Ultrasonographic fetometry and determination of fetal sex in buffaloes (Bubalus bubalis)

The aim of the current study was to establish ultrasonic biometric threshold of different fetal parts in buffaloes and to evaluate the feasibility and accuracy of ultrasonic fetal sex determination. Serial ultrasonographic examinations were carried out on twelve pregnant buffalo-cows, during which fetal parts were measured, and fetal sex and presentation were determined. The obtained results revealed that embryo and amniotic vesicle (AV) were detected by the forth and fifth week of pregnancy, respectively. Organization was observed by the seventh week, while ossification was indicated between the eighth and 10th week. High correlations were found between different studied parameters and gestational age, where the highest correlation was found with the crown-rump length (CRL) and amniotic vesicle diameter (AVD) at the early-gestation; the biparietal diameter (BPD) at the mid-gestation; and the eyeball diameter (EBD) at the mid- and late-gestation. The results also revealed that the best window for fetal sexing was found between the 10th and 18th week of gestations, with an overall accuracy of 97.1%. The final polarity with all fetuses in anterior presentation was adopted by the 30th week. In conclusion, the overall data indicated the feasibility and value of ultrasonographic fetometry in buffaloes for evaluation of fetal development, estimation of gestational age and determination of fetal sex.     

Equine fetal sex determination using circulating cell-free fetal DNA (ccffDNA)

In this study, polymerase chain reaction (PCR) reamplification of the first PCR product (2nd-PCR) and a qPCR assay were used to detect the sex determining region Y (SRY) gene from circulating cell-free fetal DNA (ccffDNA) in blood plasma of pregnant mares to determine fetal sex. The ccffDNA was isolated from plasma of 20 Thoroughbred mares (5-13 y old) in the final 3 mo of pregnancy (fetal sex was verified after foaling). For controls, plasma from two non-pregnant mares and two virgin mares were used, in addition to the non-template control. The 182 bp nucleotide sequence corresponding to the SRY-PCR product was confirmed by DNA sequencing. Based on SRY/PCR, 8 of 11 male and 9 of 9 female fetuses were correctly identified, resulting in a sensitivity of 72.7% (for male fetuses) and an overall accuracy of 85%. Furthermore, using SRY/2nd-PCR and qPCR techniques, sensitivity and accuracy were 90.9 and 95%, respectively. In conclusion, this study is apparently the first report of fetal sex determination in mares using ccffDNA.     

Ultrasonographic assessment of early pregnancy diagnosis,fetometry and sex determination in goats

This study was conducted to use B-mode trans-rectal (TR) and trans-abdominal (TA) ultrasonography to determine early pregnancy and fetometry as crown-rump-length (CRL) and bi-parietal-diameter (BPD). A total of 110 does aged between 8 and 36 months were used. The accuracy for detecting early pregnancy (fetal fluids and heartbeats) and fetal number (single or twins) was measured. The relationship between gestation age and CRL or BPD was determined from day 40 to 109 of gestation. The accuracy of fetal sexing was determined by differentiation of genital tubercle (GT) at different stages of gestation (from day 40 to 109 of gestation). The examination revealed 95.5% of examined does were pregnant, with accuracy 100% in detecting pregnancy for positive cases. The fetal number was 45.7% and 54.3% for single and twins + triplets, respectively. The TR probe enabled the reliable and earlier recognition of fetal fluid and heartbeats (indicating pregnancy) than TA probe. For maximum reliability, the TR observation of heartbeats is recommended as conclusive evidence of the presence of a live fetus. The TA convex probe was used from day 40 to 89 for measuring CRL and from day 40 to 109 for measuring the BPD. Gestation equations were: CRL = 0.464x ? 17.767 and BPD = 0.055x ? 1.431 (x = gestational age in days). The relation between gestational age and CRL or BPD was highly (p < 0.0001) significant. The fetal sexing was found in 100, 83.3 and 64.3% of single pregnancies and in 85.7, 80 and 52.3% of twins + triplets pregnancies during 40–60 days, 61–70 days and 71–109 days of gestation, respectively. The accuracy of sex identification among the 3 groups was not significantly (p > 0.05) higher in single than twins + triplets pregnancies. However, identification of GT in male fetus was possible from day 40 onward. From a total of 105 scanned does, 80 (76.25) were sexed. In conclusion, B-mode real-time ultrasonography is recommended as a reliable mean for early detection of gestation as early as 19–27 days after mating, for CRL or BPD measuring as well as fetal sex determination from day 40 of gestation onwards under field conditions.     

