The effect of sublethal short-duration exposure of paraoxon on pregnancy and fetuses in mice

A convincing number of epidemiological studies have reported on the exposure to and consequences of organophosphorus compounds (OPCs) in pregnant women. However, there is still a knowledge gap and paucity of systematic literature from animal studies. This study was undertaken with the hypothesis that short-duration sublethal exposure to OPCs can produce maternal and fetal lethal effects as chronic exposure. This study examineses the teratogenicity and embryotoxicity of paraoxon (POX) in mice at a dose that is non-lethal to non-pregnant mothers. Pregnant mice were injected intraperitoneally (i.p.) with paraoxon (50 nmol/mouse) on the 4^th and 5^th days of gestation, and the effect of the treatment was assessed on day 18 of gestation. This dose was fatal to pregnant mice in 21% of instances as compared to nonpregnant animals in which 0% mortality was detected, even after daily injection of a similar dose for five days. Significant inhibition of red blood cell acetylcholinesterase (RBC-AChE) was observed in pregnant mice as compared to non-pregnant ones; however, no apparent neuronal effect was detected. Of note were fetal weight decrement, pregnancy termination, intrauterine growth retardation and maternal death. We concluded that exposure to even a non-toxic dose might be critical for pregnant mothers, the pregnancy as well as fetuses. In addition, even exposure of short duration can be detrimental and capable of producing profound and fatal effects.