Mathematical modeling of fetal splenic growth: use of the Rossavik growth model.

Growth of the fetal spleen has been monitored by measurements of the maximal length (SL), profile circumference (SC), and profile area (SA) of the spleen, from 20 weeks to 41 weeks, menstrual age. Growth curves for these parameters have been determined using a specially developed growth curve model [P = c(t)k + s (t)]. R2 values of 94.3%, 94.9%, and 96.3% were obtained for SL, SC, and SA, respectively. Variability analysis indicated some progressive increase in variability with menstrual age for these three parameters. Variability data were used with the growth curve models to determine standard curves for SL, SC, and SA. These standard curves provide a superior means for evaluating the normal splenic growth in the fetus and for identifying splenic abnormalities in utero.