation by the positive feed-back system
composed of hypothalamus-hypophysis-oxitocin secretion, uterine contractions and uterus-brain innervations.