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The four most common teratogens are tobacco, alcohol, medications and illegal drugs. Teratogens are substances that could harm a developing fetus by affecting growth and causing birth defects or death. The use of tobacco during pregnancy is dangerous because the smoke causes the blood vessels to constrict.


often times results in an “all or none effect.” That is, the effect of the teratogen, if it is to have any effect, will be so profound as to cause a spontaneous abortion. Some examples of teratogens known to cause human malformations are listed in the table below (Table 23-2). A few of the most common examples will be discussed below. Table ...


Pregnancy and Teratogens. Medically reviewed by Janine Kelbach, RNC-OB on March 4, 2016 — Written by the Healthline Editorial Team. Teratogens are drugs, chemicals, or even infections that can ...


What are the most sensitive periods for teratogens in pregnancy? Once the egg is fertilized (conception), it takes about six to nine days for implantation (anchoring into the uterus) to occur. Once the fertilized egg is connected to the uterus, a common blood supply exists between the mother and the embryo.




A teratogen is any agent that causes an abnormality following fetal exposure during pregnancy. Teratogens are usually discovered after an increased prevalence of a particular birth defect. For example, in the early 1960’s, a drug known as thalidomide was used to treat morning sickness. Exposure of the fetus during this early stage of development resulted in cases of phocomelia, a congenital ...


à other teratogens are harmful at any time during the pregnancy---for example, for behavioral teratogens, there is no safe period---the brain and nervous system can be harmed throughout the pregnancy . critical period---in prenatal development, the time when a particular organ or other body part is most susceptible to teratogenic damage


Hazards to Prenatal Development: Teratogens •Teratogens are any agents from the environment that can cause harm to the developing fetus. •Many harmful agents cause damage only if exposure occurs during a sensitive period of prenatal development.


Additionally, teratogens may also affect pregnancies and cause complications such as preterm labors, spontaneous abortions, or miscarriages. Teratogens are classified into four types: physical agents, metabolic conditions, infection, and finally, drugs and chemicals. The word teratogen originates from the Greek word for monster, teratos.


Some teratogens are benign until they build to "threshold concentration" levels in the mother and then their effects are seen. Some teratogens are dangerous throughout a pregnancy and some are dangerous only at specific points of embryonic development. The only safe course of action is to actively avoid known teratogens before and during pregnancy.