Your Growing Baby: What Happens When You're 3 Weeks Pregnant

A single-cell zygote forms, divides, and doubles every 12 hours.

Your baby's development

Conception, from A to Zygote.

During your pregnancy at 3 weeks, you might have conceived already. Fertilization occurs when an egg and sperm connect and form a single cell, called a zygote. During your 3rd week of pregnancy:

During your pregnancy at 3 weeks, you might have conceived already. Fertilization occurs when an egg and sperm connect and form a single cell, called a zygote. During your third week of pregnancy:

The microscopic, one-celled zygote repeatedly divides and grows at an astounding pace.
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 baby already has all of the genetic material he/she needs for life — half of the 23 pairs of chromosomes from you and half from your partner.
Your baby's gender is already determined.

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Your nutrition and health

Refocus your nutrition for pregnancy.

Nutrients provide energy to help your baby grow

Folic acid is especially critical during the first 8 weeks of pregnancy for central nervous system and fetal brain development, and remains important throughout the course of your entire pregnancy.

Nutrients provide energy to help your baby grow

Folic acid is especially critical during the first 8 weeks of pregnancy for central nervous system and fetal brain development, and remains important throughout the course of your entire pregnancy.

During this formative stage:

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 stop.

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