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.
The fetal period of prenatal development begins on the last day of the eighth week after fertilization and continues until birth. This stage is characterized by the exponential growth of the embryo, now called a fetus, and the development of fully differentiated organs and tissues.etween weeks 13 and 16, the baby begins to move with regularity. Lanugo, a fine, downy hair, begins to grow on the head. Meconium, a thick, dark green waste substance, is produced in the fetus' bowels and remains there (in most cases) until after birth.