Preconception sex selection for non-medical reasons:a representative survey from Germany

BACKGROUND: Preconception sex selection for non-medical reasons raises serious moral, legal and social issues. The main concern is based on the assumption that a freely available service for sex selection will distort the natural sex ratio and lead to a severe gender imbalance. However, for a severe gender imbalance to happen, at least two conditions have to be met. First, there must be a significant preference for children of a particular sex, and second, there must be a considerable demand for preconception sex selection. To ascertain whether or not these two conditions are met, we have conducted a survey in Germany. METHODS: As a representative sample of the German population, 1094 men and women aged 18-45 years were asked about their gender preferences and whether or not they could imagine selecting the sex of their children through flow cytometric separation of X- and Y-bearing sperm followed by intrauterine insemination. RESULTS: 58% of respondents stated that they do not care about the sex of their offspring. 30% wish to have a family with an equal number of boys and girls. 4% would like to have more boys than girls, 3% more girls than boys, 1% only boys and 1% only girls. For first-borns, however, there is still a preference for boys over girls. While 75.6% claimed to have no gender preference, 14.2% would like their first child to be a boy and 10.1% would like their first child to be a girl. Whereas 6% could imagine taking advantage of preconception sex selection, 92% found this to be out of the question. Even in the hypothetical case that a medication for sex selection were ever to become available, 90% stated that they would not want to use it. CONCLUSION: Given that a majority does not seem to care about the sex of their offspring and only a minority seem to be willing to select the sex of their children, a freely available service for preconception sex selection for non-medical reasons is rather unlikely to cause a severe gender imbalance in Germany.     

Ethics and society: Social aspects of >800 couples coming forward for gender selection of their children

The social characteristics of 809 couples attending a sex preselectionclinic have been studied. Their ethnic origins were: Indian57.8%, European 32.0%, Chinese 3.6% and others 6.8%. The averagenumber of boys and girls per family was 0.09 and 2.70 respectivelyfor couples wanting a boy, and 2.46 and 0.14 for those wantinga girl. The average age of the wives was 34.0 years. These figureswere not significantly different in any ethnic subgroup. Outof all the couples, 80.6% stated that they would have had anotherbaby even had sex preselection not been on offer; 37.5% of thecouples interviewed have been treated so far. The figures amongthose treated are substantially the same as those for the wholegroup. Asian and Middle Eastern couples overwhelmingly wantedboys, whereas European couples showed a slight preference forgirls. These results suggest that, given certain guidelines,sex selection is unlikely to lead to a serious distortion ofthe sex ratio in Britain and other Western societies, but mayneed careful monitoring in other parts of the world.     

Malformation rate and sex ratio in 412 children conceived with epididymal or testicular sperm

BACKGROUND: Follow-up studies of children conceived after ICSI using epididymal or testicular sperm are important due to a still more extensive use of immature male germ cells for ICSI. It is, however, difficult to evaluate the potential risks of malformations of children born after ICSI, overcoming the natural fertilization processes, due to methodological limitations. METHODS: Follow-up study including all children born in Denmark and Norway following ICSI in Denmark, using epididymal or testicular sperm, was done. A questionnaire was sent to the parents between 3 months and 7 years after delivery. RESULTS: Of 341 couples, 329 returned the questionnaire giving a response rate of 96.5%. The study included 412 children, 225 girls and 187 boys, giving a sex ratio (males/males + females) of 45.4% compared with 53.1% in Danish children conceived after conventional IVF without ICSI (P < 0.005). Among a total of 14 (3.4%; 95% confidence interval (CI): 1.9%-5.7%) major malformations, three boys with hypospadias were the most remarkable finding (1.6%; 95% CI: 0.33-4.7%). CONCLUSIONS: An increased frequency of hypospadias in the male offsprings was seen compared with the general population. Apart from this, no increased major malformation rate was detected in ICSI children conceived with epididymal or testicular sperm when compared with malformation rates for IVF or spontaneously conceived children reported in the literature. The sex ratio was significantly lower for ICSI children conceived with epididymal or testicular sperm when compared with children conceived with conventional IVF.     

