ESTIMATION OF GESTATIONAL AGES IN THE COMMON MARMOSET (CALLITHRIX-JACCHUS) FROM PUBLISHED PRENATAL GROWTH-CURVES

This report compares estimated gestational ages from published cubic s pline curves to gestational ages estimated retrospectively from delive ry dates in 28 pregnancies from ten common marmosets (Callithrix jacch us). Both CRL- and BPD-based estimates of gestational age were closely correlated with delivery-based gestational age estimates. Of the thre e ultrasound machines used, the one with 16 shades of gray and a seque ntial linear array overestimated gestational age during early pregnanc y, based on CRL measures. Measures from the other two machines (64 or 264 shades of gray; linear sector and annular array or electronic phas e array) were similar and resulted in a correlation of the two estimat es of gestational age of 0.94 and a mean difference between the two es timates of 0.16 days with 80% of CRL-based gestational age estimates b eing within +/- 5 days of the delivery-based estimate. The reliability of BPD-based estimates of gestational age was strongly related to pre gnancy outcome. BPD-based estimates underestimated gestational age in poor outcome pregnancies (i.e., those in which infants died within 7 d ays of birth) but not in good outcome pregnancies. The combined CRL- a nd BPD-based estimates on poor outcome pregnancies suggest that there was less growth in BPD in late gestation for those pregnancies that re sulted in nonviable offspring. For good outcome pregnancies, the corre lation between BPD-based and delivery-based estimates of gestational a ge was 0.871 and the mean difference between the two estimates was -0. 06 days with 83.3% of BPD-based estimates falling within +/- 5 days of delivery-based estimates.