Abstract
The author has intended to study how varies the frequency of onset of labor when a frontal line passes. For this purpose, he has applied Masuyama's spatial nmethod.
Among all parturitions at San-ikukai Hospital (Tokyo) in 1952-53, 3527 cases have been investigated, where onsets of labor were spontaneous and durations of pregnancy were over 36 weeks. The frequency of onset of labor was calculated, whereby seasonal and diurnal errors were eliminated.
The result is as follows: when a depression passes near Japan, the frequency of onset of labor shows a significant variation, namely, it increases before a cold frontal line passes (containing the case where a warm frontal line approaches or passes) and decreases after it passes. These influences are confirmed within the range of 24 hours before or after the passage of cold frontal line respectively (in terms of distance, within 1000km before or behind the cold frontal line).
At last, he has discussed the cause of this phenomenon in connection with autonomic nerves and posterior pituitary gland hormones.
