They are ovoviviparous, but examination in controlled captivity has shown the very soft egg-like membrane around the young is discarded immediately on birth.
Family Poeciliidae – livebearers and relatives (some oviparous, some ovoviviparous)
Those aquatics snakes are ovoviviparous, the incubation lasts 5 in 6 months and the female expels from 6 to 17 youngs.