Trisomy 18: ultrasound findings in 40 cases

OBJECTIVE: We describe the different ultrasound findings suggestive of tris omy 18. PATIENTS AND METHODS: We conducted a retrospective study in 40 cases of tri somy 18 diagnosed in the department of obstetrics at the Lille University H ospital between 1988 and 1998. RESULTS: Eighty percent of the women in this series were multiparous. Mean maternal age at discovery of the trisomy as 33.2 years and the mean gestati onal age was 20.4 weeks. Fifty-five percent of the cases were discovered du ring the second trimester of pregnancy, 22.5% during the third trimester an d 22.5% during the first trimester. One ultrasound abnormality, at least wa s detected in 36/40 cases (90%) a percentage that reached 96.8% taking into consideration the ultrasound examinations performed during the second and third trimesters (30/31 cases). The most frequently detected ultrasound abn ormalities were: intra uterine growth retardation (IUGR: 50%), poly-hydramn ios (42.5%), limb abnormalities (42.5%), cardiac defects (30%), facial abno rmalities (37.5%), meningomyelocele (32.5%), digestive abnormalities (32.5% ), urinary tract abnormalities (27.5%), lymphangiectasia and cystic hygroma (15%), and single umbilical artery (12.5%). Medical termination of pregnan cy (TOP) was performed in 28 cases. There was one spontaneous miscarriage a t 8 weeks and one in utero death (IUD) at 39 weeks in a patient who desired to continue her pregnancy. In 6 cases, the issue of the pregnancy was unkn own because the patients were lost to follow-up. In 4 cases (10%), pregnanc y was continued to delivery of live babies that only survived a few minutes to 7 days. CONCLUSION: The ultrasound signs suggestive of trisomy 18 change according to the term of pregnancy. At the first trimester, most of the signs are non specific, such as cystic hydroma or lymphangiectasia, and do not suggest th e need far a karyotype. At the end of the second trimester, an association of various signs that alone would not be highly suspect suggest the need fo r further exploration in search of other signs: early IUGR, associated or n ot with poly-hydramnios, limb abnormalites, cardiac defects, omphalocele, d iaphragmatic hernia, meningomyelocele, enlarged cisterna magna, choroid ple xus cysts, single umbilical artery, facial dysmorphism, facial cleft, hydro nephrosis.