How Long does the Pregnancy Last

Before I mentioned an average 63 days. However, it's convenient to add that this is very variable, depending on, for example, if the bitch is a first-timer, a big sized dog, the size of the litter, the age of the bitch and her physical conditions. All these things have to be taken into count without forgetting that the moment of fertilization of the ovules as this might have been significantly delayed by anything that might have happened in the moment of mating. Don't forget that, in perfect conditions, spermatozoids have a lifespan of about seven or eight days once inside the vagina and uterus.

Of course if we consider that the first day of pregnancy was in the moment that diestrus begins then you can calculate that it lasts approximately 57 days, with an 85% of females that become pregnant only hours after mating. It is for this reason that it's extraordinary useful for the owners of female dogs to perform vaginal cytologies during the first days of heat, in order to precisely calculate when the first day of diestrus will take place, thus you will be able to have a better idea of when she will give birth.