of Radiation on the Embryo and FetusYvonne Pham and Steven Oh

EFFECTS OF RADIATION ON THE EMBRYO AND FETUS

YVONNE PHAM AND STEVEN OH

Question 1

What are some effects that radiation can have on a developing embryo and fetus?

Question 2

Are the effects of irradiation during gestation considered deterministic or stochastic in nature?

Question 3

What is the baseline incidence of congenital abnormalities for infants in the general human population?

Question 4

What are the three developmental stages in utero that are typically considered in the context of radiation exposure?

Question 1 What are some effects that radiation can have on a developing embryo and fetus?

Answer 1

Radiation can cause lethal effects (prenatal or neonatal death), hereditary defects, carcinogenesis, congenital malformations, growth disturbances, and mental retardation to occur in a developing embryo and fetus.

Hall EJ, Giaccia AJ. Effects of radiation on the embryo and fetus. In: Hall EJ, Giaccia AJ, eds. Radiobiology for the Radiologist. 7th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2012:174–187.

Question 2 Are the effects of irradiation during gestation considered deterministic or stochastic in nature?

Answer 2

The effects of irradiation during gestation, such as prenatal death and congenital malformations, are considered deterministic in nature since certain dose thresholds are necessary to cause these effects and the degree of severity is dependent on dose. In contrast, carcinogenesis from in utero irradiation is considered a stochastic effect in that there is no threshold dose and the severity is independent of dose.

Question 3 What is the baseline incidence of congenital abnormalities for infants in the general human population?

Answer 3

The baseline risk of congenital abnormalities is 5% to 10%. Thus, it is difficult to determine if exposure to a small dose of radiation in utero is solely responsible for an existing congenital abnormality.

Question 4 What are the three developmental stages in utero that are typically considered in the context of radiation exposure?

Answer 4

1. Preimplantation is the period of time from fertilization to implantation of the embryo into the uterine wall and occurs during days 0 to 9 postconception.

2. Organogenesis is the period of development of major organs and takes place from day 10 to week 6 postconception.

3. The fetal period encompasses the growth of organs that have been formed and occurs from week 6 postconception until term.

Question 5

What stage of development in rats and mice is most sensitive to the lethal effects of radiation?

Question 6

Which stages of radiation exposure generally result in prenatal and neonatal death, respectively?

Question 7

What is considered the threshold radiation dose for animals in utero thought to produce growth retardation?

Question 8

What is considered the threshold dose for central nervous system (CNS) damage for a mouse in utero?

Question 9

Radiation exposure during which stages of gestation for a mouse would result in temporary and permanent growth inhibition, respectively?

Question 5 What stage of development in rats and mice is most sensitive to the lethal effects of radiation?

Answer 5

The preimplantation stage is most susceptible to the lethal effects of radiation in mice and rats. There is thought to be an “all or nothing” effect of radiation during this stage in which an irradiated preimplanted embryo will grow normally if it survives but will otherwise result in death of the embryo if too many cells are killed by irradiation.

Question 6 Which stages of radiation exposure generally result in prenatal and neonatal death, respectively?

Answer 6

Prenatal death, which occurs before birth, generally results from irradiation during the preimplantation period. Neonatal death, which occurs around the time of birth, generally results from irradiation during organogenesis.

Question 7 What is considered the threshold radiation dose for animals in utero thought to produce growth retardation?

Answer 7

1 Gy of x-rays is thought to produce growth retardation during organogenesis and the fetal period. Studies have shown that a dose of 0.25 Gy is not high enough to cause an observable effect on growth.

Question 8 What is considered the threshold dose for central nervous system (CNS) damage for a mouse in utero?

Answer 8

0.1 Gy is thought to produce CNS damage according to mouse data.

Only gold members can continue reading. Log In or Register to continue