Pregnancy in pigs lasts for 3 months 3 weeks and 3 days. A well-fed sow will produce at least 10 piglets (litter) from each pregnancy and may have 2 litters each year.
If the sow shows no sign of being in heat 3 weeks after mating she is pregnant. The pregnancy will last about 3 months 3 weeks and 3 days. During the pregnancy, the sow will need plenty of feed high in nutrients and will especially need more feed towards the end of the pregnancy. She should be given some feed high in nutrients e.g. grain and green stuffs every day. Giving the sow access to clean soil or grass with roots from land where no pigs have been kept will allow her to get the minerals she needs. Give the sow plenty of clean bedding when birth is close.
The sow becomes restless and starts to make a nest within 24 hours of giving birth. The teat will produce milk when gently squeezed.
Blood stained fluid may be passed from the vagina 1 to 2 hours before birth begins and if small greenish pellets appear the first piglet will appear within an hour.
Gently rubbing the udder will make the sow relax and lie on her side in the position to give birth.
Farrowing is a natural process and the sow will usually need no help. Once the first piglet is born the others, and the afterbirth, will quickly follow. Farrowing should be completed within 2 to 3 hours. The navel cord will break (you do not need to cut it) and the piglet will immediately search for a teat and milk. If the navel bleeds, tie it tightly with a clean string or cord.
If the sow shows all the signs of farrowing but she has not produced a piglet and is pawing with a hind leg, or if 45 minutes has passed since the first piglet appeared and there is no sign of the second you will have to help the sow.
Clear the piglet's mouth and nose of mucous and if it is not breathing you can slap it to encourage it to breath. Gently rub the piglet dry and put its mouth on a teat.
Source : Pashu Sakhi Handbook