Fetal gender screening by ultrasound at 11 to 13+6weeks

Imaging in fetal genital anomalies

Genital anomalies are a heterogeneous group of congenital pathologies that have become increasingly relevant since the Chicago Consensus of 2005. Their postnatal diagnosis has developed significantly in the last two decades, while prenatal diagnosis seems to be underdeveloped, with few protocols available, fragmented scientific literature, and low diagnostic rates. This review aims to examine the current status of this subspecialty from the perspective of prenatal imaging. Indications for the evaluation of fetal genitalia can be divided into medical and non-medical reasons. Medical reasons include sex-linked disorders, detection of other anomalies, relevant family history, or multiple pregnancy. Non-medical reasons include parental request for sex disclosure. Disclosure of fetal sex may be associated with ethical, legal, and medical issues. The main imaging technology used is 2D ultrasound, although there are other complementary techniques such as 3D, MRI, or Color Doppler. Regarding working methodology, several authors have drawn attention to the lack of standardized protocols and guidelines. Most guidelines tend to limit their recommendations to study indications and ethical issues. Technical proposals, measurements, or working methods have not yet been standardized. Fetal sex determination is usually divided into early and late gestation. Early gestation is based on the sagittal sign. Late gestation is based on direct visualization. There are several measurements to describe male and female genitalia, such as penile length, bilabial diameter, or scrotal diameter. Prenatal diagnosis of genital pathologies presents some particularities such as the wide spectrum of phenotypes, the high frequency of associated deformities, or the time of diagnosis. Some of the most frequent pathologies are ambiguous genitalia, fetal sex discordance, hypospadias, micropenis, clitoromegaly, ovarian cysts, hydro(metro)colpos, and cloacal anomalies. Higher-quality studies and direction from scientific societies through the implementation of clinical guidelines are needed.

PFP-LHCINCA: Pyramidal Fixed-Size Patch-Based Feature Extraction and Chi-Square Iterative Neighborhood Component Analysis for Automated Fetal Sex Classification on Ultrasound Images

Objectives

Fetal sex determination with ultrasound (US) examination is indicated in pregnancies at risk of X-linked genetic disorders or ambiguous genitalia. However, misdiagnoses often arise due to operator inexperience and technical difficulties while acquiring diagnostic images. We aimed to develop an efficient automated US-based fetal sex classification model that can facilitate efficient screening and reduce misclassification.

Methods

We have developed a novel feature engineering model termed PFP-LHCINCA that employs pyramidal fixed-size patch generation with average pooling-based image decomposition, handcrafted feature extraction based on local phase quantization (LPQ), and histogram of oriented gradients (HOG) to extract directional and textural features and used Chi-square iterative neighborhood component analysis feature selection (CINCA), which iteratively selects the most informative feature vector for each image that minimizes calculated feature parameter-derived k-nearest neighbor-based misclassification rates. The model was trained and tested on a sizeable expert-labeled dataset comprising 339 males' and 332 females' fetal US images. One transverse fetal US image per subject zoomed to the genital area and standardized to 256 × 256 size was used for analysis. Fetal sex was annotated by experts on US images and confirmed postnatally.

Results

Standard model performance metrics were compared using five shallow classifiers-k-nearest neighbor (kNN), decision tree, naïve Bayes, linear discriminant, and support vector machine (SVM)-with the hyperparameters tuned using a Bayesian optimizer. The PFP-LHCINCA model achieved a sex classification accuracy of ≥88% with all five classifiers and the best accuracy rates (>98%) with kNN and SVM classifiers.

Conclusions

US-based fetal sex classification is feasible and accurate using the presented PFP-LHCINCA model. The salutary results support its clinical use for fetal US image screening for sex classification. The model architecture can be modified into deep learning models for training larger datasets.

First trimester determination of fetal gender by ultrasonographic measurement of anogenital distance: A cross-sectional study

Background

In some patients with a family history of the gender-linked disease, determination of the fetal gender in the first trimester of pregnancy is of importance. In X-linked recessive inherited diseases, only the male embryos are involved, while in some conditions, such as congenital adrenal hyperplasia, female embryos are affected; hence early determination of fetal gender is important.

Objective

The aim of the current study was to predict the gender of the fetus based on the accurate measurement of the fetal anogenital distance (AGD) by ultrasound in the first trimester.

Materials and Methods

To determine the AGD and crown-rump length in this cross-sectional study, 316 women with singleton pregnancies were exposed to ultrasonography. The results were then compared with definitive gender of the embryos after birth.

