Teratogenicity

Teratogenic drugs produce structural malformations and functional abnormalities in the developing embryo or fetus. Common teratogenic effects include stillbirth, miscarriage, intrauterine growth restriction, and neurocognitive delay. The severity and type of damage depend on when during fetal development the exposure occurs and which teratogen is involved.

During blastocyst formation, the early embryonic development stage, teratogens can inhibit cell division and kill embryonic cells. This cellular damage can result in the death of the embryo. Teratogens are selective in action, meaning they target specific developmental processes during this critical period.

Organogenesis is a sequential process where embryonic cells differentiate and organize into distinct organs and organ systems. Exposure to teratogens like thalidomide during this period produces specific organ malfunction. The timing of exposure determines which organs are affected and the extent of the structural defects.

During histogenesis and functional maturation, teratogens interfere with nutrient supply or hormonal balance to the fetus. This indirectly causes functional and developmental abnormalities. For example, ACE inhibitors disrupt angiotensin II signaling, which is critical for renal function, leading to fetal malformation and renal failure.

Teratogens are selective in action and exert their effects at specific stages of fetal development. Each developmental stage—blastocyst formation, organogenesis, and histogenesis—has distinct vulnerabilities. Exposure during different periods produces different types and extents of damage, making developmental timing the primary determinant of teratogenic outcomes.

Some teratogens directly affect the differentiation process in developing tissues, leading to skeletal deformities. Teratogenic effects can also include intrauterine growth restriction and neurocognitive delay. The specific malformations depend on which tissues are differentiating when exposure occurs and the potency of the teratogen involved.

ACE inhibitors and angiotensin receptor antagonists disrupt angiotensin II signaling, which is essential for fetal renal function. In early pregnancy, these drugs cause fetal malformation. In later stages, they cause oligohydramnios and renal failure. Understanding effects of chemicals overview helps contextualize how different substances harm developing fetuses.