What is the most often observed birth defect resulting from fetal exposure to X-rays?

Microcephaly is recognized as the most frequently observed birth defect following fetal exposure to X-rays. This condition is characterized by a smaller-than-average head size, which can be indicative of reduced brain growth or developmental issues. Exposure to ionizing radiation, such as X-rays, during critical periods of fetal development can disrupt normal cellular proliferation and differentiation in the brain, leading to microcephaly.

In the context of fetal vulnerability, developing neurons are particularly susceptible to radiation damage. The timing, exposure level, and location of the X-ray can significantly influence the degree of risk for various anomalies. While other birth defects may occur due to radiation exposure, the specific association of microcephaly with such exposure makes it the most commonly reported defect.

Other potential effects of radiation exposure, such as genital abnormalities, eye problems, and stunted growth, are recognized, but they occur with less frequency compared to the incidence of microcephaly when assessing congenital outcomes associated with X-ray exposure during pregnancy.