9.6 Fetopathies

• Overview of fetopathies
• Chemical substances
• Ionizing radiation and hyperthermia
• Infections
• Maternal metabolic diseases

Overview of fetopathies

Fetopathies are fetal damages occurring after embryogenesis has ended and up to the time of birth. Compared with the vulnerability during organogenesis in the embryonic phase the sensibility to substances that can cause abnormalities is less pronounced in the fetal period. Such substances are also termed "teratogenic" and the research in this field "teratology".

Teratogenic substances are divided into the following classes:

• Chemical substances (medications, stimulants, drugs, phytogenic and chemically produced substances such as fertilizers, cosmetics, etc.)
• Ionizing radiation
• Hyperthermia
• Infections
• Metabolic disorders of the mother

Fig. 22
During the embryonic period (A) the degree of sensibility to teratogenic substances is much greater than in the subsequent fetal period (B). The bars above the graph show the vulnerable times for the various organs.

The observation that a substance has teratogenic effects for one species and not for another one or that even within a species differences in sensitivity occur leads one to suspect that there is still another, namely genetic, component to be taken into account. So, for example, the relationship between nicotine abuse and fetal deformities is not a simple, linear one. The chance for abnormalities due to severe nicotine abuse in the normal population is only slightly elevated. If the fetus, though, has a special allele of the gene for the TGF-a growth factor, the damaging substances in the tobacco smoke, which are transferred to the baby via the placenta, can elevate the risk for cleft lip and fusion disorders of the palate (23) 10 fold. Nutrition also plays thereby an important role (24). This example illustrates that teratology is by far not so simple and the research about possible teratogenic substance is much more complex than perhaps commonly thought. Great efforts must be undertaken to research, to understand and possibly eliminate the damaging effects of artificially manufactured substances and their decomposition products that our society produces.