Pregnancy week by week



Week 4 of Pregnancy

This week the implanted blastocyst gets deeply embedded in the lining of your uterus and the amniotic cavity begins to form. The blastocyst will divide into two parts, one going onto become the placenta and the other transforming into the embryo. The embryo will have three different layers with different types of tissue. The outer layer or ectoderm will go on to form the nervous system, brain, hair, nails, skin, salivary glands, and, sweat glands. While the middle layer or mesoderm will develop into the skeletal system, the circulatory and vascular systems including the heart, blood, and tissues. The inner layer or endoderm will go on to become the lungs, liver, gastrointestinal tract and other organs. The embryo is now approximately one millimetre long; about the size of a poppy seed.

In the meantime, the placenta is also forming and will be delivering oxygen and nutrients to your developing baby. Till the time the placenta becomes fully functional, its functions will be taken over by the corpus luteum (remnants of the ovarian follicle that was containing the ovum). The corpus luteum will produce the pregnancy hormone progesterone until around 12 weeks when placenta will have fully formed.

Your body

By the end of this week, you will be expecting your period to come. However, if you are pregnant your period will most likely not come. Some women do experience some spotting or even a light period; this is called implantation bleeding and is nothing to be concerned about. If you do miss your period, you might begin to think about a possible pregnancy.

If you have conceived, your body will start producing a hormone called human chorionic gonadotrophins (hCG). It is the presence of this hormone in the blood or urine, which will confirm your pregnancy. The pregnancy kit available with the chemist can usually detect this hormone in the urine, though these kits are only 97% accurate. A blood test at this point will detect a positive pregnancy test.

Some of the earliest pregnancy symptoms are very similar to those experienced at the time of your period. You may feel unusually tired, bloated, may have mood swings, slight cramping, or tender breasts. In fact, some women feel like they are just about to start their periods. Refer to our section on first trimester symptoms to read more.


As soon as you discover you are pregnant, you need to schedule your first antenatal appointment with your gynaecologist. These initial few weeks are some of the most important for your baby’s physical development. Your doctor will now plan out your antenatal check-ups and allay your concerns and queries. Ask your doctor about starting prenatal vitamins if you have not done so already.


1) How accurate are the home pregnancy kit and how soon can I take the test?

Home pregnancy tests are 97% accurate and normally give a positive result as early as 10 days after conception. However, for some women the levels of hCG won’t be high enough at this point and may show a false negative test. Therefore, you should ideally repeat the test one week later when the level of hCG has increased sufficiently. However, for the earliest and most accurate result, you will have to get a blood test done for hCG.


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