Your Weekly Pregnancy Development: Week 3

The microscopic-sized zygote divides again and again, growing at an astounding pace

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A little zygote forms

Week 3: Your fertilization and implantation

Although you don't know it yet, you might have conceived already. Fertilization occurs when an egg and sperm connect and form a single cell, called a zygote. Here's what is happening during your 3rd week of pregnancy:

  • The microscopic-sized zygote divides again and again, growing at an astounding pace.
  • Your baby already has all of the genetic material she needs for life — half of the 23 pairs of chromosomes from you and half from your partner.
  • Your baby's gender already is determined.

Cell division and repetition

Approximately 12 hours after fertilization, your baby — right now, only a one-celled zygote — divides into two identical cells. These two cells each split, creating four cells, which then split to become eight. This process continues as the total number of cells in your baby doubles every 12 hours. While this division occurs, your zygote is moving down the fallopian tube to your uterus.


Your Week 3 nutrition and health

Refocus your nutrition to account for your pregnancy

Even prior to the 3rd week of pregnancy, how well you eat and care for yourself make a big difference in the quality of nutrition your baby receives. 

What do the nutrients in your food do?

  • Calories provide energy to help your baby grow.
  • Iron helps make the extra blood needed during pregnancy.
  • Folic acid is critical during the first 8 weeks of pregnancy for central nervous system and fetal brain development.
  • Protein helps produce blood and builds your baby's tissues and muscles.
  • Calcium and vitamin D work together to build your baby's bones and teeth.

At 3 weeks pregnant, remember:

  • Continue to take your doctor-recommended folic acid supplement or prenatal multivitamin.
  • Drink plenty of fluids.
  • Respond right away if your body indicates that you should slow down or even stop.
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Exercise and pregnancy

If you're already in good condition and regularly exercising, pregnancy shouldn’t prohibit you from continuing a safe exercise routine.

Good exercises for women in their 1st trimester of pregnancy include:

  • Walking
  • Swimming
  • Aerobic Activity

Also, please consult your doctor before starting any new physical exercise.

Keep learning about your baby's development every week
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