Sonographic early fetal gender assignment: a longitudinal study in pregnancies after in vitro fertilization.

OBJECTIVES: A longitudinal evaluation by sonography of external genitalia in human embryos/early fetuses with a known time from fertilization is lacking. Our aim was to assign by sonographic evaluation of external genitalia the early fetal gender in a cohort of pregnancies after in vitro fertilization. Sonographic examinations were performed in each case in three subsequent sessions over a period of time early in gestation in order to establish a temporal threshold, expressed in terms of days from fertilization, at which absolute accuracy in gender prediction is achievable. METHODS: Thirty-two fetuses were included in this prospective longitudinal study. Each was examined three times for gender assignment. The first observation was performed between 65 and 69 days from fertilization, the second between 70 and 74 days and the third between 75 and 79 days. Transvaginal and/or transabdominal sonography was used to detect the 'sagittal sign' as a marker of fetal gender. The results of ultrasound examinations were compared with gender at birth or with karyotype obtained from amniotic fluid cells or chorionic villus sampling. RESULTS: Fetal gender assignment was feasible in 29 out of 32 fetuses (90%) at the first examination and in all cases at the second and third examinations. Fetal gender prediction was correct in 76% of cases in which fetal gender was assigned (22/29) at the first examination; accuracy for males was 46% (6/13) and for females 100% (16/16). At the second and third examinations, accuracy for gender prediction achieved 100% for both genders. Concerning the temporal threshold, absolute accuracy in gender prediction was achieved at 69 days from fertilization, corresponding to 11+6 weeks based on the last menstrual period. CONCLUSION: This study provides important information about the earliest stage, expressed in terms of days from fertilization, at which it is possible to make a certain diagnosis of fetal gender by sonography.

First-trimester fetal sex prediction by deoxyribonucleic acid analysis of maternal peripheral blood.

OBJECTIVES: We investigated whether the number of weeks of gestation influences the accuracy of first-trimester fetal sex prediction by analysis of deoxyribonucleic acid extracted from whole maternal blood. A comparison was also made to determine whether a difference exists between this approach and the deoxyribonucleic acid analysis of transcervical cells performed on the same group of subjects. STUDY DESIGN: Deoxyribonucleic acid was isolated from 50 maternal blood samples taken between gestational weeks 7 and 11. The sex of the fetus was assessed by nested polymerase chain reaction specific for the amelogenin gene. A receiver-operating characteristic curve analysis was used to correlate the accuracy of fetal gender prediction with the gestational age and also to compare the goodness of the 2 methods under investigation. RESULTS: Analysis of the receiver-operating characteristic curve provided a cutoff value of 9 weeks 4 days of gestation for both tests, indicating that a higher degree of accuracy in the sex assignment was obtained in those samples taken before or at this time. However, this difference was statistically significant only for analysis of deoxyribonucleic acid from maternal blood. The comparison between tests of deoxyribonucleic acid from maternal blood and from transcervical cells showed that the first approach is better, although a statistically significant difference was not found. CONCLUSION: Analysis of maternal blood deoxyribonucleic acid is a better approach than analysis of trans-cervical cell deoxyribonucleic acid in fetal sex prediction. The highest degree of accuracy is obtained when blood is drawn before 10 weeks of gestation. This can be important when sampling of chorionic villi should be avoided because of the risk of an X-linked disease when the fetal sex is female.

Biometrical threshold of biparietal diameter for certain fetal sex assignment by ultrasound.

OBJECTIVES: The aim of this study was to establish the biometric threshold of biparietal diameter (BPD), assumed to be an independent variable of gestational age, at which 100% accuracy in the assessment of fetal sex by ultrasonography is achievable. METHODS: Transvaginal and/or transabdominal sonography was used for detecting the 'sagittal sign' as a marker of fetal sex in 385 fetuses with BPD between 18 and 29 mm. The results of ultrasound examination were compared with sex at birth or with karyotype obtained from amniotic fluid cells or chorionic villus sampling. RESULTS: Fetal sex assignment was feasible in 337 of 385 cases (87.5%). Of the 312 fetuses with known fetal sex outcome, 164 were males and 148 were females. An accuracy rate of 100% was achieved when a BPD of > or = 23 mm was obtained. CONCLUSION: This study provides important information about the earliest stage of fetal development, expressed in terms of BPD, at which a diagnosis of fetal sex can be made with 100% accuracy.

Analysis of fetal sex in TCC sample DNA: a contribution to the validation of this approach.

We compared two methods of collection of transcervical cell samples, mucus aspiration and cytobrush, with respect to the efficiency in determining fetal sex and we correlated the results with the week of gestation (7-11 weeks) to evaluate if the age of gestation influenced the success of the analysis. DNA extracted from TCC samples recovered by mucus aspiration (n = 27) and cytobrush (n = 36) were analysed by nested PCR to predict fetal sex. The statistical indices of sensitivity, specificity, positive predictive value and negative predictive value were determined, and compared with those of other studies previously performed. No statistically significant difference was found between the two methods of TCC sampling concerning the success of fetal sex prediction which was high for both methods (78 per cent and 89 per cent) and no correlation with the week of gestation was found. Transcervical cell sampling represents an encouraging prospect for first-trimester prenatal diagnosis even when the least invasive techniques are used.