Ultrasonographic fetometry and prenatal fetal sex assessment in camels (Camelus dromedarius)

The aims of this study were to determine the developmental patterns of some fetal parts to achieve a high accuracy level in the assessment of gestational age and to assess the feasibility and accuracy of ultrasonic prenatal fetal sex assessment in camels. Serial ultrasonographic examinations were carried out on seven pregnant dromedary camels. A total of 329 ultrasonographic examinations were conducted between the second and the 54th weeks of pregnancy. Intrauterine fluid accumulation was detected between the second and third weeks of pregnancy. The embryo proper was noticed between the third and fourth weeks. Organization of the embryo was first observed between the sixth and seventh weeks. Ossification was first detected between the seventh and ninth weeks. The accessibility during the total gestational period was 35/329 (10.6%) for crown-rump length, 35/329 (10.6%) for biparietal diameter, 42/329 (12.8%) for abdominal diameter, 42/329 (12.8%) for ruminal length, and 126/329 (38.3%) for eyeball diameter. A high correlation was found between gestational age and each of the studied parameters (P < 0.0001). The highest correlation was found with the crown-rump length and the biparietal diameter during the first trimester and with the eyeball diameter during the third trimester of pregnancy. The overall accuracy of the ultrasonic prenatal fetal sex assessment was 91.7%. The best window was found during the 11th week of pregnancy. It was concluded that sonographic fetometry can be useful for the evaluation of fetal development, the estimation of gestational age, and the prediction of prenatal fetal sex in camels.     

Ultrasonographic estimation of fetal weight--residents accuracy

The aim of this retrospective study was to evaluate the accuracy of gynecology and obstetrics residents when performing ultrasonographic estimation of fetal weight. The total of 400 ultrasonographic estimations of fetal weight and corresponding neonatal weight were collected and divided into 3 groups according to physicians' experience (junior and senior residents, staff physicians). The accuracy of fetal weight estimation correlated positively with the level of physicians'experience. The proportional difference between ultrasound estimation and actual birth weight varied from 8.45% to 6.88% (junior residents 8.45%, senior residents 6.95%, staff physicians 6.88%). The proportion of ultrasonograhic estimates that fell within 10% of birth weight varied from 59.09% to 79.21% (junior residents 59.09%, senior residents 78.44%, staff physicians 79.21%). Senior residents reach a highly acceptable accuracy in ultrasonographic estimation of fetal weight which is comparable to staff physicians.     

Ultrasonographic visualization of the fetal eye

This paper describes the analysis of the fetal eye in utero using ultrasonography. Such analysis has allowed the diagnosis of two cases of cyclopia and one case of microphthalmia. Two of the three pregnancies of a woman affected by autosomal dominant aniridia were found to be normal at 17 weeks of gestation and at birth; her oldest daughter was affected. The motility of the eyes was also noted when the fetus was examined. No movement or rapid and slow movements are seen more frequently as the fetus progresses through pregnancy. The centiles for the intermalar and interethmoidal distances are described for fetuses between weeks 10 and 40 of gestation. This system should be used with caution because of the difficulties in interpreting views of the fetal eye.     

Equine fetal sex determination using a single ultrasonic examination under farm conditions

The aims of this study were to evaluate the reliability, under general farm conditions, of the use of a single transrectal sonogram in pregnant mares to determine fetal sex by locating the genital tubercle, and the feasibility of extending the period of gestation in which this examination can be carried out. This research was done during routine reproductive examinations on three different stud farms. Forty mares between the 54th and the 89th day of gestation were examined once; gestation was calculated by identifying the last day of mating as Day 0. In order to verify the precision of the determination, data regarding the sex of the foals at birth were collected. This information was not available for two of the 40 mares examined. The diagnosis was made without any certainty level or any other methods which might quantify or increase the reliability of the examination. Of 40 mares, a diagnosis was possible in 35 (87%); in five mares (12%), it was not possible due to insufficient data. Twenty-six of 40 sex determinations (65%) were correct, 9 of 40 (22%) were incorrect. The comparison of the percentages obtained using the chi2-test was P = 0.0011. In spite of positive statistical analysis, the results of this study are not sufficient to allow systematic use of this approach due to the high percentage of error.     

Alternative strategies of fetal sex diagnoses and sex preselection

Abstract

Motives for sex control include avoidance of sex‐linked disease and realization of preferred sex compositions of children. Currently, the only wholly effective means of sex control is diagnosis of fetal sex by mid‐trimester karyotyping of amniotic fluid cells followed by corrective abortion when diagnosis is adverse. Unfortunately the delays involved in karyotyping mean that abortion cannot be minimum‐risk suction curretage. Radioimmunoassay procedures allow somewhat earlier diagnosis and therefore less risky abortion, but entail more diagnostic error. In the first part of the paper, several assay procedures are evaluated in terms of relative expense as compared to karyotyping, gestational age when reliability is highest, and level of that reliability. Later portions of the paper focus on use of radioimmunoassay to diagnose fetal sex for purposes of regulating the sex composition of offspring. Three strategies are compared with respect to their efficiency and expected levels of diagnosis and abortion.     

