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In domestic dogs, sexual maturity (puberty) occurs between the ages of 6 to 12 months for both males and females, although this can be delayed until up to two years of age for some large breeds. Pregnancy is possible as soon as the first estrus cycle, but breeding is not recommended prior to the second cycle.
Most dogs whelp approximately 63 days after breeding (normal range of 58 to 71 days). It can be helpful to start taking your dog's rectal temperature with a glass-bulb thermometer from about 55 days after breeding. Make sure it is inside the anus and ideally against the wall of the rectum.