Pregnancy Week 4

Woman who is 4 weeks pregnant

4 Weeks Pregnant: The 4th Week of Your Pregnancy

Congratulations! Weeks four through seven are when most women discover they are pregnant. This week-by-week newsletter will keep you informed about what to expect during your pregnancy. If you have just found out that you are pregnant, you may want to begin by reading weeks 1 through 3.

How is pregnancy calculated?

There can be a lot of confusion when discussing the way in which pregnancy is calculated. Since most women do not know when they conceived as it is challenging to know exactly when ovulation occurred, pregnancy is calculated from the first day of your last menstrual period (LMP).

Counting from your LMP, your pregnancy will last around 40 weeks. For more information on how pregnancy is measured, please see our information on calculating your dates.

What changes are occurring in your body?

You may begin to exhibit some early pregnancy symptoms such as breast tenderness, headaches, lower backaches, and nausea. It is important to know that many early pregnancy symptoms are similar to those you may experience before your period.

Other women may not have any pregnancy symptoms except for a late or irregular period. If you have missed your period, then you could take a pregnancy test. This would be the earliest that a home pregnancy test can detect pregnancy.*

What is happening with your baby?

There are three layers to your baby- the ectoderm, mesoderm, and endoderm. These three layers will form the baby’s organs and tissues. The ectoderm will become the nervous system (including the brain), skin, hair, nails, mammary glands, sweat glands, and enamel for the teeth.

The mesoderm will become the heart, circulatory system, skeleton, connective tissues, blood system, urogenital system, and the muscles. The endoderm will house the lungs and develops into the lining of the gastrointestinal tract, the liver, pancreas, and thyroid.

Arm and leg buds begin developing at this point, although they are not clearly distinguishable. The placenta has also begun to form and is producing some important hormones including hCG. There is movement of rudimentary blood through the main vessels.*

How big is your baby?

Babies are still very small at this point and measure about 0.078 inches (1.98 millimeters) in length.*

What should you plan for this week?

If your period is late or if you have an irregular period, you may want to take a home pregnancy test. If the result is positive, you can try to schedule an appointment with a health care provider, although many health care providers wait to see you until you are 8 to 12 weeks pregnant.

If your test is negative and your period is late, then you should wait a week before testing again. Some women take 2 to 3 weeks after a missed period before producing a detectable level of the pregnancy hormone.

You also want to begin looking for a health care provider and decide where you will have your baby. Many doctors and midwives will allow you to arrange an appointment so you can meet them and ask questions before deciding if they will become your provider. For more information on choosing your health care provider, see our information on your birthing choices.

Tips for making your pregnancy better

If you have not begun an exercise routine, check with your healthcare provider to see what he/she recommends. Even if you already have a routine, you might want to read about exercise during pregnancy.

Take a look at our information on:

You also want to be careful about the different medications you take during pregnancy. You should check with your health care provider before taking any over-the-counter or prescription medications.

Your prenatal vitamin should contain at least .4 mg (400 micrograms) of folic acid. Prenatal vitamins normally contain .8 mg to 1 mg ( 800 micrograms to 1 millogram) of folic acid and also have a high iron content. These are important for both you and your baby.

Tips for mom’s partner

Continue being open with your partner about your fears and excitement about her being pregnant. Talk about when you want to share the news with family and friends.

Last Updated: 07/2015