Cattle fetal sex determination by polymerase chain reaction using DNA isolated from maternal plasma

The objective of this study was to evaluate the use of polymerase chain reaction analysis (PCR) of fetal cells/DNA in the maternal plasma of pregnant cows to determine the sex of the fetus. Plasma was harvested from 35 cows of mixed genotype at different stages of pregnancy ranging from 5 to 35 weeks. A male calf and a heifer calf provided the control samples. Fetal sex was determined by amplification of Y-specific sequences. For the 35 cows, the fetal sex predicted by this technique was in accordance with the sex of the calf at birth in 88.6% of cases. The agreement between predicted and observed fetal sex was less for cows with a gestational length of 35-48 days (63.6%). Regression analysis showed that there was a strong relationship between the probability of correctly predicting fetal sex and the stage of gestation. It was estimated that the test performed at 43.8 days post fertilization would have 95% accuracy, increasing to 99% accuracy for testing at 48.4 days and 99.9% accuracy for tests at 55.0 days or later. It was concluded that PCR analysis of fetal cells in maternal plasma can be used to predict successfully the sex of the fetus in cattle.     

Plant sex determination and sex chromosomes

Sex determination systems in plants have evolved many times from hermaphroditic ancestors (including monoecious plants with separate male and female flowers on the same individual), and sex chromosome systems have arisen several times in flowering plant evolution. Consistent with theoretical models for the evolutionary transition from hermaphroditism to monoecy, multiple sex determining genes are involved, including male-sterility and female-sterility factors. The requirement that recombination should be rare between these different loci is probably the chief reason for the genetic degeneration of Y chromosomes. Theories for Y chromosome degeneration are reviewed in the light of recent results from genes on plant sex chromosomes.     

Bird sex determination

During the evolution, sex determination occurred early. Sex determining factors were progressively isolated from other genes in sexual chromosomes, or gonosomes. Among vertebrates, evolution took two opposite pathways : in mammals, the system of XX:XY sex determination, with Y chromosome, induces male differentiation. In contrast, in birds, the system ZZ:ZW, with the W chromosome, induces female differentiation. But comparative studies show that the two pathways are not so simple. In the chicken as in the lower vertebrates, estrogens play a central role in gonadal sex differentiation. Several genes, show to be critical for mammalian determination, are also expressed in the chicken but their expression pattern differs, indicating functional plasticity. The W-linked female determinants remains still unknown. But comparative studies of the two pathways, with conserved and divergent elements, are broadening our understanding of sex determination.     

Maternal testosterone and fetal sex

To investigate the influence of fetal sex on maternal testosterone levels throughout pregnancy, blood was sampled from 37 healthy pregnant women from week 14 until term and at 6 weeks postpartum. Testosterone concentrations were measured with a highly specific RIA after chromatographic purification. Mean (+/- SD) testosterone at the end of gestation was significantly higher compared to non-pregnant values (3.10 +/- 2.38 mM/l, n = 32 vs 1.14 +/- 1.06 nM/l, n = 35). It appeared that in women carrying a male fetus testosterone levels gradually increased during pregnancy up to 3.99 +/- 2.72 nM/l. In women carrying a female fetus the levels decreased after the first trimester from 2.44 nM/l to 1.80 nM/l. A statistically significant difference (P less than 0.01) existed in maternal testosterone concentrations between both groups during the second half of pregnancy.     

Germ cell sex determination

Whether a germ cell embarks on oogenesis, the female gametogenic pathway, or spermatogenesis, the male pathway, may be determined cell-autonomously, by the germ cell's own genes, or by the tissue environment in which it is located. The decision may or may not be associated with the time of entry into meiosis, and this in turn may be controlled wholly by the germ cell's own genes, or in part by the environment. These issues will be explored with reference to Caenorhabditis elegans, Drosophila and the mouse.     

Multilocus autosomal sex determination

The two basic one locus sex determination models, diploid individual sex determination and parental sex determination, are generalized to the multilocus framework. As in the single locus case, it is established that there are two classes of polymorphic equilibria, equilibria with even sex ratio and equilibria with equal allele frequencies in the two sexes. The condition for external stability of this second class equilibria to invasion by a new mutant allele is that a new appropriately averaged sex ratio near the equilibrium be moved closer to the even sex ratio. However, stable polymorphisms with noneven sex ratio are not those that have a sex ratio as close as possible to 1/2, in contrast to the single locus case.Research supported in part by NIH grants GM 28016 and GM 10452 and a grant from the U.S.-Israel Binational Science Foundation