妊 (Kanji for pregnant)

Onyomi

NIN	Pregnant NINjas can't hide so good.

They say you gotta treat a pregnant woman like a king.

妊娠(にんしん) する	pregnant ★★★☆☆ 妊 (pregnant) + 娠 (pregnancy) = 妊娠 (pregnant)
妊婦(にんぷ)	pregnant woman ★★☆☆☆ 妊 (pregnant) + 婦 (housewife / lady) = 妊婦 (pregnant woman)
避妊(ひにん)	birth control ☆☆☆☆☆ 避 (avoid / dodge) + 妊 (pregnant) = 避妊 (birth control)

	Meaning	Hint	Radical
姓	family name	BORN	生
妊	pregnant	KING	王

The person BORN to a woman takes her family name, but the pregnant woman is like the KING who rules her baby.