The pig people are already giggling at this reference, but if you're not a person who has hung or looked at a lot of sow cards in your life, let me explain. You may wonder how in the world on farms with lots of animals (several of the farms I work with typically have between 2000-3000 sows (mamas) on the farm at any one time), farmers are able to keep track of which sows are due to farrow (have babies) when. Well, that is where computers and ear tags and an organizational system come in handy. Each sow is kept with a group within the barn, that corresponds to the week she was bred, and therefore, everyone in the group will all have babies at approximately the same time. (Let's just say that pigs are a little more predictable than people - as I am now +5 days past my due date!)
Each sow has a card hung above her stall that records all her vital information (like the computer that it seems like 4 people log on to to ask me the same 5 questions every week for the last month at my OB appointments), and then when she gets moved to the farrowing house, she gets a new card that is ready to record all the information from the new litter of pigs: when they were born, how many were born, were any transferred to another litter, as well as all of her past history: how many litters has she had? how many pigs did she have in each litter? did she have any previous problems that those assisting need to be aware of? It's really pretty similar to people. Each sow is monitored every 15 minutes during farrowing to make sure that things are progressing smoothly, and they are assisted when necessary.
Sows are kept with their babies for ~3 weeks at which time the piglets are weaned from the sow and moved to another farm, where they start a diet based mainly on corn and soybean meal, as well as other vitamins & minerals. The pig's gut changes at this time to be ready for the new diet. This may seem early, but a pig will naturally wean itself by ~5 weeks anyway, and the ~3 week time frame is an optimum for both sow and piglets for their future health.
My "group" is fairly large with few slots available in the "farrowing room" right now, so we continue in a holding pattern until Baby Pollard decides to make their debut!