Results

The best cut-off for 11 wk to 11 wk, 6 days of pregnancy was 4.5 mm, for 12 wk to 12 wk, 6 days was 4.9 mm, and for 13 wk to 13 wk, 6 days was 4.8 mm.

Conclusion

AGD is helpful as an ultrasonographic marker that can determine fetal gender in the first trimester, especially after 12 wks.

Pitfalls in assessing chorioamnionicity: novel observations and literature review

Accurate diagnosis of chorioamnionicity in multiple pregnancies is the key to appropriate clinical management of multiple gestation. Although prenatal ultrasound assessment of chorioamnionicity is well established and highly accurate if performed in early pregnancy, exceptions and artifacts arise from anatomic variations in multiple pregnancies and unusual sonographic features do exist. We have summarized our own experiences and reports from the literature on these pitfalls as follows: (1) discordant fetal sex in monochorionic pregnancies due to sex chromosome abnormalities, genital malformation in 1 fetus, or dizygotic twins forming a monochorionic placenta; (2) separate placental masses in monochorionic pregnancies due to bipartite placenta; (3) false-negative and false-positive λ sign can arise for various reasons, and in partial monochorionic/dichorionic placentas both T and λ sign may co-exist; (4) intrauterine synechia appearing as a thick and echogenic intrauterine septum may lead to erroneous diagnosis of dichorionic twins; and (5) errors in ascertaining amnionicity by the visualization of thin intertwin amniotic membranes and the number of yolk sacs. The ultrasound techniques to reduce inaccuracy in prenatal determination of chorioamnionicity and the use of single nucleotide polymorphisms based on noninvasive prenatal test to determine zygosity are also reviewed.

Accuracy of fetal sex determination in the first trimester of pregnancy using 3D virtual reality ultrasound

PURPOSE

Early detection of fetal sex is becoming more popular. The aim of this study was to evaluate the accuracy of fetal sex determination in the first trimester, using 3D virtual reality.

METHODS

Three-dimensional (3D) US volumes were obtained in 112 pregnancies between 9 and 13 weeks of gestational age. They were offline projected as a hologram in the BARCO I-Space and subsequently the genital tubercle angle was measured. Separately, the 3D US aspect of the genitalia was examined for having a male or female appearance.

RESULTS

Although a significant difference in genital tubercle angles was found between male and female fetuses, it did not result in a reliable prediction of fetal gender. Correct sex prediction based on first trimester genital appearance was at best 56%.

CONCLUSION

Our results indicate that accurate determination of the fetal sex in the first trimester of pregnancy is not possible, even using an advanced 3D US technique.

The ultrasound identification of fetal gender at the gestational age of 11-12 weeks

Introduction

The early prenatal identification of fetal gender is of great importance. Accurate prenatal identification is currently only possible through invasive procedures. The present study was conducted to determine the accuracy and sensitivity of ultrasound fetal gender identification.

Materials and Methods

The present cross-sectional study was conducted on 150 women in their 11^th and 12^th weeks of pregnancy in Hamadan in 2014. Ultrasound imaging performed in the 11^th and 12^th weeks of pregnancy for fetal gender identification identified the fetus either as a girl, a boy, or as a "gender not assigned." Frequency, sensitivity, specificity, positive and negative predictive values, and accuracy of the gender identification was assessed using SPSS version 20. The significant level was 0.05 in all analyses.

Results

Of the total of 150 women, the gender was identified as female in 32 (21.3%), as male in 65 (43.3%), and not assigned in 53 (35.3%); overall, gender identification was made in 64.6% of the cases. A total of 57 male fetuses were correctly identified as boys, and 8 female fetuses were wrongly identified as boys. As for the female fetuses, 31 were correctly identified as girls, and 1 was wrongly identified as a boy. The positive predictive value for the ultrasound imaging gender identification was 87.6% for the male fetuses and 96.8% for the female fetuses.

Conclusion

The present study had a much higher gender identification accuracy compared to other studies. The final success of fetal gender identification was about 91% in the 11^th and 12^th weeks of pregnancy.

First-trimester determination of fetal gender by ultrasound: measurement of the ano-genital distance

INTRODUCTION

Early ultrasound fetal sex determination is of obvious interest, particularly in the context of X-linked diseases. In the human, the anogenital distance, i.e., the distance between the caudal end and the base of the genital tubercule is sexually dimorphic. This difference is apparent from 11 weeks of gestation. The aim of this prospective study was to evaluate the accuracy of anogenital distance measurement during the first trimester ultrasound in the early determination of fetal gender.

