High incidence of emergency cesarean section among fetuses with unrecognized chromosomal abnormalities.

OBJECTIVE: To examine the incidence of obstetric complications in fetuses with unrecognized chromosomal anomalies compare with those in which the diagnosis was known before hand.
METHODS: All cases followed at a private facility in San Juan, PR during the time from January 1993 through February 1997 were evaluated in terms of gestational age and method of diagnosis and eventual pregnancy outcome.
RESULTS: There where 9 cases of chromosomal anomalies documented by karyotype analysis among 1377 (0.65%). Among this group, 5 cases were detected by a combination of maternal serum screening, analysis of risk factors and sonography. Among these, 3 cases elected pregnancy termination, one case of trisomy 21 was delivered stillborn vaginally at 32 weeks and one case of trisomy 18 delivered vaginally at 29 weeks. Among the 4 cases not recognized prenatally, one case of trisomy 21 was delivered at 27 weeks by classical cesarean section due to malpresentation and 3 cases (2 of trisomy 18 and one trisomy 21) where delivered by emergency transverse cesarean section due to suspected fetal hypoxia.
CONCLUSIONS: The very high frequency of emergency cesarean section (100%) among fetuses with unrecognized major chromosomal anomalies should make us increase our efforts to obtain at prenatal diagnosis. In all of these cases, a prior diagnosis would have probably avoided a cesarean section and the associated potential maternal morbidity. PRECIS: The high incidence of emergency cesarean section among fetuses with unrecognized chromosomal anomalies should make prenatal diagnosis of these conditions a primary goal.