Sex selection may be inadvertently performed in in-vitro fertilization--embryo transfer programmes

The present study aims to ascertain whether sex selection maybe inadvertently performed in human in-vitro fertilization (IVF)and embryo transfer (IVF-embryo transfer) programmes when selectingfor high quality embryos (those with the fastest cleaving ratesand/or the best morphology) at the fresh transfer cycle. Allpatients entering into the study were treated with gonadotrophinsafter pituitary suppression with gonadotrophin-releasing hormoneagonists (GnRHa) and had intrauterine embryo transfer on day2 post-insemination. These patients were retrospectively dividedinto three groups according to whether the difference in meannumber of cells between embryos transferred and all embryosavailable for transfer in a given cycle was less than (negativeselection), equal to (no selection) or greater (positive selection)than zero. In cycles resulting in singleton births, the sexratio of the resulting babies was significantly (P 0.005) shiftedtoward the female (88.8%) and to the male (90.0%) in the negativeand positive selection groups respectively. No shift in sexratio was observed in cycles resulting in multiple births. Maternalage was another independent factor affecting sex ratio at birth.Sex ratio was significantly (P 0.05) skewed in favour of males(62.7%) and females (71.4%) in women <35 and 235 years ofage respectively. Maternal age, number of embryos transferredand the event of selecting or not selecting the slowest cleavingembryos for transfer were entered automatically in a three-groupdiscriminant model for distinguishing cycles resulting in onlyboys, both boys and girls, and only girls. These data suggestthat (i) sex selection may be inadvertently performed in IVF-embryotransfer programmes when selecting for high quality embryosat the fresh transfer cycles; (ii) human endometria may be favourable,indifferent or hostile to either fast cleaving or slow cleavingembryos depending on maternal age; and (iii) ‘natural’sex selection may be performed for social, psychological ormedical reasons.     

Gender differences at birth and differences in fetal growth

The discrepancy between the number of boys and girls born hasbeen interpreted as a natural selection response to differentialsurvival prospects. There also exists a discrepancy in birthweight, length, head circumference at birth of boys and girls;on the other hand, placental weights were not so strongly biasedby the sex of the fetus. Metabolic differences between the sexesare clearly recognized in adults. It is therefore argued thatthe anthropometric differences at birth, examples of which arepresented in this paper, can only be achieved if the productsof conception are also expressing a sexual bias in metabolismand physiology. It would then be this bias which would determinethe efficiency of the implantation and growth processes andlead to rates of survival to birth. The speculation arisingfrom this and the experimental manipulation of the sex ratiois that the physiological component most likely to be involvedwould be the lipid compartment with its strong sex difference.     

Interactions between breast-feeding, specific parental atopy, and sex on development of asthma and atopy

BACKGROUND: The influence of breast-feeding on the risk of developing atopy and asthma remains controversial. OBJECTIVE: To examine asthma and atopy outcomes by sex, reported specific parental history of atopy, and breast-feeding. METHODS: In a birth cohort, we examined childhood asthma and atopy (positive skin prick tests) by sex and breast-feeding in relation to maternal and paternal atopy. Interactions were explored in logistic regression models. RESULTS: For boys, breast-feeding (odds ratio [OR], 1.63; 95% CI, 0.93-2.87; P = .09) and maternal atopy (OR, 1.95; 95% CI, 0.93-4.08; P = .08) were each associated with atopy at age 13 years. Breast-feeding increased the risk for atopy among boys with paternal atopy (OR, 7.39; 95% CI, 2.21-24.66) compared with non-breast-fed boys with paternal atopy, but did not significantly further increase risk among subjects with maternal atopy. For girls, breast-feeding (OR, 0.74; 95% CI, 0.41-1.31) and maternal and paternal atopy were not independent risk factors for atopy at age 13 years. However, breast-feeding increased the risk for atopy in girls with maternal atopy (OR, 3.13; 95% CI, 1.20-8.14) compared with non-breast-fed girls with maternal atopy. There was no such effect among subjects with paternal atopy. Results for the outcome of asthma followed a similar pattern. CONCLUSION: The influence of breast-feeding on development of atopy and asthma differs by sex and by maternal and paternal atopy, and is most significant among subjects at lower baseline risk. CLINICAL IMPLICATIONS: Analyses of environmental risk factors for asthma and atopy should be stratified by specific parental atopy and sex.     

