A colleague of mine works in reproductive toxicology and he dumped out the following references. Neither he nor I can vouch for the quality of any of these studies, but they do cover many of the points discussed on edstat-l. Reference List 1. Allan, B. B.; Brant, R.; Seidel, J. E., and Jarrell, J. F. (BB Allan/Foothills Prov Gen Hosp/Dept Obstet & Gynecol/1403-29TH St NW/Calgary/Ab T2N 2T9, Canada). Declining sex ratios in Canada. Canadian Medical Association Journal. 1997 Jan 1; 156(1):37-41; ISSN: 0820-3946. Rec #: 18034 Notes: English Article Abstract: Objective: To examine the trends in the proportion of annual live births that were male in Canada and to compare the trends with those in the United States. Design: Analysis of census data. Setting: Canada as a whole and 4 main regions (West, Ontario, Quebec and Atlantic). Subjects: All live births from 1930 to 1990. Outcome measures: Sex ratio (expressed as the proportion of total live births that were male [male proportion]) overall and by region. Results: The male proportion in Canada decreased significantly after 1970 (p < 0.001); this represented a cumulative loss of 2.2 male births per 1000 live births from 1970 to 1990. Although a decrease was observed in all four regions studied, only that in the Atlantic region was significant (p < 0.001), representing a cumulative loss of 5.6 male births per 1000 live births from 1970 to 1990. A significant decrease in the male proportion was also observed in the United States from 1970 to 1990 (p < 0.001), although to a lesser degree than that observed in Canada, and represented a cumulative loss of 1.0 male births per 1000 live births. Conclusions: The decreased sex ratio in Canada adds to the growing debate over changes in biological markers and their potential causes. In addition,the study illustrates the potential use of the sex ratio as a widely available, unambiguous measure of the reproductive health of large populations. 2. Andersson, R. and Bergstrom, S. (R Andersson/Ctr Med/Gamboula, Cent Afr Republ). Is maternal malnutrition associated with a low sex ratio at birth? Human Biology. 1998 Dec; 70(6):1101-1106; ISSN: 0018-7143. Rec #: 21650 Notes: English Article Abstract: The low male/female ratio at birth in African populations has been attributed to a variety of genetic, behavioral, and environmental factors. A low sex ratio at birth has been associated with maternal malnutrition in mammals, but this issue has not been studied in humans. In this study we analyzed the relation between maternal nutritional status and sex ratio at birth in 3282 children born to 684 women from a rural African society. Short maternal stature and obesity were independently related to a low sex ratio at birth. These results are consistent with animal experiments that indicate an adverse effect of maternal malnutrition on male fetuses. The results warrant further research in this area. 3. Astolfi, P. and Zonta, L. A. (P Astolfi/Univ Pavia/Dept Genet & Microbiol A Buzzati Traverso/Via Abbiategrasso 207/I-27100 Pavia/ITALY). Sex ratio and parental age gap. Human Biology. 1999 Feb; 71(1):135-141; ISSN: 0018-7143. Rec #: 22121 Notes: English Article Abstract: We tested the hypothesis that a large age difference between parents can shift the sex ratio at birth in favor of males, as Manning et al. (1997) suggested in their analysis of English and Welsh data. Among children born in Lombardy (northern Italy) in 1990 and 1991, we observed an anomalous excess of males born to a particular subsample of parents with a wide age Sap (>15 yr) between them; in the overall sample the father-mother age gap does not significantly contribute to the determination of the child's sex. 4. Bean, B. Progenitive Sex Ratio Among Functioning Sperm Cells. American Journal of Human Genetics 1990;47(2):351-353. Rec #: 5089 5. Check, J. H.; Kwirenk, D.; Katsoff, D.; Press, M.; Breen, E., and Baker, A. (JH Check/7447 Old York Rd/Melrose Pk, PA 19126 USA). Male:female sex ratio in births resulting from IVF according to swim-up versus Percoll preparation of inseminated sperm. Archives of Andrology. 