In very high doses, it was known at the time that radiation could cause a physiological increase in the rate of pregnancy anomalies, but unlike the dominant linear no-threshold model of radiation and cancer rate increases, it was known, by researchers familiar with both the prior human exposure data and animal testing, that the "Malformation of organs appears to be a deterministic effect with a threshold dose" below which, no rate increase is observed. This teratology (birth defects) issue was discussed by Frank Castronovo of the Harvard Medical School in 1999, publishing a detailed review of dose reconstructions and the available pregnancy data following the Chernobyl accident, inclusive of data from Kiev's two largest obstetrics hospitals. Castronovo concludes that "the lay press with newspaper reporters playing up anecdotal stories of children with birth defects" is, together with dubious studies that show selection bias, the two primary factors causing the persistent belief that Chernobyl increased the background rate of birth defects. When the vast amount of pregnancy data does not support this perception as no women took part in the most radioactive liquidator operations, no in-utero individuals would have been expected to have received a threshold dose.