Sources of indoor pollution include. 1  Mold and pollen. 2  Tobacco smoke. 3  Household products and pesticides. 4  Gases such as radon and carbon monoxide. 5  Materials used in the building such as asbestos, formaldehyde and lead.
After conception, your baby begins a period of dramatic change known as the embryonic stage. This stage runs from the 5th through the 10th week of the first trimester of pregnancy. During this stage, the baby is called an embryo. Your babyâs penis or vagina is visible at the end of the embryonic period, but it's not yet possible to tell on an ultrasound if your baby is a girl or a boy. 2  Muscles and movement. 3  Muscles develop and the embryo begins to move.
3 weeks. Your baby-in-the-making is a ball of cells called a blastocyst. The blastocyst already contains a full set of DNA from you and your partner, which determines sex, eye color, and other traits. 4 weeks. The ball of cells has officially become an embryo and is about the size of a poppy seed. Over the next six weeks, all of your baby's organs will begin to develop, and some will start to function. 5 weeks. Your baby's tiny heart begins to beat â at twice the rate of yours.