The "high weight for dates" fetus

The evaluation of abnormal fetal growth patterns has been hindered by the lack of accurate information concerning the rate of intrauterine development at various phases of gestation. In order to overcome this difficulty the menstrual age: crown-rump length ratios of 534 embryos and fetuses between 4 and 160 mm. sitting height, obtained exclusively by therapeutic abortion, have been investigated. On the basis of this study, new growth rate standards have been developed for the sixth to the nineteenth weeks of gestation. The findings were correlated to available data for the nineteenth to the forty-fourth weeks of pregnancy. With the new and reviewed standards for comparison with fetal growth patterns in 441 abnormal gestations, a high incidence of "large for calculated gestational age" fetuses could be demonstrated in connection with early abortion, ectopic gestation, and placenta previa. The evidence indicated that miscalculation of the expected date of confinement because of an apparent menstrual episode after fertilization was the reason for most of these discrepancies. It has been suggested that delayed ovulation and luteal phase defect are the pathogenetic factors responsible for the anomalous postconception bleeding and that these etiologically interrelated phenomena are closely associated with the occurrence of "overripeness" of the ovum.