MATERIALS AND METHODS

Fetal gender was assessed by ultrasound in 310 singleton pregnancies at 11-14 weeks of gestation. The optimal cut-off was determined by the minimal p-value technic and validated using bootstrap simulation.

RESULTS

310 women were included. A cut-off of 4.8mm was determined to predict male (≥4.8mm) or female (<4.8mm) fetuses. Sex was correctly determined for 87% of the males and 89% of the females. The inter-observer variability was excellent.

CONCLUSION

This study presents a new sonographic sign for early fetal sex determination that has not been previously explored. It appears to be an accurate tool but it requires further validation in larger series.

Accuracy of fetal sex determination on ultrasound examination in the first trimester of pregnancy

PURPOSE

The aim of this study was to evaluate the feasibility and success rate of sex determination on transabdominal sonographic examination at 11-13 weeks' gestation and to identify factors influencing accuracy.

METHODS

In this prospective observational evaluation of 672 fetuses between 11 weeks' and 13 weeks + 6 days' gestational age (GA), we determined fetal sex according to the angle of the genital tubercle viewed on the midsagittal plane. We also analyzed maternal, fetal, and operator factors possibly influencing the accuracy of the determination.

RESULTS

Fetal sex determination was feasible in 608 of the 672 fetuses (90.5%), and the prediction was correct in 532 of those 608 cases (87.5%). Fetal sex was more accurately predicted as the fetal crown-rump length (CRL), and GA increased and was less accurately predicted as the maternal body mass index increased. A CRL greater than 55.7 mm, a GA more than 12 weeks + 2 days, and a body mass index below 23.8 were identified as the best cutoff values for sex prediction. None of the other analyzed factors influenced the feasibility or accuracy of sex determination.

CONCLUSIONS

The sex of a fetus can be accurately determined on sonographic examination in the first trimester of pregnancy; the accuracy of this prediction is influenced by the fetal CRL and GA and by the maternal body mass index. © 2015 Wiley Periodicals, Inc. J Clin Ultrasound 44:272-277, 2016.

Accuracy of sonographic fetal gender determination: predictions made by sonographers during routine obstetric ultrasound scans

Objectives: The purpose of this study was to determine the accuracy of sonographer predictions of fetal gender during routine ultrasounds. Primarily, the study sought to investigate the accuracy of predictions made in the first trimester, as requests from parents wanting to know the gender of their fetus at this early scan are becoming increasingly common. Second and third trimester fetuses were included in the study to confirm the accuracy of later predictions. In addition, the mother's decision to know the gender was recorded to determine the prevalence of women wanting prenatal predictions. Methods: A prospective, cross sectional study was conducted in a specialist private obstetric practice in the Illawarra, NSW. A total of 640 fetuses across three trimesters were examined collectively by seven sonographers. Fetal gender was predicted using the sagittal plane only in the first trimester and either the sagittal or transverse plane in later trimesters. Phenotypic gender confirmation was obtained from hospital records or direct telephone contact with women postnatally.

Results: Results confirmed 100% accuracy in predictions made after 14 weeks gestation. The overall success rate in the first trimester group (11–14 weeks) was 75%. When excluding those scans where a prediction could not be made, success rates increased to 91%. Results were less accurate for fetuses younger than 12 weeks, with an overall success rate of 54%. Male fetuses under 13 weeks were more likely to have gender incorrectly or unable to be assigned. After 13 weeks, success rates for correctly predicting males exceeded that of female fetuses. Statistical differences were noted in the success rates of individual sonographers. Sixty seven percent of women were in favour of knowing fetal gender from ultrasound. Publicly insured women were more likely to request gender disclosure than privately insured women.

Conclusions: Sonographic gender determination provides high success rates in the first trimester. Results vary depending on sonographer experience, fetal age and fetal gender. Practice guidelines regarding gender disclosure should be developed. Predictions prior to 12 weeks should be discouraged.

The accuracy of 2D ultrasound prenatal sex determination

Background:

Pregnant women have been curious about the sex of their unborn child. The advent of ultrasound, its application into medicine, and the revolutionary changes in its resolution and function has led to the ability to assign a sex to these unborn children, thereby allaying the anxiety of these women but with consequent emergent ethical, moral, psycho-social, and medico-legal issues. The objectives were to determine the accuracy of sonographic prenatal sex determination, perform binary classification test, and the impact it has, including mis-diagnosis.

