Like already been mentioned by me a couple of times, there are also females that won't show a gravid spot. What's going on when a female doesn't show a gravid spot? It means that at the spot where usually the gravid spot appears, there is a dense concentration of chromatophores (color cells) in all three skin layers. Which makes that spot not translucent. So, no gravid spot will be seen. A progressing pregnancy won't change anything.