Chromosome variation in perinatal mortality: a survey of 500 cases

SUMMARY The results of chromosome analyses on 500 cases of perinatal deaths are reported. It was found that 4- 8 % were chromosomally abnormal, but 900 % of the chromosomally abnormal were either clinically malformed or macerated fetuses. Of the macerated fetuses, 9 % were chromosomally abnormal and of these 330 % had trisomy 21. The data suggest that the high loss of trisomy 21 fetuses in later stages of pregnancy is of an order sufficient to explain the discrepancy between the higher numbers of trisomy 21 detected during amniotic fluid sampling than found at birth in women of 35 years and over. Perinatal mortality is known to be influenced by a large number of social, environmental, obstetric, and genetic factors. Chromosome abnormality forms an important component of the genetic factor but, to date, there is information only from four small surveys'-4 to show its contribution to perinatal deaths and late abortions, the main emphasis on the influence of chromosome abnormality in fetal was-tage and reproductive loss having been on early spontaneous abortions5 6 and on the live newborn.7 Paucity of data on chromosome anomalies in the later stages of pregnancy has been partly the result of the difficulty of getting material, and largely because the material presents problems in establishing cell growth. However, the need for such information has been emphasised8 because it may help to explain the apparent discrepancies between the higher number of chromosome abnormalities found in antenatal chromosome studies than expected from incidence figures from newborn data.9 10 Our survey of chromosome abnormalities in perinatal deaths and late abortions has been aimed at establishing an accurate picture of the frequency and pattern of chromosomal abnormalities in this group. In the present paper we report our results from a series of 500 cases