Materials and Methods:

A prospective prenatal sonographic sex determination study on 205 consecutive consenting pregnant women aged 20-40 years in a private hospital in Benin between August 2010 and October 2011. Questionnaires were administered to these women before and after the scan and the women were told the sex of the fetuses and their feelings on the determined sex recorded. The sex at birth was confirmed and compared to the scan determined gender by their case note and telephone. Relevant discussions during the scan and later on were recorded on the questionnaires. The statistical package used was SPSS version 17 and binary classification tests were performed.

Results:

The sensitivity (98.2%) and binary classification components values of prenatal sex determination were high with the sensitivity of detecting a female higher than that of males. Two males were misdiagnosed as females. Most of the women were happy even when the sex differed from that which they desired.

Conclusion:

Prenatal sonographic sex determination has a high sensitivity index. Consequently we advocate its use prior to more invasive sex tests.

Early fetal anatomical sonography

Over the past decade, prenatal screening and diagnosis has moved from the second into the first trimester, with aneuploidy screening becoming both feasible and effective. With vast improvements in ultrasound technology, sonologists can now image the fetus in greater detail at all gestational ages. In the hands of experienced sonographers, anatomic surveys between 11 and 14 weeks can be carried out with good visualisation rates of many structures. It is important to be familiar with the normal development of the embryo and fetus, and to be aware of the major anatomical landmarks whose absence or presence may be deemed normal or abnormal depending on the gestational age. Some structural abnormalities will nearly always be detected, some will never be and some are potentially detectable depending on a number of factors.

Incidental prenatal diagnosis of sex chromosome aneuploidies: health, behavior, and fertility

Objective. To assess the diagnostic relevance of incidental prenatal findings of sex chromosome aneuploidies. Methods. We searched with medical subject headings (MeSHs) and keywords in Medline and the Cochrane Library and systematically screened publications on postnatally diagnosed sex chromosomal aneuploidies from 2006 to 2011 as well as publications on incidentally prenatally diagnosed sex chromosomal aneuploidies from 1980 to 2011. Results. Postnatally diagnosed sex chromosomal aneuploidies demonstrated three clinical relevant domains of abnormality: physical (22-100%), behavior (0-56%), and reproductive health (47-100%), while incidentally prenatally diagnosed sex chromosomal aneuploidies demonstrated, respectively, 0-33%, 0-40%, and 0-36%. Conclusion. In the literature incidental prenatal diagnosis of sex chromosomal aneuploidies is associated with normal to mildly affected phenotypes. This contrasts sharply with those of postnatally diagnosed sex chromosomal aneuploidies and highlights the importance of this ascertainment bias towards the prognostic value of diagnosis of fetal sex chromosomal aneuploidies. This observation should be taken into account, especially when considering excluding the sex chromosomes in invasive prenatal testing using Rapid Aneuploidy Detection.

Accuracy of fetal gender determination in the first trimester using three-dimensional ultrasound

OBJECTIVES

To evaluate the accuracy of three-dimensional (3D) ultrasound in fetal gender assignment in the first trimester.

METHODS

A series of pregnant women attending at 11 to 13 + 6 weeks for the nuchal translucency (NT) scan were enrolled into the study. An ultrasound volume of each fetus was obtained and stored for offline analysis. On the reconstructed mid-sagittal plane, the angle between the genital tubercle and an imaginary line passing tangentially through the fetal back (genital angle) was estimated and a receiver-operating characteristics (ROC) curve was constructed to determine the best cut-off for genital angle in fetal male gender determination. Fetal gender was subsequently ascertained in all cases. To calculate the interobserver variability, a second operator repeated the measurements.

RESULTS

There were 85 cases included in the study. The genital angle in males was significantly higher than that in females (51.2 ± 11.3° (n = 36) vs. 18.9 ± 4.1 (n = 49), P < 0.001). The ROC curve revealed the estimated genital angle to have a high degree of accuracy in fetal gender determination (area under the curve ± SE = 1.000 ± 0.001). The best cut-off for male gender determination was found to be between 27° and 29° (sensitivity, 100%; specificity, 98.0%). There was a high degree of correlation between the two operators (r(2) = 0.998; coefficient of variation = 5.4%).

CONCLUSIONS

3D ultrasound is a highly accurate and reproducible tool for fetal gender assignment prior to 14 weeks of gestation.

Influence of maternal body mass index and gestational age on accuracy of first trimester gender assignment

OBJECTIVE

To determine the influence of maternal body mass index (BMI) and gestational age on the accuracy of image acquisition, first trimester fetal gender determination, and correct assignment.

