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.
During this stage, all of your baby's major organs and body parts begin to develop. The cells of the embryo (called embryonic stem cells) multiply and change into the hundreds of different types of cells needed to make a whole human body.The placenta also develops during the embryonic stage. This is one of the first things to develop during the embryonic stage. 2  This means your babyâs brain, spinal cord and nerves form during this stage. 3  Heart. 4  An S-shaped tube forms on the front of the embryo.