1994 Jul-1994 Aug 31; 33(1):63-65; ISSN: 0148-5016. Rec #: 11305 Notes: English Article Abstract: Two centers have independently reported a higher rate of male to female births following insemination of sperm prepared by a modified swim-up technique. The principle of the modified swim-up is that a small percentage of the x-bearing sperm are the fastest and travel to the top of the supernatant, followed by the y-bearing sperm; the bulk of the x-bearing sperm remain in the pellet. In this technique, the very top layer is discarded and the resulting supematant is collected, leaving only the pellet. In contrast, with the conventional swim-up technique, the entire supematant is collected. The study presented herein retrospectively evaluated the male to female sex ratio of births from in vitro fertilization using standard swim-up technique and compared these results to the ratio obtained from separating with Percoll. There were 53% male births with swim-up vs. 54% with Percoll in singleton pregnancies and 51% males with swim-up vs. 40% with Percoll with multiple births. Thus, conventional swim-up alone does not increase percentage of male births. 6. Chu, C. Y. C. and Yu, R. (CYC Chu/Natl Taiwan Univ/Dept Econ/Taipei, Taiwan). Individual sex preferences and the population sex ratio of newborns. Journal of Theoretical Biology. 1998 Oct 7; 194(3):383-390; ISSN: 0022-5193. Rec #: 21552 Notes: English Article Abstract: This paper proposes the hypothesis that countries with stronger sex preferences are more likely to have a negative relationship between crude birth rates and male/female ratios of newborn babies. Conversely, the existence of a significantly negative relationship in any country may also be a supportive evidence of its preferences for sons. Our hypothesis is both behavioral and biological: on the behavioral side, parents with strong sex preferences are inclined to continue to bear children if the existing sex ratio of children is less than desirable. On the biological side, parents with many girls are more likely to be ''girl producers'', who with individual-specific biological characteristics tend to generate higher female births. We use the macro data in the United Nations Demographic Yearbook to verify and test our hypothesis. For developing countries which do not have reliable micro data on fertility, our approach using macro data is a useful and interesting alternative. (C) 1998 Academic Press. 7. Clarke, C. A. and Mittwoch, U. (CA Clarke/Univ Liverpool/43 Caldy Rd/Wirral L48 2HF/Merseyside, England). Changes in the male to female ratio at different stages of life. British Journal of Obstetrics and Gynaecology. 1995 Sep; 102(9):677-679; ISSN: 0306-5456. Rec #: 15572 Notes: English Editorial 8. D.H. Moore II, B. L. Gledhill. How large should my study be so that I can detect an altered sex ratio? Fertility and Sterility 50:21-25 1988. Rec #: 2934 9. Davis, D. L.; Gottlieb, M. B., and Stampnitzky, J. R. (DL Davis/World Resources Inst/1709 New York Ave NW/Washington, DC 20006 USA). Reduced ratio of male to female births in several industrial countries: A sentinel health indicator? JAMA - Journal of the American Medical Association. 1998 Apr 1; 279(13):1018-1023; ISSN: 0098-7484. Rec #: 20287 Notes: English Article Abstract: Context.-The sex ratio of 1.06:1, the ratio of male to female births, has declined over the past decades. Recent reports from a number of industrialized countries indicate that the proportion of males born has significantly decreased, while some male reproductive tract disorders have increased. Objectives.-To examine the evidence for declines in the male proportion at birth and suspected causes for this decline, and to determine whether altered sex ratio can be considered a sentinel health event. Data Sources.-Birth records were analyzed from national statistical agencies. Study Selection.-Published analyses of trends in ratio of males to females at birth and studies of sex determinants evaluating epidemiological and endocrinological factors. Data Extraction.-Proportion of males born, 1950-1994 in Denmark; 1950-1994 in the Netherlands; 1970-1990 in Canada; and 1970-1990 in the United States, Data Synthesis.-Since 1950, significant declines in the proportion of males born have been reported in Denmark and the Netherlands. Similar declines have been reported for Canada and the United States since 1970 and parallel declines also have occurred in Sweden, Germany, Norway, and Finland. In Denmark, the proportion of males declined from 0.515 in 1950 to 0.513 in 1994. In the Netherlands, the proportion of males declined from 0.516 in 1950 to 0.513 in 1994, Similar declines in the proportion of males born in Canada and the United States are equivalent to a shift from male to female births of 8600 and 38 000 births, respectively. Known and hypothesized risk factors for reduced sex ratio at birth cannot fully account for recent trends. Conclusion.