It could also be due to premature embryonic death causing less pups to make it to term. (pethelpful.com)
«Just as deletion of the Sox2 gene causes the very early embryo to die, it is likely that an abnormality in the regulatory region would also cause early embryonic death before any of the organs have even formed,» said Mitchell. (sciencedaily.com)
Female - Biased Embryonic Death from DNA Replication Stress - Induced Inflammation Presented by Adrian McNairn, PhD Postdoctoral Associate - Schimenti Laboratory Department of Biomedical Sciences Cornell University Ithaca, NY (www2.vet.cornell.edu)