Background: Improvements in obstetric sonography (US) have led to an increased prenatal detection of clubfoot, but studies have not been able to correlate sonographic severity to clinical deformity at birth. The purpose of this study was to decrease the false positive (FP) rate for prenatally identified clubfeet, and to predict clinical severity using a new prenatal sonographic classification system.
Methods: We retrospectively identified all pregnant patients referred to the fetal care center at our institution for a diagnosis of clubfoot between 2002 and 2007. A total of 113 fetuses were identified. Follow-up information was available for 107 fetuses (95%). Out of 107 fetuses, 17 were terminated or died shortly after birth. Seven patients had normal studies or were not seen at our center. Out of 83 patients, 42 had an US available for rereview. A novel sonographic severity scale for clubfoot (mild/moderate/severe) was assigned by a radiologist specializing in prenatal US to each fetus based on specific anatomic features. The prenatal sonographic scores were then assessed with respect to final postnatal clinical diagnosis and to clinical severity.
Results: None of the pregnancies were terminated because of an isolated diagnosis of clubfoot. Of the remaining 83 fetuses with a prenatal diagnosis of at least 1 clubfoot, 67 had a clubfoot documented at birth (FP=19%). A foot classified as "mild" on prenatal US was significantly less likely to be a true clubfoot at birth than when a "moderate" or "severe" diagnosis was given (Odds Ratio=21, P<0.0001). If "mild" clubfoot patients were removed from the analysis, our FP rate decreased to 3/42. For a subgroup in which postnatal DiMeglio scoring was available, prenatal sonographic stratification of clubfoot did not relate to postnatal clinical severity.
Conclusions: Our initial experience with this novel sonographic scoring system showed improved detection of a true clubfoot prenatally and a decrease in the FP rate. An isolated "mild" clubfoot diagnosed on a prenatal sonogram is less likely to be a clubfoot at birth; this will have substantial impact on prenatal counseling.
Level of evidence: Level III Diagnostic Study.