Genetic and Environmental Factors in Breakfast Eating Patterns

Despite many studies on the prevalence of breakfast eating, we know little about factors that determine breakfast eating patterns. Our aim was to find out to which extent breakfast eating frequency is influenced by genetic and environmental factors using twin and twin-family models in a population sample of 16-year-old twins (n = 5250) and their parents (n = 4663). In common effects sex-limitation models, additive genetic effects explained 41% (95% CI: 21-63%) of the variance in breakfast eating in girls and 66% (95% CI: 47-79%) in boys, and common environmental effects 45% (95% CI: 23-62%) in girls and 14% (95% CI: 5-29%) in boys. Of twin-family models, phenotypic assortment models fitted the data best. Heritability estimates increased somewhat (72%, 95% CI: 46-98% in girls and 63%, 95% CI: 38-89%) in boys. Common family environment remained substantial in both sexes. Cultural transmission was nonsignificant. The relative influence of genetic and family factors on adolescent breakfast eating frequency differs by sex and is generation-specific.     

北京市部分高中生性状况初步调查及其与亲子依恋的关系

目的:调查北京市部分高中生性发育状况及其性行为和性态度与亲子依恋的关系。方法:对北京市两所学校847名高中生用自编青少年性状况信息调查表和修订的青少年-父母依恋问卷(IPPA)进行调查。结果:研究对象报告第一次月经初潮/遗精的平均年龄分别为男生13.2岁,女生12.7岁;性行为发生率为3.3%(男生16人,女生12人),第一次发生性行为的平均年龄为16.0岁;谈恋爱人数占到39.1%;研究对象获取性信息的主要途径为朋友38.8%,科普书籍和报纸24.5%,学校的有关课程(老师)15.8%。在看待同龄人的性态度以及自身性行为方面男生比女生对同龄人性行为持更赞同的态度(14.4±3.9/16.7±3.2,5.8±1.41/5.5±1.1,t=-8.88、3.26,P<0.01)。与父母亲情感依恋不安全的高中生相比,与父亲和母亲都是安全依恋的高中生对同龄人性行为持显著不赞同态度;其自身性行为水平也显著低于前者。结论:北京市部分高中生的性行为和性态度与亲子依恋有关,但关系微弱。     

Prevalence and trends of underweight and BMI distribution changes in Japanese teenagers based on the 2001 National Survey data

BACKGROUND: Excessive thinness has been glamorized among Japanese adolescent girls, and unhealthy dieting to lose weight has become a popular practice among them. The prevalence of underweight in contemporary Japanese girls in comparison with that of boys, however, remains to be studied. AIM: The purpose of this study was to determine the prevalence and trends of underweight in contemporary Japanese teenagers of both sexes using nationally representative cross-sectional data. SUBJECTS AND METHODS: Underweight was defined as BMI < 3rd percentile by age and sex of the 1978-1981 reference population as previously reported. These reference values were compared with BMIs of the contemporary population based on the 2001 Cross-sectional National Survey data of Japanese teenagers (215 972 boys and 216 496 girls). RESULTS: The prevalence of underweight was approximately 2-3% in junior high school students of both sexes, 12.5-14.5 years of age, approximately 3% in senior high school students of both sexes, 15.5-16.5 years of age, and approximately 4% in senior high school students of both sexes, 17.5 years of age. CONCLUSION: The prevalence of underweight decreased among Japanese teenage students of both sexes during the past decades. Female preponderance in the prevalence of underweight was not confirmed.     