-Patterns of reduced sex ratio need to be carefully assessed to determine whether they are occurring more generally, whether temporal or spatial variations are evident, and whether they constitute a sentinel health event. 10. Dickinson, H. and Parker, L. (H Dickinson/Univ Newcastle upon Tyne/Sch Med/Dept Child Hlth/Childrens Canc Unit/Newcastle Tyne NE2 4HH, England). Do alcohol and lead change the sex ratio? Journal of Theoretical Biology. 1994 Aug 7; 169(3):313-315; ISSN: 0022-5193. Rec #: 11420 Notes: English Article Abstract: It has been suggested that exposure to alcohol and lead may decrease testosterone levels in men which in turn may lead to an increase in the proportion of girls among their offspring. This hypothesis is tested on a new dataset of 268 109 children born in Cumbria from 1950-89. From fathers' occupations given on birth certificates, we calculated the sex ratio for offspring of men exposed occupationally to alcohol and lead. We carried out a meta-analysis of the present and previous studies. The results are consistent with the hypothesis that alcohol and lead lower the sex ratio. 11. Dickinson, H. O. and Parker, L. (HO Dickinson/Univ Newcastle upon Tyne/Royal Victoria Infirm/N England Childrens Canc Res Unit/Newcastle upon Tyne NE1 4/Tyne & Wear, England). Sex ratio in relation to fathers' occupations. Occupational and Environmental Medicine. 1997 Dec; 54(12):868-872; ISSN: 1351-0711. Rec #: 19969 Notes: English Article Abstract: Objective-To investigate whether the sex ratio of children varies between fathers of different occupations. Methods-The sex ratio (the ratio of the number of boys to the number of girls at birth) was calculated in relation to paternal occupation in the cohort of all 253 433 live births in Cumbria, north west England, from 1950-89. Exact binomial confidence intervals were used to estimate whether the sex ratio in each occupational category was significantly different from that for the rest of the cohort. Results-There were fewer occupational categories with significantly different sex ratios at the 5% level than expected by chance alone, assuming the same binomial distribution of sexes at birth within each paternal occupation. Conclusions-Significant variation of the sex ratio with fathers' occupations was not found. There is some evidence that the sex ratio shows less variance than expected under a binomial model which assumes independence of the sex of each child; a possible explanation of this may be parental preference for limiting family size after children of both sexes have been born or some other factor which results in children within a family being more likely to be of both sexes rather than the same sex. 12. DICKINSON, H. O. PARKER BINKS WAKEFORD SMITH. THE SEX RATIO OF CHILDREN IN RELATION TO PATERNAL PRECONCEPTIONAL RADIATION DOSE: A STUDY IN CUMBRIA, NORTHERN ENGLAND. JOURNAL OF EOIDEMIOLOGY AND COMMUNITY HEALTH . 1996; 50(6):645-652. Rec #: 21229 13. Fukuda, M.; Fukuda, K.; Shimizu, T., and Moller, H. (M Fukuda/Fukuda Ladies Clin/30-9 Kariya/Ako/Hyogo 6780239, Japan). Decline in sex ratio at birth after Kobe earthquake. Human Reproduction. 1998 Aug; 13(8):2321-2322; ISSN: 0268-1161. Rec #: 21321 Notes: English Article Abstract: We investigated the possible association between the Kobe earthquake (January 1995) and the sex ratio among liveborn infants after the catastrophe. A significant decline in the sex ratio (0.501) of Hyogo Prefecture in October 1995 was observed 9 months after the Kobe earthquake as compared with an expected value of 0.516 in the period from January 1993 to January 1996 (P = 0.04; one-tailed). Simultaneously, a reduction in fertility of similar to 6% was also observed, compared with the month of October 2 years previously Thus, the acute stress resulting from a great natural catastrophe can be a cause of a low sex ratio at birth 9 months later. 14. Gray, R. H.; Simpson, J. L.; Bitto, A. C.; Queenan, J. T.; Li, C. J.; Kambic, R. T.; Perez, A.; Mena, P.; Barbato, M.; Stevenson, W., and Jennings, V. (RH Gray/Johns Hopkins Univ/Sch Hyg & Publ Hlth/Dept Populat Dynam/600 N Wolfe St/Baltimore, MD 21205 USA). Sex ratio associated with timing of insemination and length of the follicular phase in planned and unplanned pregnancies during use of natural family planning. Human Reproduction. 