A sow or gilt carries piglets for about 114 days, famously remembered as 3 months, 3 weeks, and 3 days, with a normal range of 112 to 116 days. This pig pregnancy week by week timeline compresses the whole 16 week gestation into one chart: what the piglets are doing at each stage, what to do about feed and housing, and when to have the farrowing pen ready.
Enter the breeding or service date in the pig gestation calculator for exact dates, or use the farrowing calculator to plan the farrowing window and countdown.
Not sure she is bred? This page is the full 114 day timeline. If you are still deciding whether the service took, start with how to tell if a pig is pregnant for confirmation methods, then come back for the week by week plan.
The 114 Days at a Glance
Days 1 to 30
Quiet, no signs
Days 30 to 60
Belly growth
Days 60 to 90
Mammary development
Days 90 to 114
Udder, milk, farrowing
Pig Pregnancy Timeline Chart
Four phases, one table. Print it for the farrowing barn and pencil in your own dates once the calculator gives you the due date.
| Stage | Days | What Happens | What To Do |
|---|---|---|---|
| Month 1Weeks 1 to 4 | Days 1 to 30 | Fertilized eggs implant in the uterus by roughly day 14. The sow stays quiet, eats normally, and shows no outward change worth noticing. | Record the service date and circle day 114 on the calendar. Feed a normal gestation ration and skip the extra helpings: fat gilts and sows farrow worse. An unbred sow returns to heat 18 to 21 days after service, so a missed return is your first sign. |
| Month 2Weeks 5 to 8 | Days 30 to 60 | Piglet organs are formed and the litter count is set. The belly starts to grow in this month, easiest to see from behind as the sow walks away from you. | Confirm the pregnancy by ultrasound from about day 21 to 30 if you did not catch the missed heat. Keep housing stable with no new pen mates and no fighting, and feed to hold body condition rather than gain it. |
| Month 3Weeks 9 to 13 | Days 60 to 90 | Piglets grow fast and the sow's belly is obviously round. Mammary tissue develops through this stretch and the nipples begin to stand out along the underline. | Raise feed gradually as her appetite climbs, keep water flowing, and leave her group and housing alone. Skip transport and far apart moves in this window; late pregnancy stress costs you at farrowing. |
| Final MonthWeeks 13 to 16 | Days 90 to 114 | The udder fills and tightens, milk arrives in the final days, the vulva swells and reddens, and nesting behavior starts 12 to 48 hours before farrowing. | Stock the farrowing kit by day 105. Move her to the crate or pen around day 110 so she settles in, warm the area for newborn piglets, and start checking for milk, nesting, and restlessness twice a day. |
Day counts run from the breeding or service date. Averages assume 114 days; plan for piglets any time from day 112 to 116, with gilts often running a day or two shorter than mature sows.
The Final Two Weeks: What to Watch
From day 100, look at the underline twice a day. The udder fills steadily, then in the last day or two goes from plump to strutting, with teats pointing slightly outward. The vulva swells and reddens around the same time. Nesting is the unmistakable signal: a sow that suddenly roots up her bedding, pawing and building for hours, is announcing farrowing is 12 to 48 hours out. Once she goes off feed and milk appears, get warm dry spots ready for the piglets, because the litter can start arriving within hours of milk letdown.
The memory aid behind the 114 day figure has its own story and a full date table: see 3 months, 3 weeks, and 3 days explained for how the rule works across the calendar.
Feeding Rules That Change by Stage
Gestation feeding is about restraint, not push. Hold the sow at 4 to 6 pounds of a balanced gestation ration for the first two months, since the piglets are tiny and every extra pound goes onto the sow. In month three, raise the amount gradually as the litter grows, and keep fiber in the ration so sows stay full and calm. In the last week, hold feed steady and many producers trim the ration slightly on the day before farrowing to reduce constipation and udder inflammation. Fresh water without limits is the one rule that never changes, and it matters double once lactation starts.
When to Call the Vet
- Off feed for more than a day in late pregnancy, or a sow that runs a fever.
- Bloody or foul smelling discharge at any stage.
- Strong straining for 30 minutes or more with no piglet presented.
- More than about 45 to 60 minutes of hard labor between piglets once delivery is underway.
- A sow that finishes farrowing with a foul discharge, a fever, or no milk: those piglets need help fast.
If you would rather see the whole year at a glance, our pig gestation chart maps breeding dates to farrowing dates month by month, and the pregnancy confirmation guide covers the early weeks this timeline starts from.
Sources & References
- Merck Veterinary Manual: Swine reproduction and gestation
- University of Minnesota Extension: Swine gestation and farrowing management
- Iowa State University Extension: Sow nutrition during gestation
- Pork Checkoff: Farrowing management resources