Perinatal characteristics of the phenotypically and chromosomally abnormal live-born.

Perinatal characteristics of 105 singleton live infants born during the last 5 years and suspected phenotypically of having karyotypic abnormalities were studied; 33 abnormal karyotypes were found. These pregnancies were compared with all pregnancies delivering at our hospital during the same time period. A retrospective analysis using our perinatal data base examined maternal age, gravidity, parity, race, mode of delivery, birth weight, gestational age at delivery, Apgar scores, and size for gestational age. Within the phenotypically abnormal group, karyotypically normal and abnormal infants showed no significant differences in primary cesarean rates, low Apgar scores, mean birth weight, or appropriateness of size for gestational age. Karyotypically abnormal infants were smaller than the general population (P less than .001) and had lower Apgar scores (P less than .05) but were just as likely to be full-term (66.7 versus 70.3%). These chromosomally abnormal pregnancies had a higher primary cesarean rate than the general population (30.3 versus 15.4%; P less than .001). Black infants undergoing genetic studies had a 37% rate of karyotypic abnormalities, which was significantly higher than the 12.5% rate in the white infants tested (P less than .05). The term black infant with phenotypic abnormalities suggestive of karyotypic abnormalities may be less likely to be recognized and appropriately tested. Increased awareness of phenotypic abnormalities with subsequent genetic testing seems warranted.