the wall of the uterus increase its thickness and it also increases its blood vessels, the increase in thickness will help support the fetus or it prevents miscarriage and the increase in blood vessels will allow more blood to flow into the uterus so that the developing fetus will be supplied with nutrients and oxygen
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After fertilization , the union of two gametes, the egg will attach to the uterus then the uterine lining continues to thicken thus pregnancy takes place in this process.
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