Analysis of biparietal diameter as an accurate indicator of gestational age

Abstract

To date, there have been 25 studies attempting to correlate biparietal diameter and gestational age; of these, 17 meet specific criteria and thus are included in this evaluation. Although all studies have shown an increase in biparietal diameter with advancing gestational age, between 17 wk and term there is a discrepancy of approximately 3 wk. In this evaluation the charts are compared and the variations analyzed. An ideal table is constructed by combining the mean gestational age, calculated from a statistical analysis, and the variation at each millimeter point, determined by comparison of all the studies. It is hoped that this new 90% composite table, which consists of a range of gestational ages in weeks for each biparietal diameter, will not only provide more realistic indications of fetal age but also will serve as a reminder to sonographers, obstetricians, and patients of the relative accuracy and variations of biparietal diameter measurements.

Foetal kidney length as a parameter for determination of gestational age in pregnancy by ultrasonography

“…Kurtz et al in their review of studies of obstetrical measurements in ultrasound, noted only two earliest studies of fetal kidney length, that used renal time equipment. 4 Two studies i.e. Bertagneli et al and Lawson et al showed their measurement almost equal to our study, and suggested a rule of thumb that is renal length in millimetres approximates gestational ages in weeks.…”

Changes in intracardiac blood flow velocities and right and left ventricular stroke volumes with gestational age in the normal human fetus: a prospective Doppler echocardiographic study.

“…Doppler echocardiograms were obtained from the fetuses from 19 weeks gestation to term. Gestational age was assessed from the first day of the last menstrual period, and was corroborated with ultrasound measurements of biparietal diameter, which has been shown previously to correlate closely with fetal gestational age.16 17 The study protocol was approved by the Brigham and Women's Hospital Human Subjects Committee, and written informed consent was obtained from each mother. Only one pulsed Doppler echocardiographic examination was performed on each mother to minimize any potential harmful effects of repeated ultrasound examinations.18…”

Difference between the left and right ventricular thickness in fetal heart

“…During fetal life oxygenated blood from the placenta is slip-streamed from the ductusvenosus via the inferior vena cava to the left atrium through a widely patent foramen ovale [9][10] . In the presence of such large intraatrial communication preload in the two ventricles must be the same.…”