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Week 5 of Pregnancy: Week by Week Pregnancy Calendar

Your baby is now the size of a sesame seed. He or she looks more like a tadpole than your son- or daughter-to-be, but, rest assured: Your baby will begin to develop human characteristics sooner than you expect. (And, yes, the tail will eventually disappear!) You are in your second month of pregnancy.

Your Baby

Embryo During Week 5 of Pregnancy

Embryo During
Week 5 of Pregnancy

During week 5 of pregnancy, your baby consists of about 125,000 cells but is still very tiny, measuring only about 0.05 inches in length. The three layers of the embryo—ectoderm, mesoderm, endoderm—continue to develop into your baby’s organs including the lungs, liver, and pancreas. From the ectoderm develops the neural tube, which will become your baby’s brain and spinal cord. Even more amazing, a tiny heart forms from the mesoderm during week 5 of pregnancy and begins to beat and pump blood, although your baby’s heartbeat will not become regular for another few weeks. A primitive placenta and umbilical cord have begun supplying oxygen and nutrients to the rest of the embryo. Amniotic fluid begins to fill the amniotic sac surrounding the embryo.

Your Body

Embryo at 5 Weeks

Embryo at 5 Weeks

You have now missed your period. If you have not taken one yet, a home pregnancy test (HPT) should give you a positive during week 5 of pregnancy. As hCG (human gonadotrophin hormone) continue to rise in your body, you may find yourself feeling more tired than usual. You may also find yourself making more than a few extra trips to the bathroom beginning this week as a result of the new cocktail of hormones circulating through your body. Your clothing may also be a little snugger starting this week; however, all that bloating is caused by your hormones and the extra blood that your body is producing to sustain your pregnancy, not by any significant growth by your little womb-raider. And, if you find yourself feeling more irritable or moody than usual, you can once again blame those hormones.

Also during week 5 of pregnancy, you may notice that your breasts are tenderer or even painful to touch. Your areolas, the darker circles around your nipples, may also be darkening as your breasts prepare to produce milk after your baby is born. And, if your breasts are not yet bothering you, you may find yourself dealing with another icky symptom of pregnancy: morning sickness. Contrary to the name, nausea during pregnancy can affect a woman at any time of the day. Furthermore, although morning sickness is never fun, about one out of three hundred women will experience hyperemesis gravidarum, which is a severe form of pregnancy-induced nausea that results in weight loss. Fortunately, morning sickness usually subsides by the end of the first trimester.

Sesame Seeds

Baby Is the Size of a Sesame Seed
During Week 5 of Pregnancy

Learn about your baby during week 4 of pregnancy or week 6 of pregnancy.

Disclaimer: The information provided in this article is not meant to replace the professional medical advice of your health care provider.


Curtis, Glade B. & Judith Schuler. 2011. Your pregnancy week by week. 7th edn. Philadelphia: Running Press.
Stone, Joanne & Keith Eddleman, eds. 2003. The pregnancy bible: Your complete guide to pregnancy and early parenthood. Willowdale, Ontario: Firefly Books.
Week Five: The embryonic stage begins:
Your pregnancy: 5 weeks:
Your pregnancy week by week: Weeks 5-8:

Image Credits

Embryo During Week 5 of Pregnancy:
Embryo at 5 Weeks:
Sesame Seeds:

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