Prospective evaluation of the relationship between gestational age and fetal hand posture in trisomy 18

OBJECTIVE: Trisomy 18 newborns manifest a characteristic hand posture with persistent clenching and overriding of the second, fourth, and Jilth digits. The purpose of this study was to prospectively determine the frequency and severity of abnormal hand posture in fetuses with trisomy 18 at varying gestational ages. STUDY DESIGN: During 1993-1996, 28 fetuses with trisomy 18 had a prospective evaluation of the fetal hand position and posture during a real time sonographic evaluation. The gestational age at imaging varied from 10-40 weeks, and only the first examination of each fetus was used, forming a cross seciional data set. Fisher's exact test was used to compare the incidence of abnormal hand posture between trimesters. RESULTS: Three fetuses were imaged in the first trimester, 20 fetuses were imaged between 15-28 weeks, and five fetuses were imaged between 28-40 weeks gestation. All five fetuses examined in the third trimester manifested persistent clenching of the fingers and overriding of the second, fourth, and fifth digits. None of the three first-trimester fetuses examined was noted to have overriding digits, although one fetus had an absent radius and only three fingers present, precluding the fetus from achieving the characteristic posture. 18 of 20 second-trimester fetuses examined exhibited persistent clenching with 17 of 18 also exhibiting overriding digits. 2 of 20 were noted to open their hands and fully extend all five fingers on real time imaging. P-value s were significant (P = .006} when comparing the first and second-trimester, but not significant when comparing the second and third trimester. CONCLUSION: This study suggests that the hand clenching and overriding fingers seen in trisomv 18 newborns first appears in the early second trimester and is present in nearly all fetuses bv mid-trimester.