4 Weeks Pregnant: Symptoms & Baby Development - Babylist
4 Weeks Pregnant
June 7, 2022

4 Weeks Pregnant

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4 Weeks Pregnant

How Big is Your Baby at 4 Weeks?

Your baby is less than 0.05 inches long this week. That’s the size of a poppy seed.

Here’s what else to know when you’re 4 weeks pregnant:

Your Baby’s Development at 4 Weeks

If you were to look at baby on an ultrasound at 4 weeks, you wouldn’t see much, but there’s actually a lot going on at this very early stage of your baby’s development. The fertilized egg has implanted into your uterus, and it’s quickly beginning to grow.

  • Splitting in two: This week, the blastocyst (which is basically a collection of cells) is splitting, eventually turning into your placenta (a whole new organ) and an embryo (hi, baby!).
  • Prepping for development: Even though it’s a tiny dot of a thing that can barely be seen on an ultrasound, the gestational sac carries blueprints for your baby’s nose, toes and just about everything else hidden in their chromosomes.

4 Weeks Pregnant Ultrasound


Top Tip for 4 Weeks Pregnant

Add a prenatal vitamin with 600 mcg of folic acid to your daily routine (if you aren’t already taking one). Folic acid protects against birth defects and may even lower your child’s blood pressure when they grow up.

Your Body: 4 Weeks Pregnant Symptoms

  • PMS vs. pregnancy symptoms: In those early days, many women find pregnancy symptoms tough to decipher from the typical PMS symptoms. After all, moodiness, fatigue, sore breasts, bloating and constipation can all be signs of PMS. But PMS eventually leads to a period and then goes away. Pregnancy symptoms linger—usually for the first trimester. Unsure? The only way to really know you’re pregnant is to take a pregnancy test
  • Missed period: It’s so early that you might not feel pregnant yet, but oh wait? Where’s Aunt Flo? Missing your period may be the first telltale sign of pregnancy and your motivation to take a pregnancy test.
  • Positive pregnancy test: Some home pregnancy tests are accurate at this point, but it could take another few days or even a week before you have enough hCG (a pregnancy hormone) in your urine for an at-home test to detect. If the at-home test was negative, you could schedule a blood test (which is super sensitive) at your doctor’s office or lab, or test again a few days later with another pee stick. If the at-home test was positive, you can feel pretty confident you’re pregnant.
  • Sore breasts: Before nausea, vomiting and extreme fatigue, what do many women notice? Sore or swollen breasts. It’s hard to believe that your body is already prepping for feeding a baby as early as 4 weeks but it is.
  • Fatigue: A pregnancy hormones surge and your body starts to produce more blood to nourish baby, you’re bound to feel more than a little tired. In fact, you may be downright exhausted.
  • Spotting: About 30% of women experience implantation bleeding when the embryo attaches to the wall of the uterus, so don’t be surprised if you have some light spotting. The bleeding tends to be a different color from a period, like light pink or dark brown.
  • Light cramps: Implantation cramps are also a thing. These mild aches should only stick around for a day or two.

Not feeling symptoms yet? You’re not alone. But during the first trimester, hormones surge and your body works hard to start making a baby. You find yourself experience these symptoms in the coming weeks:

  • Nausea and vomiting: About half of pregnant women get morning sickness (which really should be called all-day sickness); it usually crops up around week 6 and eases around week 12.
  • Food aversions: What goes hand-in-hand with the nausea? Getting grossed out by foods you used to love. You may find yourself majorly changing your eating habits.
  • Frequent urge to pee: Around 6 to 8 weeks, hormonal changes + extra blood flow causes kidneys to produce more urine than usual, so you might be heading to the bathroom a lot.
  • Constipation: A slow-down in your intestines can happen, and sometimes the iron in prenatal vitamins can stop you up. Load up on fiber and water, and try to stay physically active. Walks are your friend!
  • Mood swings: You’re tired, your metabolism is changing, you may be a bit stressed and hormones are wacky right now. It’s no wonder you cried at that Oreo commercial.

While these are all par for the pregnancy course, know that some pregnant women don’t get first trimester symptoms at all. Lack of symptoms doesn’t mean anything’s wrong—just that every pregnancy is different.

Fun Fact

Four babies are born every second!

Your Life at 4 Weeks Pregnant

Over the next nine months, your body is going to be hard at work making a new little person. But it’s important to remember you’re still a person, too, and prioritize some time for you. Here are some ideas.

  • Top tip: Take time for yourself—and your partner, if you have one—to process this major milestone. You’ve just learned some serious life-altering information! You may not be ready to share your news yet, but if you feel like it, spend some time reflecting on your feelings. Write down what you’re experiencing as a journal entry or a letter to your future self, or share it with your partner or a friend on a long walk or over a quiet dinner at home.
  • Entertain yourself: Speaking of feelings, your mind may start working on overtime trying to imagine the next nine months—not to mention, how things will be once your baby arrives. It’s still early, so if you find you’re getting ahead of yourself, slow down with a bingeable baby-free series. Check out Schitt’s Creek or Broad City to distract yourself with some laughs.
  • Get ready: Whether you’re excited, nervous or everything in between, think about prepping for what’s to come, and check out some new-school baby books for a modern approach to pregnancy and motherhood. Expecting Better and Bringing up Bebe are good places to start.
  • Chow down: According to the American Pregnancy Association, more than 50 percent of women will experience morning sickness at some point in their pregnancy. The good news? It usually doesn’t start ramping up for a few weeks. In the meantime, have dinner at one of your favorite restaurants and celebrate your appetite.

Your Pregnancy, Week by Week

Want to know what’s going on with both your baby and your body every week? Start your Babylist registry today and get friendly tips and expert advice delivered right to your inbox for each week of your pregnancy (and beyond!).

4 Weeks Baby Bumps from Real Moms


4-weeks-pregnant-bump-@faith in the wait








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4 Weeks Pregnant Checklist

  • Take four more home pregnancy tests. Just kidding! One’s enough.
  • Call your OB/GYN and make an appointment for your first prenatal visit, which will probably take place around week 8.
  • Whether you’ve been trying for months or this is a surprise, remember to take a deep breath. This is going to change everything, but that’s the point.
This information is provided for educational and entertainment purposes only. We do not accept any responsibility for any liability, loss or risk, personal or otherwise, incurred as a consequence, directly or indirectly, from any information or advice contained here. Babylist may earn compensation from affiliate links in this content. Learn more about how we write Babylist content and the Babylist Health Advisory Board.