The blastocyst is firmly embedded in the lining of the uterus. Once this has happened, the placenta (the temporary organ that supplies the growing embryo with oxygen and nutrients) will begin to develop.
Around seven days after fertilization, the blastocyst implants in the lining of the uterus. The outer cell layer, no longer protected, is able to attach to the lining of the uterus. The lining is now more receptive and has undergone changes that make it more "sticky" to aid attachment. The blastocyst erodes cells to sink beneath the surface.
What was originally a single outer layer of cells now transforms into two layers. The outermost layer of cells creates space by eroding the lining, and it secretes hormones. These hormones inform your body that you're pregnant and stimulate the uterus to support the pregnancy rather than shed its lining in what would normally be your period. The innermost cell layer will become the placenta and the amniotic sac that encloses the embryo. Within the blastocyst there is an inner cell mass that will form the embryo.
It can help to relax in this interim period, before you do a pregnancy test. Fill some time by getting in shape with these simple stretches. Getting into the habit of doing these exercises now will help your body deal with the increased demands once you know you're pregnant. Stretch before and after exercising to prevent muscle strain.
Excerpted from Pregnancy Day by Day.
Copyright © 2008 Dorling Kindersley Limited.
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