13 weeks pregnant: symptoms and baby development
Some find their thumb this week.
First trimesterMonth 35 min read
By Solesia, from public clinical guidanceUpdated
Food tastes like food again. You wake up and the tiredness that has sat on you for weeks is lighter, or gone. The first trimester has this one last week to run, but for many people it already feels like the second. Your uterus has risen far enough that the bathroom trips ease, and low in your belly there may be a small, firm curve that only you would notice. Your baby has spent the last few weeks putting every part in place and is now simply growing into them. A few new things arrive with the extra blood, bleeding gums and a stuffy nose among them.
How big is your baby at 13 weeks
About the size of a peach
2.9 in long·0.8 oz
Baby development at 13 weeks
At 13 weeks your baby measures about 2.9 inches and weighs around 0.8 ounces, the size of a peach. The head is now about a third of their length rather than half, so the proportions are starting to look like a newborn’s. The ribs are forming as fine curved bones, and the arms have grown to a length that is nearly right for the body; the legs are still catching up.
The kidneys are working and producing urine, which passes into the fluid around them, and they swallow that fluid back, a loop that runs until birth and keeps the pool at a steady level. The pancreas has begun to make insulin, and the intestines, settled inside the belly at last, are starting to develop the ridges that will absorb food after birth.
The ovaries or testes are fully formed, and the outer genitals have developed far enough that a skilled sonographer can sometimes make a guess this week, though the anatomy scan at 18 to 22 weeks is when it is clear. The placenta is fully built and, for a short time, weighs more than the baby it feeds.
Your body at 13 weeks
Feeling like yourself again is expected around now, and it can be sudden. Hormone levels have steadied, the placenta is doing the heavy lifting, and the nausea and tiredness of the last two months ease for many people between 12 and 14 weeks. If they have not lifted for you yet, that is expected too; a minority feel sick into the second trimester, and it still tends to fade.
Gums that bleed when you brush, and a nose that is stuffy or bleeds a little, are expected from here on. Both come from the extra blood volume and from hormones that make the small vessels in those linings swell and leak more easily. A soft toothbrush, flossing gently rather than stopping, saline spray and a humidifier at night all help, and none of it is a sign of anything wrong.
A small bump may be there when you look down, especially by evening or if this is not your first pregnancy. It is the uterus, now about the size of a grapefruit, sitting above the pubic bone. Sharp pulls at the sides of the belly when you stand or turn are the ligaments that hold it, and they ease if you move more slowly.
Common pregnancy symptoms at 13 weeks
- Bleeding gums. More blood in swollen gum tissue. Soft brush, keep flossing, and a dental check.
- Stuffy nose or nosebleeds. Swollen lining from extra blood flow. Saline spray, a humidifier, pinch and lean forward.
- Round ligament pulls. Ligaments stretching as the uterus rises. Turn and stand slowly; sit until it passes.
- Constipation. Progesterone and iron. Fiber, water, and a walk every day.
- Feeling hot. More blood and a faster metabolism. Layers you can shed and a fan at night.
- Leg cramps at night. Usually the calf. Flex your foot, toes toward you, and it releases.
- Energy returning. Hormones leveling out. Use it, and keep the early nights anyway.
When to call your provider at 13 weeks
Two things are worth a same-day call at any point in pregnancy: bleeding that is more than spotting, and pain that is severe or does not ease. From the second trimester, add fluid leaking and any change in your baby’s usual pattern of movement. You do not need to be sure something is wrong to call; that is what the number is for.
What to do at 13 weeks
- Pelvic floor exercises. Squeeze as if stopping urine, hold for a few seconds, release; ten at a time, a few times a day, sitting or standing. Starting now makes the last months and the weeks after birth easier.
- Telling your employer. Many people do it after the 12-week scan. Put it in writing once you have told your manager, and ask about leave, adjustments, and time off for prenatal visits. You do not have to tell anyone yet.
- Flu and COVID vaccines. Both are recommended in any trimester and protect your baby for the first months after birth. If flu season is here, this is a good visit to ask for them.
- Moving for 150 minutes a week. With energy back, walking, swimming, cycling on a stationary bike or a prenatal class all count. Anything where you can still talk is the right effort.
Common questions at 13 weeks
When does the second trimester start?
At 14 weeks by the count many providers use, though some say 13 and some 12, because forty weeks does not split into three evenly. Week 13 is the last of the first trimester on the usual count. The second trimester runs to the end of week 27, and it is when many people feel best.
Why are my gums bleeding in pregnancy?
Pregnancy hormones make gum tissue softer and swell the tiny blood vessels inside it, and with half again as much blood in circulation they bleed at the lightest touch. It is called pregnancy gingivitis and it is common. Keep brushing and flossing gently rather than avoiding the tender spots, and see a dentist; cleanings are safe.
Is it normal to still have nausea at 13 weeks?
Yes. Nausea eases between 12 and 14 weeks for many people, but about one in ten still feel sick into the second trimester, and a smaller number for longer. It usually fades gradually rather than stopping. If you cannot keep fluids down or are losing weight, tell your provider; there are safe medicines that help.
Can I sleep on my stomach at 13 weeks?
Yes, if it is comfortable. The uterus is still small and well protected by your pelvis, muscle and fluid, and no position hurts your baby now. Many people find their front uncomfortable from the second trimester and shift to their side on their own. From 28 weeks the advice is to go to sleep on your side.
Written from public clinical guidance, including NHS: Week 13, ACOG: How your baby grows, ACOG: Changes in your body, NHS: Stomach pain, NHS: Morning sickness and ACOG: Nausea and vomiting. This page is general information, not medical advice, and does not replace your provider.