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iVillage Staff on Mar 18, 2010 at 4:30PM
chime in nowDuring this week amniotic fluid begins to collect around your baby in a cavity that will become the amniotic sac. Although your baby is just a rapidly multiplying ball of cells right now, he already has a primitive circulatory system made up of tiny tunnels connecting him to the wall of your uterus.
Get more information on being 3 weeks pregnant.





