Counseling women and men regarding exposures to reproductive and developmental toxicants before conception or women during pregnancy

Life Span, Cause of Death and Neoplasia in B6C3F1 Mice Exposed In Utero to Low- and Medium-Dose-Rate Gamma Rays

Previously, we reported that while low-dose-rate (LDR) gamma-ray exposure to 20 mGy/day for the entire gestation period (gestation days 0-18) did not result in any significant effect in B6C3F1 pups up to 10 weeks of age when compared to the non-irradiated controls, exposure to medium-dose-rates (MDR, 200 and 400 mGy/day) resulted in growth retardation and gonadal hypoplasia, in addition to delayed ossification (only at 400 mGy/day). In the present work, we investigated the late effects of continuous in utero exposure to gamma rays at LDRs (0.05, 1.0 and 20 mGy/day) and at an MDR of 400 mGy/day, on life span, causes of death, neoplastic and non-neoplastic disease incidences in B6C3F1 mice. Reproductive parameters such as litter size and weaning rates was not significantly different among the LDR groups, but was significantly decreased in the MDR group, when compared to the non-irradiated controls. Mean life spans were not significantly different among the LDR exposed groups compared to the non-irradiated controls, whereas the life spans of those exposed to the MDR were significantly shorter than the non-irradiated controls. There was no significant difference in tumor spectra between the non-irradiated and LDR nor MDR irradiated groups. In mice exposed to MDR in utero, the over-all incidence rates shifted with increased incidences in the number of neoplasms of liver (both sexes) and endocrine (adrenals, pituitary and ovaries in females) origin with corresponding decreases in the incidence of malignant lymphomas (both sexes) and lung neoplasms (males). Multiple primary neoplasms were significantly increased only in females exposed to MDR. Results show that B6C3F1 mice exposed to gamma-rays in utero at LDRs of 0.05, 1 and 20 mGy/day for the entire gestation period (18 days) does not significantly alter lifespan, cause of death, neoplasm incidence rates and tumor spectra.

Should pregnant women be included in phase IV clinical drug trials?

Relatively few drugs, especially those recently approved by the US Food and Drug Administration, have published human pregnancy experience. Although all drugs contain animal reproduction data, these are usually not predictive of human risk. Clinical trials in pregnant women are rarely conducted because of ethical and legal concerns, and it may be many years before sufficient observational data are collected to guide clinical treatment decisions. Because many of these drugs will be used in pregnancy, human data are needed shortly after the drugs come to the market. Lack of human data leads to uncertainty over whether a drug can be safely prescribed for a pregnant patient. Unless there are compelling scientific and ethical reasons to exclude them, pregnant women should be included in phase IV clinical trials (postmarketing studies to obtain additional information, including the risks, benefits, and optimal use of a drug). This paper examines how physicians currently counsel pregnant women when there are no human data and proposes an alternative method in which knowledge regarding risks associated with the use of drugs during pregnancy can be enhanced in a clinical trial setting.