Fertility rates in Denmark in relation to the sexes of preceding children in the family

Analysis of the effect of sex combination of previously born children in the family on fertility rates was performed for 363,373 Danish families comprising a total of 613,900 children, to address the questions of sex preference and combination preference. The fertility rates were stratified by parental age, period and latency time to the next child, and fertility rate ratios were estimated using multiplicative Poisson regression models. Our results demonstrate a strong preference for a balanced composition of sexes in Danish families. In families with two or three children the highest fertility rates were seen in families who had same-sexed children. The lowest fertility rates were in families with two children of identical sex followed by a child of the opposite sex. A moderate sex preference for girls was indicated by higher fertility rates in two-boy families than in two-girl families.     

Creatine-kinase and pyruvate-kinase activities in normal children: implications in Duchenne muscular dystrophy carrier detection

Serum creatine-kinase (CK) and pyruvate-kinase (PK) levels were determined in 201 boys and girls less than 15 years old to establish values and to investigate a possible correlation between enzyme activity, sex, and age. It was observed that the mean CK activity in boys was significantly higher than in females (of all ages), whereas it did not differ statistically between girls and women. A slight but significant correlation between CK activity and age was found only in females. The mean PK activity in children was significantly greater than in adult women and it decreased significantly with age in children of both sexes. Furthermore, a slight correlation between CK and PK was observed only in girls. Based on these results, we suggest that the results of CK and PK determinations of females at risk for Duchenne muscular dystrophy should be compared with controls of comparable age and sex.     

The effects of age and sex on mental rotation performance,verbal performance,and brain electrical activity

This study examined the effects of age and sex on mental rotation performance, verbal performance, and brain-wave activity. Thirty-two 8-year-olds (16 boys) and 32 college students (16 men) had EEG recorded at baseline and while performing four computerized tasks: a two-dimensional (2D) gingerbread man mental rotation, a 2D alphanumeric mental rotation, of three-dimensional (3D) basketball player mental rotation, and lexical decision making. Additionally, participants completed a paper- and pencil water level task and an oral verbal fluency task. On the 2D alphanumeric and 3D basketball player mental rotation tasks, men performed better than boys, but the performance of women and girls did not differ. On the water level task, men performed better than women whereas there was no difference between boys and girls. No sex differences were found on the 2D gingerbread man mental rotation, lexical decision-making, and verbal fluency tasks. EEG analyses indicated that men exhibited left posterior temporal activation during the 2D alphanumeric task and that men and boys both exhibited greater left parietal activation than women and girls during the 2D gingerbread man task. On the 3D basketball player mental rotation task, all participants exhibited greater activation of the right parietal area than the left parietal area. These data give insight into the brain activity and cognitive development changes that occur between childhood and adulthood.     

Infants' responses to the still-face situation at five and nine months: focusing on sex differences

This study investigated developmental changes and sex differences in infants' responses to a female stranger during a face-to-face interaction, still-face, and reunion phase. Twenty-two infants (11 boys and 11 girls) were observed at five and nine months of age. At five months, the infants smiled less in the still-face phase, while at nine months the infants smiled less at each subsequent phase. Girls, but not boys, smiled more at nine months than five months. Girls' gazing toward the social partner's face decreased during the still-face and reunion phases. Girls gazed toward the social partner's face more than the boys, independent of the phases and age. The findings support the view the effect of a still-face on infants is robust at both five and nine months and for both sexes. But the effect remained in the reunion phase only for the nine-month-olds. These findings suggest that girls have more interest in their social partner than boys.     

Sex predetermination and the ethics of sex selection

At present there appear to be two main categories of problems involved in the ethics of sex selection. The first has to do with the status of the embryo, and the second has to do with the social consequences of making sex selection widely available. However, these may not be the only issues. There is growing evidence from evolutionary psychology and biology, which suggests that the sex of the offspring in mammals may not, after all, be a matter of chance. Instead, sex allocation in mammals may be the result of a finely tuned adaptive process involving the current suitability of a mother to conceive an offspring of a particular sex. If so, we need to know more about this process before embarking on a social policy that could have disadvantageous outcomes for children, their parents and society as a whole.     

