The problem of neonatal poliomyelitis has attracted considerable attention for a number of years. The writings on this subject abound with statements concerning complete insusceptibility of the fetus in utero to maternal disease, as well as a marked neonatal resistance of the infant to poliomyelitis whether or not the mother was afflicted. Recent reports of epidemic outbreaks involving infants well under 6 months of age and increasingly frequent recording of recognized paralytic and fatal cases in infants born to mothers during the acute phase.of poliomyelitis challenge the validity of these time-honored concepts.
Several years ago, in a discussion of a neonatal paralytic case, it was suggested not only that it is likely that intrauterine infection takes place more often than is generally believed but that "some of the 'normal' infants reported . . . may actually have had mild unrecognized attacks of poliomyelitis." The present study establishes by virus isolation