Billy A. Watson and Kerby C. Oberg
176
Ionizing Radiation
Ionizing radiation can injure the developing embryo due to cell death or
chromosome injury. There is no proof, however, that human congenital
malformations have been caused by diagnostic levels of radiation (Gilbert-
Barness, 2010). As it relates to congenital upper limb anomalies, Wang et al.,
report that in utero irradiation of mouse fetuses on embryonic day 11 (Thaller
stages 18-19, during autopod development) induces a dramatic increase in
autopod malformations. They detected a marked increase in the number of
apoptotic cells in the predigital regions in the forelimb buds 4 hours after
irradiation. Aphalangy (absence of the phalanx bone on one or more digits)
and ectrodactyly (split hand/cleft hand) were the main types of anomalies
observed on day 19 in the limbs of the fetuses irradiated with 5 Gy. (Wang et
al., 1999). In humans, the average radiation dose from an abdominal X-ray is
1.2 mGy and from an abdominal CT scan is 10 mGy, dosages far lower than
those required in the murine model (Lin, 2010). Dosage for radiation therapy
of cancer cells is much greater and varies depending on the type and location
of the cancer. For adjuvant radiotherapy in ovarian cancer, over 45 Gy may be
administered over a one to two-month period (Biete et al., 2010). To avoid any
potential exposure to a developing gestation, female patients of child bearing
potential (~12-50 years old) must be screened and a pregnancy ruled out
before the initiation of radiation therapy (Akintomide and Ikpeme, 2014).
Nutrition
Overnutrition leading to a high body mass index (BMI) can increase the
risk of congenital anomalies. Stothard et al., reported an increased risk of limb
reduction anomalies in gestations from obese women (BMI: >30) compared to
women within the recommended BMI (BMI: 19-25) (Stothard et al., 2009).
Nutrient deficiencies during pregnancy, including those of microminerals and
vitamins as a result of undernutrition or maternal starvation, have been
implicated in a variety of developmental defects (Polin et al., 2011).
Information regarding vitamin and mineral requirements, dietary intake,
and metabolism during pregnancy tends to be lacking, thus making it difficult
to form associations with fetal/maternal outcomes. Deficiencies in
macrominerals such as phosphorous, magnesium, or calcium are rare during
pregnancy (Ladipo, 2000), although the latter may exist in individuals who
avoid a diet rich in dairy products. Low concentrations of magnesium and