Ay naku, hindi ako nakaranas nyan directly pero may kaibigan akong nangyari na ganyan after swimming, turned out she had a minor nose bleed from the cold water contracting her blood vessels, which is actually pretty common lalo na pag mabigat ang flow ng tubig sa ilong. Pero since you're seeing pinkish blood after maligo, better to have your OB check it out para sure lang, especially if ito recurring or may slight pain pa, kasi maraming reasons pwede yan from something minor to something na kailangan i-monitor during pregnancy. Mag-DTap ka na lang soon pang safe.