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.
This process starts before the developing child is even old enough to be considered a fetus, and is instead still an embryo. A developing human is not considered a fetus until the 9th week of development in the uterus, whereas sex differentiation begins during the 6th week of pregnancy. By the sixth week of development, all embryos have both Wolffian ducts and MÃ¼llerian ducts. The Wolffian ducts are embryonic structures that can form the male internal reproductive system.