A reader asked me about the phrase alive and kicking, and said she'd heard that it related to pregnancy. In the first volume of their 7-volume dictionary Slang and Its Analogues Past and Present, published in 1890, Farmer and Henley say that "the allusion is to a child in the womb after quickening". Quickening is "the first perceptible movements of the fetus during pregnancy" (OED). This dictionary defines alive and kicking as "an intensive form of alive in the most colloquial sense of being alert and full of action". Farmer (the sole editor of Volume 1) then goes on to say "In the days of Pierce Egan's Tom and Jerry, alive partook far more of the nature of slang than now". Pierce Egan was an early 19th-century journalist, whose well-known and well-loved characters Corinthian Tom and Jerry Hawthorn rambled and caroused their way around London, entertaining readers with their witty descriptions of the characters they met from all walks of life (see this page from the British Library for more information on Egan's Tom and Jerry).
The OED does not allude to pregnancy in its definition of alive and kicking. It merely says "indubitably alive; very lively and active". Eric Partridge's Dictionary of Historical Slang says something similar. In Cassell's Dictionary of Slang, Jonathon Green says the expression is often used as a response to a speaker who assumes that a third party is dead (No, he's still alive and kicking).