If pregnant in multiple wombs (or anal womb) and all births are due during an event, only one pregnancy comes to term--all others just disappear. I think this is true of all events but I'm certain it is true while traveling between starship ports. I've observed this with bothrioc eggs (preg in 3 wombs and ass) and Seigewulf Bimbo Dom eggs (preg 3 wombs and ass).