Preferential location of sex chromosomes, their aneuploidy in human sperm, and their role in determining sex chromosome aneuploidy in embryos after ICSI

BACKGROUND: In babies born after ICSI procedures, an increase of de-novo sex chromosome abnormalities has been observed. Several hypotheses have been proposed to explain these findings: an increased rate of sex chromosome aneuploidy in sperm of oligozoospermic men, or a preferential location of the sex chromosomes in the sub-acrosomal region of the sperm nucleus which leads to a reduced DNA decondensation of this region. In order to investigate which theory may be more reliable, we studied the localization of sex chromosomes and their aneuploidy rate in sperm in men undergoing ICSI. METHODS: Using fluorescent in-situ hybridization we studied sex chromosome localization and the aneuploidy rate for sex chromosomes and chromosome 18 in 20 oligospermic men undergoing ICSI and in 10 controls. RESULTS: In 40.94 and 52.92% of cases, the X and Y chromosomes respectively were localized in the sub-acrosomal region of the sperm nucleus compared with only 14.29% of cases of chromosome 18 (P < 0.001). An increase of sex chromosome aneuploidy in sperm of oligospermic men was observed; 2.91 versus 0.69% of controls (P < 0.001). CONCLUSIONS: Sex chromosomes are localized preferentially in the sub-acrosomal region of sperm and sex chromosome aneuploidy rate in the sperm of oligozoospermic men is higher than in controls.     

Prevalence and trends of underweight and BMI distribution changes in Japanese teenagers based on the 2001 National Survey data

Background: Excessive thinness has been glamorized among Japanese adolescent girls, and unhealthy dieting to lose weight has become a popular practice among them. The prevalence of underweight in contemporary Japanese girls in comparison with that of boys, however, remains to be studied.

Aim: The purpose of this study was to determine the prevalence and trends of underweight in contemporary Japanese teenagers of both sexes using nationally representative cross-sectional data.

Subjects and methods: Underweight was defined as BMI?<?3rd percentile by age and sex of the 1978–1981 reference population as previously reported. These reference values were compared with BMIs of the contemporary population based on the 2001 Cross-sectional National Survey data of Japanese teenagers (215 972 boys and 216 496 girls).

Results: The prevalence of underweight was approximately 2–3% in junior high school students of both sexes, 12.5–14.5 years of age, approximately 3% in senior high school students of both sexes, 15.5–16.5 years of age, and approximately 4% in senior high school students of both sexes, 17.5 years of age.

Conclusion: The prevalence of underweight decreased among Japanese teenage students of both sexes during the past decades. Female preponderance in the prevalence of underweight was not confirmed.     

Activity pattern,smoking habits,and somatometric variables of the Czechoslovakian population

Summary A total of 3762 subjects of both sexes, natives of Czechoslovakia, ranging in age from 12–55 years, were examined. Both anamnestic data and selected anthropometric variables were evaluated. The proportion of non-smokers for adult males was 47–56%, and for adult females was 54–74% of the population. The proportion of subjects not engaged in any type of physical activity decreases in boys between 12 and 18 years from 28 to 16%, in girls between 12 and 15 years from 25 to 22%; from then on the trend reverses and the percentage rises up to 42% in men and 65% in women. The number of subjects participating in competitive sporting activity reaches its peak at 18 years, when 46% of boys and 43% of girls compete, but than decreases quickly. 12 year old girls are taller and heavier than boys but at 15 years the relationship is reversed. The LBM at the age of 12 is equal in boys and girls, but from then till 18 years the increase is larger in boys. The LBM weight in adults remains steady, women attaining 77% of the value found in men. The skinfold increases with age similarly in both sexes, except for an interval between 12 and 18 years, when girls show a steeper increase. Adult women attain 121–160% of the values characteristic for men. The grip strength of the right hand equals about 50 kp in adult men and 30 kp in adult women. Within the age range followed, it remains unaffected by age.More than 50 specialists assisted in gathering the pertinent data     

Sex differences in FSH-regulatory peptides in pubertal age boys and girls and effects of sex steroid treatment