METHODS

Women presenting for first trimester aneuploidy risk assessment at 11(0) to 13(6) weeks were prospectively enrolled. A mid-sagittal view of the fetus including the genital tubercle was obtained. The angle of the genital tubercle was measured with male assigned for angle >30°, female <10°, and indeterminate if 10-30°. This was compared with gender at birth. The influence of maternal and pregnancy characteristics on both image acquisition and correct gender assignment were evaluated.

RESULTS

A total of 256 women with 260 fetuses undergoing first trimester risk assessment were enrolled. The genital tubercle was identified in 247/260 (95%) of cases. Image acquisition was negatively influenced by increasing maternal BMI and early gestational age (34.8 ± 7.7 vs. 27.0 ± 6.1 kg/m(2), p < 0.0001 and 12.3 ± 0.5 vs. 12.6 ± 0.5 weeks, p = 0.02). Gender was assigned in 93.1% and correctly matched in 85.8% of fetuses. Positive predictive value (PPV) for male and female fetuses were 88.9% and 79.8%, respectively. Correct gender assignment was more likely in male compared with female fetuses (91.4 vs. 80.5%, p = 0.02).

CONCLUSION

Increasing maternal BMI negatively influences image acquisition during the first trimester for gender determination, but does not decrease the accuracy of correct gender assignment if the image is obtained.

Fetal sex determination using circulating cell-free fetal DNA (ccffDNA) at 11 to 13 weeks of gestation

OBJECTIVE

To examine the performance of a mass spectrometry-based detection platform using three Y-chromosome sequences for fetal sex determination from circulating cell-free fetal DNA (ccffDNA) in maternal blood in the first trimester of pregnancy.

METHODS

We extracted ccffDNA for the determination of fetal sex from stored maternal plasma obtained at 11 to 13 weeks' gestation from singleton pregnancies with documented fetal gender. Mass spectrometry was used to examine 236 specimens for the presence of three Y-chromosome sequences (SRY, DBY and TTTY2). The sample was classified as male, female or inconclusive depending on the detection of three, one/none and two sequences, respectively.

RESULTS

Three (1.3%) of the 236 cases were classified as invalid due to the absence of a well-defined spectral peak for TGIF and 22 (9.3%) were reported as inconclusive. In the 211 cases with a valid result, the fetal sex was correctly identified in 90 of 91 male babies and 119 of 120 female babies giving an accuracy of 99.1% and sensitivity and specificity for prediction of male fetuses of 98.9 and 99.2%, respectively.

CONCLUSION

Fetal sex determination can be accurately determined from maternal ccffDNA in the first trimester of pregnancy using mass spectrometry analysis.

Fetal sex determination: obstetricians' attitudes in antenatal screening units in Finland

AIM

To study obstetricians' attitudes in Finnish antenatal screening units concerning fetal sex determination without medical indication.

METHODS

A structured questionnaire to all delivery units (n = 37) and the main outpatient screening units (n = 18) in the country.

RESULTS

The majority of units made fetal sex determination without medical indication at patient's request during the second-trimester ultrasonographic screening. This examination was seen to have consequences for maternal-fetal attachment, but it was also considered medically useless and sometimes harmful. Only three out of the responding 32 units maintained quality control of the examination. A false diagnosis resulted extremely seldom in any litigation process.

CONCLUSIONS

More precise guidelines are needed for fetal sex determination in healthcare organisation.

Profile of Women Seeking Fetal Gender at Ultrasound in a Nigerian Obstetric Population

Objective: To determine the proportion of women that wanted to know fetal gender at ultrasound, characterize them and document reasons for wanting to know fetal gender.

Methodology: A cross-sectional study on consecutive pregnant women at 20 weeks or more gestation that presented for prenatal ultrasound at a private hospital in Nigeria from May to December 2005.

Results: Of the 1135 women, 167 (14·7%) sought to know the fetal gender. Significant independent factors included ethnic group, as women from the predominant Hausa–Fulani were less likely when compared to those of other ethnic groups (OR: 0·4, 95% CI: 0·2–0·7). Women with tertiary education were 6·6 times (OR: 6·6, 95% CI: 3·3–13·2) more likely. Women with a previous male baby were 30·6 times more likely (OR: 30·6, 95% CI: 13·6–68·5), while those with previous female baby were 54·3 times more likely (OR: 54·3; 95% CI: 23·4–125·8) to seek fetal gender. Main reasons for seeking fetal gender were preference for a particular fetal gender (57%); what wears to buy for the baby (24%) and curiosity (18%).

Conclusion: About 15% of the study group requested to know fetal gender and it was associated with ethnic group, maternal educational level and gender of the previous baby. The most common reason for wanting to know fetal gender was the desire for a particular gender.