Giving birth is nothing short of a miracle. The placenta, the organ that connects the developing fetus to the uterine wall and allows for waste elimination, nutrient absorption, and gas exchange through the mother's bloodstream, filters out most harmful substances that they threaten the embryo, although some can still be transmitted to the fetus. These harmful substances, called “teratogens,” range from environmental chemicals to the transmission of maternal diseases and can negatively impact the normal development cycle of the fetus. The title “teratogenic,” however, actually refers to any substance or chemical exposure with the potential to cause birth defects in prenatal development. Exposure to teratogenic agents can cause a wide spectrum of physiological and psychological problems in later life, including malformations of the body. (Malformations resulting from exposure to one of the most common teratogens, alcohol, can famously be seen in fetal alcohol syndrome, or FAS, in which patterns of mental and physical defects develop in association with high levels of alcohol consumption during pregnancy. pregnancy.) Although the toxicity of these teratogens is particularly harmful during the fourth and tenth weeks of gestation, teratogens can harm throughout development in the womb. How a teratogen affects the developing human can vary, although nicotine, caffeine, and drug consumption are all directly related. related to physical development. These are examples of habitual teratogens, each of which contributes to low birth weight and behavioral problems in adolescents. The level of influence of a given teratogen depends on many factors; The first, called the “threshold effect,” occurs when a relatively harmless teratogen in small quantities becomes toxic in certain physical deformities, decreased birth weight, and breathing difficulties. The drugs can also have adverse behavioral effects, including high-pitched crying, abnormal sleep, and decreased attention. Studies have established that some children can correct these behavioral inconsistencies, but that change depends on a person caring for them in a nurturing environment. The birth of a healthy baby is a blessing. The prenatal period is susceptible in terms of embryonic development and some exposures to teratogenic agents can have permanent negative effects on the baby. Although the physical outcomes resulting from exposure to teratogens cannot be reversed, it is hoped that some of the behavioral effects of teratogens may have a reduced impact on the child's life, although all mothers should pay particular attention to their child's health during pregnancy..