Can the sex of a baby change in pregnancy?
The Simple answer is NO, the sex of a baby is determined at conception! When either an XY (Boy) sperm or a XX (Girl) sperm won the race
here is a link to read about development if sex organs
Image credit https://www.sciencealert.com/scientists-identified-elusive-molecule-helps-sperm-find-eggs-marine-calcium-chemoattractant-chemotaxis