Isolated echogenic foci in the fetal heart: do they increase the risk of trisomy 21 in a population previously screened by nuchal translucency?

Objectives To confirm the hypothesis that isolated cardiac echogenic foci a t the second-trimester anomaly scan do not influence our current calculatio n of risk of trisomy 21 in individual pregnancies, which is based on matern al age and nuchal translucency thickness at 11-14 weeks. Design Observational study in a fetal medicine unit. Methods In a general pregnant population undergoing first-trimester nuchal translucency screening, data from 239 singleton pregnancies with isolated c ardiac echogenic foci at the second-trimester anomaly scan were compared wi th those of a control group of 7449 pregnancies with normal anomaly scans. Prevalence of trisomy 21 was determined in both groups. Following the anoma ly scan, the individual risks of trisomy 21 were calculated by adjusting th e previous risk based on maternal age and first-trimester nuchal translucen cy. We assumed that echogenic foci did not alter each individual risk calcu lation. The expected number of cases of Down syndrome in both groups was th en calculated from the sum of probabilities of each individual affected fet us. The observed number of cases was compared with the expected number in b oth study and control populations. Results There was no statistically significant difference between the Preva lence of trisomy 21 in the study group (no cases) and in the control popula tion (three cases). From individual risk calculations, observing no cases o f trisomy 21 in the study group was the most likely event if echogenic foci did not increase the risk of this chromosomal abnormality (P = 0.62). Conclusion The finding of isolated echogenic foci at the time of the 20 wee k-scan does not significantly change the risks of trisomy 21 if background risk and previous nuchal translucency measurements are taken into account i n the individual risk calculation. We suggest that no further adjustments t o risk should be used.