Dogs have a pre-heat that last 7 days, then they have the bleeding, about another seven days,then the third seven days they are most likely to conceive puppies. A puppy conceived on the third day of that wk will be a little less developed when she whelps (delivers her litter). The last puppy to be conceived can easily be as healthy as the others that are a couple of days older. Since gestatation time is 58-63 days, even the last egg to be fertilized has a great chance. The key to any healthy puppy is what the mom dog eats while pg. A good quality food is crucial.
Also, the female is not receptive to the male after that third seven day period. She will even bite to prevent him from entering her.
A date finder that helps calculate the gestation dates for dogs, cats, rabbits, etc can be gotten free by phoning 800-786-4751. Also by going to
www.revivalanimal.com
Yorkie babies are the best thing ever! Enjoy!
Rizzi