You still may not know you are pregnant by week three, but your baby is developing in leaps and bounds.
During the last week the eggs has divided hundreds of times and become a hollow, fluid filled blastocyst. The blastocyst is barely visible to the naked eye. Between days 4 and 7 the blastocyst will implant itself into the endometrium which will eventually become the placenta. You may have a small bit of spotting when the blastocyst implants itself. You might think you’re period is starting, but this spotting is usually a very small amount and only lasts a day or two.
By the end of this week your egg has become an embryo and would be visible to the naked eye, being about the size of the head of a pin. While this embryo doesn’t look anything like a fetus or a baby at this point, the brain, backbone, and the cardio-vascular system – complete with a beating heart are beginning to form! If looked at very closely you would be able to see a form the shape of the sole of your shoe, with a head fold on either side near the top.
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