I'm assuming that you are asking a ? lollypop and if you are, the answer is maybe
in regards to platys and the gravid spot.
I will try to clarify this issue of the Gravid Spot if I may, as it is often asked about. I think it basically comes down to this...All livebearers (talking about Guppies, Swordtails, Mollies and Platysí here) may have a gravid spot to a certain extent. Certainly Guppies do and it is particularly pronounced because of their colouring and transparency of their skin. It can show in the other livebearers to varying degrees, OR not at all...and for the same reason, it may be hidden by the fishís natural colouring and their skin isnít as transparent as that of guppies.
Some livebearers may seem to have a gravid spot constantly, even if they arenít holding fry and it may just mean that they are mature and have mated at some stage, also some livebearers have a naturally darkened area just above the anal fin. The best sign of pregnancy is that they start getting larger and rounder in the abdomen.
I personally donít think you can count on the size of the gravid spot as an indication of when the female will drop fry. It can be one indication certainly, as once the eggs are fertilized, the gravid spot (if showing) usually increases in size as the fry develop (many say it is a myth that the gravid spot is actually the eyes of the fry showing through...I really donít know)! but the best telltale sign that birth is imminent is usually when her stomach looks like it will burst and starts to get a square box shape to it, because all livebearers will have this look about them whether they have a gravid spot or not. It is hard to say exactly when she will drop fry, as it is up to her in the end.
I know I included info. that you didn't even ask about, but hope it helps some!