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12 Weeks Pregnant: Week by Week Pregnancy

Symptoms, Tips and Fetal Development


The twelfth week of pregnancy is the last of the first trimester, and moms who’ve been experiencing morning sickness have reason to celebrate: those early pregnancy symptoms like fatigue and nausea are quite likely to let up in the next week or so. Although some women continue to experience nausea throughout their pregnancies, for most the worst is just about over. Here’s what else you can expect when you're 12 weeks pregnant.

Baby at 12 weeks pregnant

If you like to wonder about what your little one will look like, you’ll be excited to learn that the delicate details of his or her face are becoming further defined this week, with tiny chin and nose becoming more refined. Also, tiny fingernails and toenails show up this week!

Your baby’s fully formed (if immature) systems are practicing being functional – the digestive system is contracting, the pituitary gland is producing hormones, and the bone marrow is making white blood cells. Pretty amazing for something the size of a small kiwi fruit (and just 2.5 inches crown to rump!).

Your baby's heart rate is working at around 160 beats per minute when you're pregnant at 12 weeks  – if you have a prenatal appointment this week, you’ll likely hear it for yourself via a fetal Doppler! Although many moms analyze their baby's heart rate to try to determine whether they're having a boy or a girl, this is just an old wives' tale. Instead, your baby's heart is beating so fast (about twice as fast as your own) because the heart is still too small to increase the amount of blood it can pump. To compensate, the heart has to beat faster.

Your body at 12 weeks pregnant

By the end of the week, your uterus will have expanded out of your pelvis and into your abdomen. Put a hand right above your pubic bone and you’ll be able to feel your uterus, which is now the size of a grapefruit. Your waist is probably starting to thicken – that’s not going to stop anytime soon! You might have gained one to four pounds by now. If you haven’t gained anything (or have actually lost weight), not to worry. Most maternal weight gain occurs in the second half of pregnancy. 

pregnancy week 12 embryo
Weekly development of a human embryo at 12 weeks pregnant.

Good news: Your placenta is starting to provide your baby with all his or her nutritional needs. As the placenta continues to take over, this will help relieve your early pregnancy symptoms. Symptoms like fatigue, dizziness, and headaches might stick with you, though, as a side effect of changes in your body circulatory system. It’s pumping harder and faster, and increased blood production is still the name of the game (although at a slower rate than before). 

Have you noticed anything different about your skin in recent weeks? Whether oily and acne-prone or dry and itchy, pregnancy hormones are to blame once again. If you're experiencing dry, itchy skin, slather on the lotion and pay special attention to your belly. Some people think that a moisturized belly reduces the chance of stretch marks developing, but others say it's all about genetics. Either way, a good moisturizer can help relieve itchiness when you're pregnant at 12 weeks. 

12 weeks pregnant ultrasound

At 12 weeks, you might have an ultrasound known as a nuchal translucency (NT). This specialized ultrasound helps determine if your baby has Down syndrome or other chromosomal concerns like trisomy 18 or trisomy 13. In an NT, the technician measures a spot on the back of your baby’s neck called the nuchal fold, and uses that measurement to calculate the probability that your baby has a chromosomal abnormality. The NT ultrasound will also confirm your baby’s gestational age.

How big is your baby at 12 weeks pregnant?

a lime growing on a tree, symbolizing the size of a 12 week fetus

At 12 weeks pregnant, your baby is the size of an lime, on average measuring at 2 inches long and weighing on average at 0.7 ounces.

12 weeks is how many months pregnant? 

At this stage in your pregnancy, you're three months (3m0w) pregnant. 

Common symptoms at 12 weeks pregnant

  • Carpal tunnel syndrome (CTS): The majority of pregnant women – and particularly those who spend their days doing repetitive tasks like typing or punching in numbers – experience CTS, which causes pain, tingling, and numbness in hands. The blame falls on the pregnant body’s swollen tissue, which can press on nerves and cause discomfort. Taking preventative measures to make your workplace more comfortable may help; here are some ideas on office ergonomics for pregnant women
  • Blurred vision: Another seemingly random symptom of pregnancy is blurred vision, which you might have already begun experiencing, and may continue to experience until six weeks postpartum. It’s caused when the outer layer of your eye (the cornea) starts to thicken thanks to fluid retention.
  • Nausea and morning sickness: If this symptom is still on the list for you, you’re not alone: many women don’t feel relief from morning sickness until the first trimester ends (you’re almost there!). Check out these morning sickness remedies and hugs, mama!
  • Fatigue: All the development and changes your body is going through in the first trimester can leave you seriously exhausted or even fatigued. The good news is your energy is almost certain to return during the second trimester, which is days away!
  • Abdominal pressure and mild achiness: You might be feeling some abdominal pressure from your uterus growing, and the increased blood flow occurring in the area. Some mild aches and pains are to be expected from your abdomen these days. The muscles and ligaments around your uterus are also stretching to make room for your baby. Slight cramping is normal, but if your pains are severe, call your doctor right away. 
  • Gas and Bloating: The pregnancy hormone progesterone slows digestion so your body can better absorb nutrients to nurture your growing baby, which is great, but it can also lead to gas and bloating. 
  • Breathlessness: As your baby’s oxygen requirements go up, you might experience some shortness of breath. Your body is adapting to these new demands, but since they are considerable, don’t be surprised if you get winded easily!
  • Congestion: Pregnancy rhinitis – stuffiness and nasal congestion as a result of your pregnancy – is a super common pregnancy symptom, and one that’s likely to stick around. Speak to your doctor before taking any over-the-counter medications for guidance on which are ok to take during pregnancy.
  • Headaches: The changing hormone levels and increased blood circulation in your body can cause headaches and even migraines throughout early pregnancy. If you want to take something for it, acetaminophen (Tylenol) is considered a safe choice for occasional use; ask your doctor what is acceptable usage and dose. Don’t take ibuprofen (Advil, Motrin), aspirin, or naproxen (Aleve), which are not recommended to take at any time during pregnancy.
  • Varicose veins: You’ve probably noticed a map of veins crisscrossing your breasts, legs, and ankles. Your veins are expanding to support the increased blood flow in your body. Some pregnant women develop varicose veins, which are enlarged veins caused by sluggish circulation. Varicose veins are particularly common in women who are overweight or have a family history of them. 
  • Hemorrhoids: An unfortunate side effect of pregnancy are hemorrhoids, which are basically varicose veins in or just outside the anus. They can occur when constipated mamas are straining to go, and can be painful. Find out more about hemorrhoids in pregnancy.

Pregnancy checklist at 12 weeks pregnant 

  • Learn about the Quad Screen: At your next prenatal appointment, your doctor may want to do a quadruple bloodwork screen, aka the quad screen. The quad screen tests for four substances in a pregnant woman’s blood to detect chromosomal conditions such as Down Syndrome or a neural tube defect. The quad screen can be done anytime between week 15-22 of pregnancy, though it’s most accurate when performed between weeks 16-18. Learn more about prenatal genetic testing.
  • Have some sex: As first-trimester symptoms let up, you might find yourself feeling on the frisky side. If you’re feeling it, go for it! Unless your doctor says otherwise, sex during pregnancy is safe. Desire in pregnancy is different for every woman: you might be feeling frisky frequently, not at all, or somewhere in the middle. 
  • Pencil in your due date: At your first prenatal appointment, your doctor or midwife probably calculated a due date for you based on your last menstrual period and your baby’s ultrasound measurements. Although your due date can give you an estimate of when your baby will be born, it's important to remember that a due date is only an estimation. Only five percent of babies are actually born on their due date, so try not to get too hung up on the exact date. Use our due date calculator to estimate your due date.

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