On average, a Rottweiler's pregnancy lasts for 63 days.From the time of conception, most canines stay pregnant for 56 to 66 days.

Rottweiler pregnancy is very unnoticeable for the first few weeks after conception, according to WebMD. The only sign that the Rottweiler is pregnant may be slight weight gain. By the 40th day, however, the signs become more apparent, as the nipples enlarge and darken in color. As time passes, the female may begin leaking or expressing milk or fluid from her nipples as she prepares for birth. During the last few weeks of pregnancy, the belly enlarges greatly and movement of the pups can be felt.