Females spend most of their pregnancy feeding in the northern waters off Greenland, only returning south in the fall to give birth to a new pup exactly one year later.
  Once they have arrived at the whelping patch on the southern pack ice, females give birth to a single pup. The birth occurs quickly, often taking less than one minute. Pups are usually born hind flippers first.
While giving birth, the mother harp seal quickly spins around to sniff her pup, nose to nose. During this first contact, the mother learns the unique odour of her pup, which she will use to identify it each time she returns to feed it. A female harp seal will only feed her own pup, and nursing is almost always preceded by the female nosing the pup to confirm its identity. This sniffing of the pup prior to feeding is often described as a harp seal "kiss."

It is extremely important that initial contacts between a mother and pup not be disturbed. If the female is forced to leave the ice before a bond has been formed with her pup, she may not recognize it upon returning to the ice. An abandoned pup will starve to death.

The mother harp seal rarely feeds while she is nursing, and must support both herself and her pup using the energy stored in her blubber. Females may lose over 3 kg (6.5 lbs) a day during lactation and, by the time she leaves her pup, the mother will have lost more than one quarter of her total body weight.