1998 May; 13(5):1397-1400; ISSN: 0268-1161. Rec #: 20781 Notes: English Article Abstract: This was a multicentred, prospective study of pregnancies among women using natural family planning. The women maintained natural family planning charts of the conception cycle, recording acts of intercourse and signs of ovulation (cervical mucus changes, including peak day and basal body temperature). Charts were used to assess the most probable day of insemination relative to the day of ovulation and length of the follicular phase of the cycle. The sex ratio (males per 100 females) for 947 singleton births was 101.5, not significantly different from the expected value of 105. The sex ratio did not vary consistently or significantly with the estimated timing of insemination relative to the day of ovulation, with the estimated length of the follicular phase or with the planned or unplanned status of the pregnancy, Although these findings may be affected by imprecision of the data, the study suggests that manipulation of the timing of insemination during the cycle cannot be used to affect the sex of offspring. 15. J H ALFREDSSON. ARTIFICAL INSEMINATION WITH FROZEN SEMEN. SEX RATIO AT BIRTH. INTERNATIONAL JOURNAL OF FERTILITY 29:152-155 1984. Rec #: 857 16. James, W. H. (WH James/Univ London Univ Coll/Galton Lab/Wolfson House/4 Stephenson Way/London NW1 2HE, England). Hypotheses on mammalian sex ratio variation at birth. Journal of Theoretical Biology. 1998 May 7; 192(1):113-116; ISSN: 0022-5193. Rec #: 20720 Notes: English Article Abstract: Some comments are made on two hypotheses on the variation of mammalian sex ratios (proportions male) at birth viz. Krackow's developmental asynchrony hypothesis and my parental hormone hypothesis. It seems not unfair to characterise his hypothesis as functioning to support the conventional Mendelian paradigm. In contrast, if my hypothesis were true, some adjustment would have to be made to that paradigm. Here I suggest further ways of testing Krackow's hypothesis experimentally. In contrast, my own hypothesis seems to lend itself also to testing by epidemiological methods; here it is suggested that the offspring sex ratios of several specified categories of ill men should be low. (C) 1998 Academic Press Limited. 17. James, William H. The hypothesized hormonal control of mammalian sex ratio at birth-a second update. J. Theor. Biol. 1992; 155121-128. Rec #: 8086 18. Juntunen, K. and Kauppila, A. (K Juntunen/Family Federat Finland/Oulu Kiviharjuntie 11/Oulu 90220, Finland). Variation of sex ratio within very large sibships. Human Reproduction. 1998 May; 13(5):1412-1413; ISSN: 0268-1161. Rec #: 20786 Notes: English Letter 19. Juntunen, K. S. T.; Kvist, A. P., and Kauppila, A. J. I. (KST Juntunen/Family Federat Finland/Kiviharjuntie 11/Oulu 90220, Finland). A shift from a male to a female majority in newborns with the increasing age of grand grand multiparous women. Human Reproduction. 1997 Oct; 12(10):2321-2323; ISSN: 0268-1161. Rec #: 19985 Notes: English Article Abstract: In this longitudinal study, we investigated the relationship of birth order and the age of mother and father to the gender of 1795 newborns (mean +/- SD 12.5 a 1.6 per mother) of 143 grand grand multiparas (i.e women who have had >10 deliveries). The frequency of boys was 52.2% in the group of Ist to 9th paras and 46.2% in the group of 10th to 20th paras (P = 0.022). Mothers aged greater than or equal to 35 years had 7.0% more female than male newborns (P = 0.024). The respective figure for fathers was 5.6% (P = 0.023). The interpregnancy interval evaluated for 96 mothers with 1091 deliveries had no correlation with the gender of the infants. In the stepwise logistic regression analysis, the age of the mothers remained the only significant independent factor for the shift from a male to a female majority in the newborns (P = 0.0389). The present data thus indicate that the age of the mother is the factor which explains why grand grand multiparous women deliver more girls than boys. 20. Lerchl, A. (A Lerchl/Univ Munster/Inst Reprod Med/Domagkstr 11/D-48129 Munster, Germany). Seasonality of sex ratio in Germany. Human Reproduction. 1998 May; 13(5):1401-1402; ISSN: 0268-1161. Rec #: 20782 Notes: English Article Abstract: It was investigated whether there is a seasonal variation in sex ratio at birth in Germany. The analysis was based on records from the German Bureau for Statistics, covering the period from 1946 to 1995. A highly significant (P less than or equal to 0.001), albeit low-amplitude rhythm was found with two peaks in May and December, and two nadirs in March and October. No correlations were found between sex ratios and seasonal birth rates during this period. 21. Marcus, M.; Kiely, J.; Xu, F. J.; Mcgeehin, M.; Jackson, R., and Sinks, T. (M Marcus/Ctr Dis Control & Prevent/Natl Ctr Environm Hlth/4770 Buford Highway/Chamblee, GA 30341 USA). Changing sex ratio in the United States, 1969 -1995. Fertility and Sterility. 