The gestation period of a Molly is 24-48 days and is usually dependent upon the temperature of the water. First broods are small of about 15 offspring. Broods increase in number with each successive brood to number up to 150 per brood as the female grows larger. The larger the female, the larger the number of young ones that she will have born. She will have a dark mark in the front of her anal fin. This is called the gravid spot and it becomes quite noticeable as she approaches giving birth, mollies which are about to spawn will seem almost square from the back view and will be very swollen in the middle.
