Research Article
Kazuo Maeda*
Abstract
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.