Dogs have a gestation period of 59-65 days, with an average of 63 days. Earlier than 59 days and the puppies may be premature and underweight and could die, later than 65 days and the puppies may be postmature and require veterinary attention.
2 to 3 days before the mother is due, take her rectal temperature each morning. 12-18 hours before labor begins, her temperature will drop from a normal 101.3F to 99.5F or below. But, don't assume a normal temperature in the 101-102 range means she won't deliver soon, as occasionally this temperature drop doesn't occur. 12-24 hours before whelping occurs, the mother loses her appetite, becomes more active and restless, and may dig in the garden or in the house. This would be the time to restrict her to her whelping area. Dogs tend to give birth late at night or early in the morning. Make sure to offer her water and to take her outside every few hours in case she has to go to the bathroom. And always have a 24-hour veterinarian close by in case anything goes wrong!