12 weeks pregnant: symptoms and baby development
Everything is in place. Now it grows.
First trimesterMonth 35 min read
By Solesia, from public clinical guidanceUpdated
You have been carrying a secret for weeks, and this is often the week it stops being one. The first trimester has one more week to run, and for a lot of people the nausea has begun to loosen its grip, which makes the telling easier. Your baby has doubled in length in three weeks and now has everything a person has, in miniature. Your waist is quietly changing shape, though for now it is more a snugness in your jeans than a bump anyone else would see. And appetite, when it comes back, tends to come back with force.
How big is your baby at 12 weeks
About the size of a plum
2.1 in long·0.5 oz
Baby development at 12 weeks
At 12 weeks your baby measures about 2.1 inches and weighs around 0.5 ounces, the size of a plum. The face has a chin now, the eyes have moved fully to the front and sit closer together, and the ears are where they will stay. The gut has finished moving back inside the belly, and the skeleton is turning from soft cartilage into bone at hundreds of points at once.
The first reflexes are here. Touch the palm of the hand and the fingers curl; touch the sole of the foot and the toes spread. The vocal cords are forming in the throat. Deep in the brain, the pituitary gland has started to make hormones of its own, and the bone marrow is beginning to produce white blood cells.
The genitals have developed far enough to be either male or female, but the difference is still too subtle to see on a scan this week. The placenta is now doing the whole job of feeding them and clearing waste, and the heartbeat is strong enough that a handheld Doppler on your belly can usually pick it up.
Your body at 12 weeks
Feeling hungrier as the nausea eases is expected, and the timing is not a coincidence: hCG has dropped from its peak, the placenta has taken over, and your stomach is quieter. Your body needs only about 340 extra calories a day from the second trimester, roughly a sandwich, so appetite is a signal to eat well rather than a lot. Protein at each meal keeps it steady.
A thicker waist is expected too. The uterus has grown up out of the pelvis and can now be felt by your provider just above the pubic bone; it is still too small to show through clothes, but your own hands can tell. Breasts have often gone up a size or more.
Dizziness may still catch you when you stand or after a hot shower, and heartburn after a large meal is common. Both are the same relaxed vessels and muscles as before. Getting up slowly, eating smaller meals and drinking through the day keep them in check.
Common pregnancy symptoms at 12 weeks
- Nausea easing. hCG falling from its peak. Keep eating small and often until it has fully gone.
- Hunger. A quieter stomach and a body building fast. Protein and whole grains, not a doubling of portions.
- A thicker waist. The uterus rising above the pubic bone. Soft waistbands; maternity clothes can wait.
- Heartburn after meals. A relaxed valve at the top of the stomach. Smaller plates, upright after eating.
- Dizziness on standing. Widened blood vessels. Get up in stages and eat regularly.
- Oily or glowing skin. More blood and more oil. Gentle cleanser, sunscreen, and leave it alone.
- Mood swings. Hormones settling but not settled. Better weeks are close.
When to call your provider at 12 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 12 weeks
- The 12-week visit. Usually blood pressure, weight, urine, and a first listen for the heartbeat with a Doppler. If you had screening blood work, results may be back. Visits now run every four weeks until 28.
- Nuchal translucency scan. If you chose it and have not had it, the window runs to 14 weeks. It is done on your belly, usually with a full bladder, and you will see your baby move.
- Sharing the news. Many people tell wider family and friends after this week, but there is no right time. If you would want support if something went wrong, telling earlier is a reason, not a risk.
- Eating with appetite back. Weight gain in the first trimester is usually one to five pounds in total; some people gain nothing and a few lose a little to nausea, and both are fine. From here about a pound a week is the usual pace for a single baby at a normal starting weight.
Common questions at 12 weeks
Is it safe to tell people at 12 weeks?
It is a common time to tell, because early screening is done and by now a pregnancy is very likely to keep going. But there is nothing magic about the number: tell whoever you want, whenever you want. Some tell close family at six weeks and everyone else at twenty. It is a choice about support and privacy, not about safety.
Why has my nausea suddenly stopped at 12 weeks?
Because the hormone behind it, hCG, peaked around 9 or 10 weeks and is now falling, and the placenta has taken over the work that used to depend on those high levels. For some people the sickness fades over a couple of weeks; for others it lifts in a day. Both are ordinary and neither says anything about how the pregnancy is going.
How much weight should I have gained at 12 weeks?
Between one and five pounds in total, and often less if nausea has made eating hard. Some people have lost a pound or two, which is fine as long as fluids stay down. Steady gain begins in the second trimester, at about a pound a week for someone starting at a normal weight, less if starting higher.
Can you see the baby on an abdominal ultrasound at 12 weeks?
Yes. The uterus has risen out of the pelvis and your baby is about two inches long, so a scan on your belly, with a full bladder to lift the uterus into view, shows the head, body, arms and legs clearly, and usually plenty of movement. Very early scans needed the internal probe; from about 11 to 12 weeks that is rarely required.
Written from public clinical guidance, including NHS: Week 12, ACOG: How your baby grows, ACOG: Changes in your body, ACOG: Nausea and vomiting and NHS: Indigestion and heartburn. This page is general information, not medical advice, and does not replace your provider.