1998 Aug; 70(2):270-273; ISSN: 0015-0282. Rec #: 21115 Notes: English Article Abstract: Objective: To determine if the sex ratio of live births in the United States has changed during the 27 years from 1969 through 1995. Design: Regression analysis of secular trends in sex ratios. Setting: Population-based data. Patient(s): Liveborn infants in the United States 1969-1995. Main Outcome Measure(s): Sex of liveborn infant. Result(s): The sex ratio (number of male births divided by number of female births) declined significantly among whites during the 27 years under study. Among black newborns, the sex ratio significantly increased during the same time period. Conclusion(s): These secular trends could not be explained by changing maternal or paternal age, or by changing proportions of specific birth orders. Possible explanations for the observed changes in sex ratio include random fluctuations in sex ratio over time, changes in demographic characteristics of the population (other than the characteristics controlled for in this analysis), and changes in frequency or timing of intercourse. Environmental exposures are unlikely to account for the observed trends. (Fertil Steril(R) 1998;70:270-3. (C)1998 by American Society for Reproductive Medicine.). 22. Martin, R. and Rademaker, A. W. A Study of Paternal Age and Sex Ratio in Sperm Chromosome Complements. Human Heredity. 1992 Nov-1992 Dec 31; 42(6):333-336. Rec #: 8690 23. Martin, R. H. Sex Ratio Among Sperm Cells. American Journal of Human Genetics 1990;47(2):349-351. Rec #: 5088 24. Martin, R. H.; Spriggs, E.; Ko, E., and Rademaker, A. W. (RH Martin/Alberta Childrens Prov Gen Hosp/Dept Med Genet/1820 Richmond Rd SW/Calgary/Ab T2T 5C7, Canada). The relationship between paternal age, sex ratios, and aneuploidy frequencies in human sperm, as assessed by multicolor FISH. American Journal of Human Genetics. 1995 Dec; 57(6):1395-1399; ISSN: 0002-9297. Rec #: 15884 Notes: English Article Abstract: We studied the frequencies of X- and Y-chromosome-bearing sperm, diploidy and disomy for chromosomes 1, 12, X, and Y in sperm from 10 normal men aged 21-52 years, to determine whether there was any relationship between donor age and any of these variables. Multicolor FISH was used to control for lack of probe hybridization and to distinguish diploid sperm from disomic sperm. A minimum of 10,000 sperm per donor was evaluated for each chromosome, for a total of 225,846 sperm studied. Sperm were considered disomic if two fluorescent signals were separated by a minimal distance of one signal domain. The mean frequencies of X- and Y-bearing sperm were 50.1% and 49.0%, respectively; not significantly different from 50%. There was no correlation between paternal age and ''sex ratio'' in sperm. Similarly, there was no association between the frequency of diploid sperm (mean, .16%; range, .06%-.42%) and donor age. For disomy frequencies, there was no relationship between donor age and disomy 12 (mean, .16%; range, .10%-.25%), XX (mean, .07%; range, .03%-.17%), and XY sperm (mean, .16%; range, .08%-.24%). There was a significant increase in the frequency of YY sperm (P = .04; mean, .18%; range, .10%-.43%) and disomy 1 sperm (P = .01; mean, .11%; range, .05%-.18%) with donor age. In summary, our results do not support a correlation between paternal age and sex ratio or diploidy. A relationship between paternal age and disomy was observed for disomy 1 and YY sperm but not for disomy 12, XX or XY sperm. 25. Moller, H. (H Moller/Danish Natl Res Fdn/Ctr Res Hlth & Social Stat/Sejrogade 11/DK-2100 Copenhagen O, Denmark). Trends in sex-ratio, testicular cancer and male reproductive hazards: Are they connected? APMIS. 1998 Jan; 106(1):232-238; ISSN: 0903-4641. Rec #: 20208 Notes: English Article Abstract: In the last few decades, the male proportion of newborn babies has been decreasing in several populations. The changes are very small and without practical importance per sc, but the underlying biological mechanisms are not known. In the same period, testicular cancer incidence has increased, and there has been indications of decreasing sperm counts in men in several populations. The available knowledge on factors that influence the sex-ratio in humans supports the idea that an excess of girls in the offspring of a man may be an indicator of reproductive hazards. Data from a Danish case-control study show strong associations between testicular cancer, low fertility and a low M:F sex-ratio in the offspring. It is proposed as a hypothesis that there may exist common aetiological factors for testicular cancer, low fertility and low offspring sex-ratio, and that a search for the causal factors involved may focus on agents that can act prenatally to disrupt the normal development and differentiation of the male reproductive organs. 