4 Weeks Pregnant: Week-by-Week Guide
4 Weeks Pregnant

4 Weeks Pregnant: Week-by-Week Guide

Congratulations! At four weeks pregnant, incredible new developments are beginning to unfold. Check out this week-by-week guide to find out what’s in store for your baby and your body now that you’ve reached the fourth week of pregnancy.

4 weeks pregnant is which trimester? First trimester

How many weeks of pregnancy are left? 36 weeks

4 weeks pregnant is how many months? You’re considered to be in the first month.

With week three of your pregnancy complete, you’re on week four. Enjoy it, as week five is on the horizon!

One of the most exciting things about pregnancy is how many changes you’ll experience with your little one over the span of just seven days! Here are some tips and tricks to keep on top of all that’s happening.

Your baby at 4 weeks pregnant:

What’s happening in there

  • Your baby is the size of a poppy seed.
  • You’re officially at the beginning of the journey.
  • The countdown continues: You've got 36 weeks to go!

What happens during the 4th week of pregnancy?

  • It's all starting to happen: During the first four weeks of pregnancy, all sorts of amazing things begin to grow. It’s time to figure out what you need to eat so you and your little bean get all the vitamins and minerals required to fuel this wonderful process.
  • That's no embryo (yet): Right now, you’ve got a blastocyst growing (it sounds like a “Harry Potter” character). It’s a ball of cells with a hard outer shell and a soft inner shell. The outer shell implants in your uterus and will become the placenta, while the inner shell will be where the embryo—the future mini-you—will develop.
  • Planting the seed: This week, the blastocyst implants itself in your uterus. The lining is thick and ready to nourish the embryo.

What does 4 weeks pregnant feel like?

  • This week is when the blastocyst finds a warm, nourishing place in the uterus to grow. It may lead to a little bleeding, but it’s not a period. It’s part of the effect of the blastocyst implanting into the uterine wall.
  • If you haven’t done a pregnancy test yet, it’s probably time. If it’s positive, be sure to begin scheduling prenatal visits with your doctor.
  • You may feel puffy and bloated, and possibly even start to get morning sickness.

How big is your baby at 4 weeks pregnant?

4 Weeks Pregnant
Baby Weight Too tiny to measure
Baby Length Too tiny to measure
Baby Size Comparable to a poppy seed

Week 4 pregnancy symptoms

During your first four weeks of pregnancy, your body changes quickly. As your baby grows, you will too, and there are certain pregnancy symptoms you may experience at this time.

8 common week 4 pregnancy symptoms

  1. You’ll probably start feeling the symptoms that come with the production of progesterone, a pregnancy hormone that will take top billing in your life, dictating your moods and health.
  2. You may feel a little puffy and bloated.
  3. If you’re a first-time mom, your baby bump probably won’t be showing for a while yet.
  4. There may be some spotting or light bleeding.
  5. You will probably experience some epic mood swings as the hormones kick into gear.
  6. Your breasts and nipples will start to feel tender. They’re giving you a little warning sign that they’ll be playing a major part.
  7. Looking forward to that pregnancy glow? At four weeks, you may start to notice some skin changes, including a luminous glow and natural flush, but most women won’t experience them until the third trimester.
  8. Hormones and your baby’s incredible changes and growing needs may drain your energy, causing fatigue.

You may also have no symptoms yet, and that’s OK. Many early pregnancy symptoms begin popping up around week six.

Can morning sickness start at 4 weeks pregnant?

You probably won’t experience morning sickness during your first four weeks of pregnancy, but it’s coming. Nausea usually kicks in between weeks six and nine, and not just in the morning.

3 tips for week 4 for a healthy and safe pregnancy

Being four weeks pregnant is an important time for you and your baby. Here are some tips on how to adjust to this new stage to keep you and your baby safe.

  • New territory: You’re new to all of this, so make some inquiries to find a good OB/GYN in your area.
  • Quitting bad habits: It’s time to quit those vices. Say goodbye to smoking and drinking.
  • Food for thought: What you eat can impact your baby’s development. A nutritious and balanced diet is important. Check out a clear guide to foods to avoid when pregnant. 

Week 4 pregnancy checklist

Knowing what to do week-by-week can help you feel prepared and alleviate stress. Add these new items to your to-do list this week. You’ve got this, mama!

Week 4 Pregnancy To-Dos Complete
Find your OB
Share the news with your partner, but keep it private for now
Start taking prenatal vitamins

Learn more about your pregnancy, including pregnancy planning and pregnancy nutrition, to feel prepared to continue this magical adventure. You’re armed with the facts and know what to do, so now you can take time to connect with the little one growing inside you.

With week three in the rearview mirror and week four going strong, look to the future and what's coming up in week five!

Join Enfamil Family Beginnings

You’re four weeks pregnant and officially a “mom-to-be.” Start preparing for your new arrival with Enfamil Family Beginnings. It’s the perfect resource for new and expecting moms. Save on Enfamil products, track your bump and baby’s growth, and get helpful articles each week relevant to your journey. Join now for up to $400 in free gifts.