Weird kanji and furigana combination in h-doujin

While reading h-doujin in Japanese, I found certain kanji combinations that replace the commonly used – mostly for vulgar words. Here are a few examples (the bolded ones are the weird ones):

**身精**ちゃいそうです
**で**ちゃいそうです

**身精**そうです
**イキ**そうです

**子宮**に**身精**して
**ナカ**に**ダ**して

What’s the deal with these kanji combinations? To abide by certain Japanese laws for printing or publication?

by AzAcc31