Drag to read about a different week.


    Your baby already has everything he needs.

    Embedded zygote in the fourth week

    Your baby’s development

    Zygote, embedded.
    This is it — the week you'll likely miss your period and find out you're pregnant.

    From the 3rd week of pregnancy through the end of the 4th week, your baby grows to the size of a pinhead — about 1/25th of an inch. And there are already three distinct layers from which all of his organs will develop.

    Also during week 4, your placenta begins to form. Made primarily from your baby's tissues, with help from your body’s cells, its primary function is to carry nutrients from you to your baby.

    • The placenta continues to thicken until your 4th month.
    • Although the placenta is made up of shared tissue, your blood and your baby's blood do not come into direct contact.
    A glass of milk

    Your nutrition and health

    Water is your best friend right now.
    Early in your pregnancy, it is important to hydrate, hydrate, hydrate! Your body begins to increase blood volume and your baby needs more fluids. Drinking enough fluids may help you with constipation.

    It is best to choose water or nutritious drinks, such as skim milk, low-fat milk, or 100% fruit juices.

    Have your kale and eat it, too.
    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 tablets include adequate quantities of these micronutrients.
    A woman talking on her smartphone

    Things to think about now

    Schedule an appointment with your doctor.
    If your home pregnancy test came back positive, you should schedule an appointment with your doctor.

    Most doctors will schedule between your 6th and 10th week of pregnancy. To help you get ready for that first appointment, check out this 1st Prenatal Visit Checklist.

    It might seem as if health warnings and pregnancy recommendations are a moving target, because they often are. So ask lots of questions. Being informed is an important part of a healthy pregnancy.
    A woman stretching her leg muscles on the ground

    What happens next week

    Your baby’s heartbeat begins, as does your morning sickness.
    Vital organs are forming, the umbilical cord is taking shape, and your dietary needs begin to change, bigtime.