Your Weekly Pregnancy Development: Week 4

Your baby's body now has three distinct layers from which all of his organs will develop.

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Get ready for your baby to grow

Week 4: Your baby has embedded in your uterus and is growing at an amazing rate

This is it — the week you'll likely miss your period and find out you're pregnant. Here's what is happening during your 4th week of pregnancy: 

  • Your baby's body now has three distinct layers from which all of his organs will develop.
  • From the beginning of the 3rd week of pregnancy through the end of the 4th week of pregnancy, your baby grows to the length of the head of a pin — about 1/25th of an inch long.

Your placenta's remarkable role

During the 4th week of pregnancy, the placenta, which will carry nutrients from you to your baby, begins to form. It's made primarily from your baby's tissues, with help from cells from your body. Here's a look at what it does:
 

  • During the 4th week of pregnancy, the placenta thickens and continues to thicken until the 4th month of pregnancy.
  • The placenta actually matches the needs of your baby with the specific nutrients available from you at the time.
  • Although it's made up of shared tissue, the placenta does not allow your blood and your baby's blood to come in direct contact.







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Your Week 4 nutrition and health

How to start hydrating properly starting at your 4th week of pregnancy

 

  • Drinking enough fluids is most important early in your pregnancy. Your body begins to increase blood flow and your baby needs more fluids. Drinking enough fluids also can help you fight fatigue and possible constipation.
  • Choose water or nutritious drinks, such as skim milk, low-fat milk, 100% fruit juices, or low-fat fruit smoothies.

The vegetarian mom-to-be

You can follow a vegetarian diet throughout pregnancy, and with careful planning you can get the nutrients you and your baby need. According to the American College of Obstetricians and Gynecologists, vegetarians might need to focus on protein. In addition, supplementation with iron, vitamin B12, and vitamin D is recommended. Check with your doctor to make sure that your prenatal multivitamin and mineral tablet includes adequate quantities of these micronutrients.









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Scheduling with your doctor

  • If your home pregnancy test came back positive, you should schedule an appointment with your doctor. Most doctors will schedule the appointment between your 6th and 10th week of pregnancy. To help you get ready for that first appointment, see our 1st Prenatal Visit Checklist.
  • Getting informed is an important part of a healthy pregnancy, but it might seem as if health warnings and pregnancy recommendations always are changing. Advice you receive now might even conflict with what you’ve learned before. Always consult your doctor about any questions.
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