OBJECTIVE: Fetal sex prediction can be achieved using PCR targeted at the SRY 
gene by analyzing cell-free fetal DNA in maternal serum. Unfortunately, the 
results reported to date, show lack of sensitivity, especially in the first 
trimester of pregnancy. Therefore, determination of fetal sex by maternal serum 
analysis can not replace caryotype analysis following chorionic villus sampling.
PATIENTS AND METHODS: A new highly sensitive real-time PCR was developed to 
detect a SRY gene sequence in maternal serum. Analysis was performed on 121 
pregnant women during their first trimester of pregnancy (mean gestational age: 
11.8 weeks). Among them, 61 had at least one previous male-bearing pregnancy. 
Results were compared to fetal sex.
RESULTS: SRY PCR analysis of maternal serum was in complete concordance with 
fetal sex. Among the 121 pregnant women, 61 were bearing a male fetus and 60 a 
female fetus No false negative results were observed. Furthermore, no false 
positive results results occurred although 27 women carried female fetus during 
the current pregnancy, had at least one previous male-bearing pregnancy.
DISCUSSION AND CONCLUSION: This study demonstrates that a reliable, non-invasive 
sex determination can be achieved by PCR analysis of maternal serum during the 
first trimester of pregnancy. This non-invasive approach for fetal sex 
prediction should have great implications in the management of pregnant women 
carriers of an X-linked genetic disorder. Prenatal diagnosis is thus performed 
for male fetuses only, avoiding invasive procedures and the risk of fetal loss 
for female fetuses.