Growth of the human fetus. II. Abnormal growth in twins and infants of mothers with diabetes, hypertension, or isoimmunization.

Abstract

Abstract As would be expected, the chronic conditions under study have both nonspecific (chronic fetal distress) and specific effects on the fetus. Some quantitative changes amenable to statistical investigation have been studied, relating particularly to the pattern of fetal growth. In addition, information on mortality in relation to fetal growth has been obtained from the deaths within the series of births unselected except for the condition under study, and an additional autopsy series. According to these parameters some characteristics of chronic fetal distress are present in all abnormal groups studied. Growth retardation is most frequent and severe in twins, and considerably less so in fetuses from pregnancies associated with hypertension; however, mortality of growth retarded infants is considerably lower in the former than in the latter. Growth of the brain shows in both groups a pattern of incidence of abnormal weight scores consistent with growth retardation. Weight of the thymus has been studied only in perinatal deaths with normal birth weight, and these were insufficient in number in the two abovementioned groups. While in infants of diabetic mothers overgrowth is common, the brain and thymus are smaller than usual as would be expected in chronic fetal distress with growth retardation. Another puzzling feature is the time of appearance of the abnormalities studied, early in the third trimesten. It is concluded that these infants do not simply show the effects of nonspecific chronic fetal distress and overfeeding although both appear to be involved, but in addition have a specific disturbance, probably endocrine, which modifies their response to both. In isoimmunization the growth pattern of the body is not detectably abnormal but the brain tends to be small (less so than in infants of diabetics) and the thymus also (more so than in infants of diabetics). This suggests, as do other pathologic features, that there is a slight degree of the specific disturbance characterizing infants of diabetics, but greater severity of chronic fetal distress. However, these trends are not strong and cannot be interpreted with assurance.