The birth of puppies is the culmination of a process that begins two months earlier, when a male dog mates with a female dog. Once a female dog's eggs are fertilized, the gestational period lasts approximately 60 days. Generally, a female dog's pregnancy may not become apparent until the fifth week of gestation. At the fifth week, the female dog's mammary glands swell and darken as they begin to fill up with milk. The dog's abdomen may also have expanded slightly, giving a slight indication that the puppies are growing in size.
By the sixth or seventh week of pregnancy, the female dog's abdomen appears noticeably larger and it is usually apparent by this time that she is pregnant. In addition, she may show the need to urinate more frequently. By the eighth week of pregnancy, a milky discharge may emanate from her nipples as her milk production increases and her body prepares for birth. At the time of birth, about 60 percent of puppies are positioned in the uterus to come out head-first; the other 40 percent come out feet-first. Puppies that are positioned in other ways may have a difficult time emerging and may not survive without an expert breeder or veterinarian's intervention. An expert breeder or veterinarian may try to change the position of the puppy by gently using his fingers.
However, generally very little human intervention is needed when a female dog gives birth. A newborn puppy will emerge in a placental membrane, and while this membrane needs to be removed before the puppy can breathe, the female dog will usually remove this with her mouth on her own. She will also sever the umbilical cord with her teeth and lick the puppy to stimulate his breathing. If the female dog fails to do this on her own, then human intervention is necessary to help the newborn puppy breathe. The placental sac must be removed near the puppy's head as there is only a short window of time before the oxygen supply in the sac is depleted and the puppy suffocates. Mucus and fluids should be removed from the puppy's mouth, and he should be rubbed with a towel to stimulate his breathing. The umbilical cord can also be tied with unwaxed dental floss and then cut 2 inches away from the abdomen. Wipe iodine on the cut end of the umbilical cord to prevent infection. After the puppies are breathing on their own, the female will encourage them to suckle on her teats. Her milk is important, not only for their nutrition, but also so they ingest colostrum. Colostrum is a milk-like substance that contains antibodies to strengthen the puppies' immune systems. Once the puppies are breathing and suckling properly on their own, the birthing process is complete.