When do the most important parts of the fetus form?
The first days and weeks after conception are critical for fetus body formation. The most extensive transformation of life occurs before birth. The fetal period goes through major changes. During the third month male or female sexual organs begin to develop and is visible through ultrasound. During months 4-6, the baby’s heartbeat becomes stronger. The digestive and excretory systems begin to develop. Body parts such as the fingernails, toenails, and buds of teeth begin to form and hair grows. Brain development occurs in every prenatal month, but the first three months are crucial. The central nervous system becomes responsive during middle of the women 's pregnancy, and begins to regulate body functions such as breathing and sucking.
Why do substances and circumstance sometimes harm the fetus and sometimes have no impact?
Many factors determine if a substance and circus,stance harm a fetus. these factors include a critical time, frequency of the exposure to the substance and genetics. But some substances for example teratogens, do not cause any…show more content… The first days and weeks after conception are critical for the baby. The health during the entire fetal period affects the brain, and behavioral teratogens affect the fetus at any time. Some teratogens that cause preterm birth or low birthweight are harmful in the second half of pregnancy. A study found that even though smoking cigarettes during prenatal development can harm the fetus, mothers who quit smokers early in pregnancy had no higher risks of birth complications than did women who never smoked. Another study found that binge drinking in the last trimester of pregnancy was more harmful to the brain than during any other period during pregnancy. It is recommended that women avoid drugs, have a diet of extra folic acid and iron, update their immunizations and gain or lose weight before