Polymerase-chain-reaction-based detection of fetal rhesus D and Y-chromosome-specific DNA in the whole blood of pregnant women during different trimesters of pregnancy.

OBJECTIVE: The aim of this study was to determine whether or not a noninvasive procedure utilizing maternal peripheral blood as the source of DNA and polymerase chain reaction (PCR) could be used to detect fetal rhesus D (RhD) status as well as fetal gender during different gestational stages of pregnancy. MATERIALS AND METHODS: Maternal blood samples were obtained from 54 RhD-negative pregnant women during the first trimester (6-13 weeks, n = 14), second trimester (14-26 weeks, n = 26) and third trimester (27-40 weeks, n = 14). Genomic DNA was extracted from the whole blood and analyzed by seminested and nested PCR for detection of DNA sequences corresponding to RhD (n = 54) and Y chromosome (n = 48) using RhD and Y-chromosome-specific oligonucleotide primers, respectively. The seminested/nested PCR results were compared with the RhD status and gender of the babies after delivery. RESULTS: The sensitivity and specificity of seminested PCR for detection of fetal RhD positivity in whole blood of pregnant women were 81 and 100%, respectively, while the sensitivity and specificity of nested PCR for detection of male fetuses, using Y-chromosome-specific DNA as a marker, were 96 and 91%, respectively. There were no significant differences in the PCR results with samples obtained from women at different gestational stages of pregnancy. CONCLUSION: Seminested and nested PCRs for detection of fetal RhD and gender status, respectively, by using the blood of pregnant women during different gestational stages of pregnancy, are reliable noninvasive procedures with high sensitivity and specificity.

Effect of repeated doses of dexamethasone on the incidence and severity of respiratory distress syndrome in multifetal gestation between 24 and 34 weeks.

The objective of the study was to evaluate the effects of antenatal corticosteroid therapy in multiple pregnancy on the incidence and severity of respiratory distress syndrome (RDS). Twenty-two women with twin, 12 with triplet and 2 with quadruplet pregnancies and an emergency group of 20 mothers with twin pregnancies, who only had one course of dexamethasone, were compared with controls. Corticosteroid therapy was associated with a reduction in moderate to severe RDS in all groups (twins p < 0.01, triplets and quadruplets p < 0.008) and the emergency group with dexamethasone therapy (p < 0.036) when compared to their individual controls. Dexamethasone reduced the duration of stay in the neonatal intensive care unit of the emergency twin group (p < 0.01). Neonatal birth weights were significantly less in all groups treated with repeated doses in comparison to the controls.

Detection of Y chromosome-specific DNA in the plasma and urine of pregnant women using nested polymerase chain reaction.

The present study was undertaken to evaluate a nested polymerase chain reaction (PCR) for detection of Y chromosome-specific fetal DNA in maternal plasma and urine of pregnant women during different gestational stages. DNA isolated from plasma and urine samples of 80 pregnant women (between 7 and 40 weeks' gestation) underwent amplification for Y chromosome-specific 198 bp DNA by nested PCR. The postpartum analysis of fetal gender showed that 55 women carried male and 25 female fetuses. Among the 55 women bearing male fetuses, Y chromosome-specific signals were detected in 53 (96%) plasma and 21 (38%) urine samples. Moreover, out of 25 women bearing female fetuses, 3 (12%) and 1 (4%) women had Y chromosome-specific signal in plasma and urine, respectively. Analysis of results with respect to gestational age revealed that there was no significant difference in the detection of Y chromosome-specific DNA between different trimesters in maternal plasma of women bearing male fetuses. These results showed that fetus-specific DNA was detected with high sensitivity (96%) and specificity (88%) in the maternal plasma by nested PCR, and therefore the method could be useful as a non-invasive procedure for fetal sex determination and prenatal diagnosis.