Pregnancy › Week by Week › Week 12
At 12 weeks your baby is about the size of a lime, and has just about finished the hardest part: the basic body is built, and from here it is mostly about growing and refining.
Size
A lime
crown to rump
Length
2.1 in
about 5.4 cm
Weight
0.5 oz
about 14 g
Your baby at 12 weeks
The major organs and systems are all in place. This week is about reflexes, fine detail, and practice.
This is a real turning point. Almost every organ and structure your baby needs has now formed, and the weeks ahead are about growth and maturing rather than building from scratch.
Hands and face. Fingers and toes have fully separated, and tiny nails are beginning to grow. The eyes, which started out on the sides of the head, have moved toward the front, and the ears are close to their final position, so the profile is looking much more like a baby and less like an embryo.
Movement and reflexes. Your baby is moving spontaneously and has reflexes: if the roof of the womb is nudged during a scan, the baby will squirm in response. You will not feel any of it yet, since there is still plenty of room, but it is happening.
Inside. The intestines, which spent the early weeks developing inside the umbilical cord, are moving into the abdomen where they belong. The kidneys are working and starting to make urine, and the digestive system is even practicing the squeezing motions it will use to move food one day.
How big is your baby at 12 weeks?
About 2.1 inches (5.4 cm) crown to rump and around half an ounce (14 g).
Measurements this early are taken crown to rump, from the top of the head to the bottom, because the legs are usually curled up. Your provider will use this exact measurement at your dating ultrasound to confirm how far along you are.
Your body at 12 weeks
For many people this is the week the fog starts to lift: nausea eases and a little energy returns.
By around now the placenta is taking over hormone production from the early pregnancy structures, and that shift is often when the worst of the first trimester nausea and bone deep tiredness begin to ease. Not for everyone, and not overnight, but if you have been counting down, this is often where it starts.
Your uterus is growing up and out of your pelvis for the first time. You may notice a small bump starting to show, especially if this is not your first pregnancy, and you may find you are running to the bathroom a little less often as the uterus lifts off your bladder. Other common company this week: a heightened sense of smell, food aversions that are starting to soften, more noticeable veins, and increased discharge, which is normal as long as it is thin and mild.
What is normal, and when to call your provider
Mild cramping and light spotting can be normal in early pregnancy, but call your doctor or midwife the same day if you have any of these:
- Heavy bleeding, especially soaking a pad, or passing clots
- Severe or persistent abdominal or pelvic pain, or strong one sided pain
- A fever over 100.4°F (38°C)
- Severe vomiting where you cannot keep any fluids down, which can be more than ordinary morning sickness and is worth treating
- Fainting, or dizziness that does not pass
Your week 12 checklist
- Go to your dating ultrasound and talk through your screening options beforehand
- Keep taking your prenatal vitamin with folate every day
- Keep meals small and frequent and stay hydrated if nausea is still lingering
- Start thinking about how and when you would like to share your news, if you have not already
- Make time for gentle movement you enjoy, a daily walk counts
Appointments and tests around 12 weeks
The dating ultrasound and first trimester screening usually happen between 11 and 14 weeks.
Your dating ultrasound confirms your due date, checks the baby’s heartbeat, and tells you whether you are carrying more than one. It is often combined with a nuchal translucency (NT) scan and a blood test, together called first trimester combined screening, which estimates the chance of certain chromosomal conditions. Many people are also offered NIPT (a cell free DNA blood test) from 10 weeks, which screens for the same conditions and can reveal the baby’s sex. These are screenings, not diagnoses. If a result needs following up, your provider will talk you through diagnostic options. There are no wrong choices here, and you can accept or decline any of them.
A few things worth having on hand now
A note for your partner
If you can be at the 12 week ultrasound, go. For a lot of partners this is the first time it all becomes real, seeing the baby move on the screen, and it means a great deal to the person on the table to have you there. If you cannot make it, ask for a photo and be ready to hear about it in full when they get home.
You are not alone this week
Twelve weeks can feel like a strange in between: not obviously pregnant to the world, but very much in it. If you have been white knuckling the first trimester, know that reaching this point is genuinely something, and however you are feeling, tired, queasy, wildly relieved, or all of it at once, you are in very normal company.
12 weeks pregnant, common questions
Is 12 weeks the start of the second trimester?
Not quite, though it is close. Week 12 is usually counted as the last week of the first trimester, with the second trimester beginning around week 13 or 14 depending on how it is measured. Either way, you are at the doorstep.
Can I find out the sex at 12 weeks?
Possibly. NIPT, the cell free DNA blood test offered from 10 weeks, can indicate the baby’s sex, and some 12 week ultrasounds make a guess. The reliable confirmation usually comes at the anatomy scan around 18 to 20 weeks.
Is it safe to announce now?
That is entirely your call. Many people wait until around 12 weeks because the chance of miscarriage drops noticeably after the first trimester, but there is no rule. Share when it feels right for you.
Why am I already showing, or not showing at all?
Both are normal. A first time bump often stays hidden a while longer, while a second or third can pop earlier as those muscles have stretched before. Your height, core, and where the baby sits all play a part.
Sources
- American College of Obstetricians and Gynecologists (ACOG), first trimester care and screening guidance.
- Mayo Clinic, Fetal development: the 1st trimester.
- MedlinePlus, National Library of Medicine (NIH), Fetal development and prenatal care.
Medical disclaimer: This page is for information and education only and is not a substitute for professional medical advice. Every pregnancy is different. Always follow the guidance of your doctor, midwife, or qualified provider, and contact them with any concerns.