During which stage of fetal development is exposure to teratogens most damaging?

Prenatal Environmental Influences

The complex process of prenatal development demands the care of parents to create a safe environment for their ongoing development in the womb. Many different factors can affect the embryo and fetus.

Teratogens

Teratogen is defined as any environmental agent that causes damage during the prenatal period. The amount of home darn depends on:

• Dose amount - higher risk of negative effects if large doses over long periods of time
• Heredity - based on genetic makeup, some people are better than others at withstanding harmful agents
• Age - if the organism is exposed during a sensitive period of development, the likelier damage is to occur
• Other negative influences - multiple negative factors can worsen impact of each harmful agent

Each prenatal stage has a sensitive period in which development is especially susceptible to damage. In the period of zygote, teratogens have little impact. Serious damage is most likely to occur during the embyronic period because that is when foundations for body parts are developed. The affects of teratogens during the fetal period is minor, but may still cause abnormalities in the brain, ears, teeth and genitals. 

Most commonly used/researched teratogens:

• Prescription and non-prescription drugs 
• 1960s sedative used to help with morning sickness, thalidomide, produced devastating deformities of embryo's arms, legs, ears, heart, kidneys
• 1945-1970 synthetic hormone used to prevent miscarriages, diethylstilbestrol, caused consumer's daughters to have unusually high rates of cancer of the vagina, malformation of the uterus, and infertility. 
• Accutane, used to treat severe acne, is the most widely used teratogen. If exposure occurs during the 1st trimester, abnormalities may form with the ears, eyes, skull, brain, heart, and immune system.
• Regular Aspirin use is linked to low birth weight, infant death, poor motor development, and lower intelligence scores.

• Illegal Drugs - pregnant women who use drugs put their child at risk for prematurity, low birth weight, physical defects, problems breathing, and infant death.
• Tobacco - tobacco use during pregnancy is directly linked to low birth weight and increases the likelihood of miscarriage, prematurity, and breathing problems.
• Alcohol - prenatal alcohol exposure causes fetal alcohol spectrum disorder, a range of physical, mental, and behavioral outcomes. The syndromes are distinguished by slow physical growth, facial abnormalities, and brain injury.
• Radiation - Exposure to radiation can result in miscarriage, underdeveloped brains, physical deformities, and slow physical growth.
• Environmental Pollution - Mercury, lead, and dioxins are among the list of polluting chemicals that can impair prenatal development. 
• Infectious Disease - most seem to have little impact, except for rubella, HIV, herpes, and toxoplasmosis. 

Other maternal factors:

• Nutrition - the poorer the prenatal diet of the mother, the greater loss in the baby's brain weight. Healthy weight gain during pregnancy is 25-30 lbs and folic acid is important in neural tube development.
• Emotional Stress - Intense stress during pregnancy can cause miscarriage, prematurity, cleft palate and heart deformities.
• Maternal Age - Women who wait until 30s or 40s to have children, have an increased risk of infertility, miscarriage, and chromosomal defects.

Prenatal care is crucial in making sure you have the healthiest and safest pregnancy possible for you and your baby. Regular doctors visits are used to track weight gain, general health, and to check on the status of the cervix and uterus. Some women need careful monitoring, such as diabetics and those with preeclampsia. 

Many women do not seek prenatal care due to lack of medical insurance, financial hardships, difficulty finding a doctor, and many other personal barriers. However, there are many programs and services to aid pregnant women, such as WIC and MediCal. Prenatal care, a healthy diet, a low stress environment and avoiding teratogens are crucial to ensure a healthy prenatal environment for your growing baby.

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