BACKGROUND: FSH concentrations are higher in girls than in boys before puberty. We hypothesized that steroid-mediated changes in FSH-regulatory proteins underlie the sex differences in FSH secretion and pubertal timing. METHODS: FSH-regulatory proteins, LH, FSH and sex steroids were measured in five boys, 10 girls, and five girls with Turner syndrome before and during sex steroid treatment (girls, 0.05 mg/day estradiol; boys, 5 mg/day testosterone) for up to 4 weeks. Blood was obtained every 15 min from 20.00 to 08.00 h before and during sex steroid treatment. RESULTS: The mean FSH concentration was higher in girls than in boys (P = 0.0044). Activin-A concentrations were greater (P < 0.0001) and inhibin-B concentrations lower (P < 0.0001) in girls compared with boys. Steroid treatment (i) suppressed LH/FSH concentrations in all subjects; (ii) increased the mean activin-A concentration in all but the Turner girls (P = 0.001); and (iii) decreased inhibin-B concentrations in boys (P = 0.005) but not in girls. Total follistatin and follistatin 288 concentrations did not differ by sex. CONCLUSIONS: Sex steroids regulate circulating activin-A and inhibin-B concentrations in children. The lower inhibin-B and higher activin-A concentrations may explain the higher FSH and earlier onset of puberty in girls.     

Risk factors for wheezing in early adolescence: a prospective birth cohort study in Brazil.

BACKGROUND: Many asthma studies are available in the literature, but few investigated whether risk factors for asthma differ by sex. OBJECTIVE: To evaluate risk factors for wheezing in early adolescence, with emphasis on sex differences. METHODS: A prospective birth cohort study was initiated in 1993; 87.5% of the original cohort was traced at 11 years, totaling 4,452 adolescents. Current wheezing was defined as at least 1 crisis in the previous 12 months. The following independent variables were analyzed: maternal smoking during pregnancy, wheezing at 4 years, maternal wheezing, and adolescent body mass index. RESULTS: Current wheezing affected 13.5% (95% confidence interval [CI], 12.4%-14.5%) of the cohort. The prevalence of current wheezing was 15.3% (95% CI, 13.7%-16.8%) in boys and 11.7% (95% CI, 10.4%-13.1%) in girls (P < .001). Maternal smoking was related to an increased risk of wheezing for boys but not for girls. There was a significant tracking of wheezing from 4 to 11 years in both sexes, although the magnitude was stronger for boys. A dose-response association between maternal wheezing and adolescent wheezing was observed in boys but not in girls. Finally, obesity was associated with an increased risk of wheezing in boys but not in girls. CONCLUSIONS: The variables explored in this investigation had a stronger effect on adolescent wheezing in boys than in girls. Public health strategies aimed at minimizing the burden of wheezing should take these sex differences into account.     

Sex differences in pubertal growth of the heart

The aim of this study was to determine sex differences in growth of the heart during puberty. Three-year increments of growth of the heart and body structures and functions related to heart size were compared between the sexes. Echocardiographically estimated left ventricular mass (LVM) represented heart size, body surface area (BSA) represented the area supplied by the left ventricle, and diastolic blood pressure (DBP) represented a segment of arterial resistance. Pubertal changes in these and several other parameters were compared in 67 healthy girls and 84 healthy boys followed longitudinally from 11.5 to 14.5 years. Increments were compared by t-tests. Left ventricular mass of boys was larger than in girls. The sex difference was not significant at 11.5 years, but increased during the three pubertal years. LVM increased 26% in girls and 53% in boys (P <.001). During the same period, BSA increased 22% in girls and 29% in boys (P <.001), while DBP increased 6% in girls and 9% in boys (P <.05). The larger increment of BSA and DBP in boys corresponds to the sex difference in the increment of the heart size. These differences account, in part, for the greater increase (P <.001) in physical working capacity in boys compared to girls. Am. J. Hum. Biol. 9:297–302, 1997. © 1997 Wiley-Liss, Inc.