Coffin birth - Kannaibunben

...As the decay progresses further, the body becomes giant-like due to the decomposition gases, and the corpse that was submerged at the bottom of the water rises to the surface, and in the case of a pregnant woman's corpse, the uterus inverts and prolapses due to the increase in intraperitoneal pressure, and the fetus is delivered. This phenomenon is called a coffin birth. This decay phenomenon is equivalent to one week in air for two weeks in water and eight weeks in soil, and this law is called Kaspar's Law.

*Some of the terminology that refers to "coffin delivery" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…さらに腐敗が進行すると，腐敗ガスのため巨人様化し，水底に沈んでいた死体は浮上し，妊娠女性死体では腹腔内圧の上昇により子宮が反転脱出して胎児が娩出される。この現象を棺内分娩という。この腐敗現象は，空気中1週間の腐敗は水中2週間，土中8週間に相当し，この法則を〈カスパーの法則〉という。…

※「棺内分娩」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報