26. Moller, H.; Jacobsen, R.; Tjonneland, A., and Overvad, K. (H Moller/Danish Natl Res Fdn/Ctr Res Hlth & Social Stat/DK-2100 Copenhagen O, Denmark). Sex ratio of offspring of diabetics. Lancet. 1998 May 16; 351(9114):1514-1515; ISSN: 0140-6736. Rec #: 20642 Notes: English Letter 27. Moynihan, J. B. and Breathnach, C. S. (JB Moynihan/Univ Coll Dublin/Dept Human Anat & Physiol/Earlsfort Terrace/Dublin 2/IRELAND). Changes in male : female ratio among newborn infants in Ireland. Apmis. 1999 Apr; 107(4):365-368; ISSN: 0903-4641. Rec #: 22437 Notes: English Article Abstract: Trends in the male proportion of live births in Ireland were examined by extracting the numbers of male and female live births from Registrar General's Reports (1864-1952) and Department of Health Annual Reviews (1953-1996), and subjecting them to statistical analysis. Except for 10 years (1947-1956) the proportion of male births has risen, significantly so since 1957. The global fall in male proportion of live births in recent decades has not been seen in Ireland, even though the country has undergone progressive industrialisation. It would be prudent not to assume that the same environmental factors alter sex ratio and cause pathological changes in male reproductive organs. 28. Owens, I. P. F. and Thompson, D. B. A. (IPF Owens/Zool Soc London/Inst Zool/Regents Pk/London NW1 4RY, England). Sex differences, sex ratios and sex roles. Proceedings of the Royal Society of London Series B - Biological Sciences. 1994 Nov 22; 258(1352):93-99; ISSN: 0962-8452. Rec #: 11873 Notes: English Article Abstract: Sexual selection theory predicts that sex roles will be determined by the operational sex ratio (OSR), the sex ratio among individuals searching for mates at any given time. There are two predictions: (i) the sex which is in 'excess' will be the more competitive sex with respect to access to mates; and (ii) the sex of which there is a 'shortage' will be the more choosy with respect to potential partners. We examine the second prediction and find that current OSR theory does not consider an important factor which affects mate choice. This factor is sex differences in variation in mate quality. Hence, we develop a new model of mate choice which shows that the parameter which should be optimized during mate choice is the trade-off between reproductive rate and mate quality. If mate choice is too lax, reproductive rate may be high but partners will be of low quality. If mate choice is too stringent, partners will be of high quality but reproductive rate will be low because such partners will be rare. Stringency of mate choice is, therefore, a facet of OSR theory. Indeed, our model shows that OSR theory can be used to integrate the effect of sex differences in both mating rate and variation in mate quality to predict the direction of mate choice. Our model suggests that: (i) mate choice is only selected when individuals of the opposite sex vary in their quality as mates; (ii) if the extent of variation in mate quality is equal within each sex, the sex with the lower potential mating rate will be the more choosy sex; but (iii) if there is sufficiently greater variation in mate quality among the sex with the lower potential reproductive rate, the sex with the higher potential mating rate will be the more choosy sex. Additionally, this approach demonstrates that competition and choice need not necessarily be opposite sex roles, as is commonly assumed. This is because subtly different forms of the OSR are used to predict competitive and choosy behaviour, respectively. 29. Parazzini, F.; Lavecchia, C.; Levi, F., and Franceschi, S. (F Parazzini/Mario Negri Inst Pharmacol Res/Via Eritrea 62/I-20157 Milan, Italy). Trends in male:female ratio among newborn infants in 29 countries from five continents. Human Reproduction. 1998 May; 13(5):1394-1396; ISSN: 0268-1161. Rec #: 20780 Notes: English Article Abstract: We have analysed trends in male:female ratios among newborns between 1950 and 1990 in 29 countries from five continents. The numbers of liveborn males and females over the period 1950-1994 were derived from the World Health Organization (WHO) database. Countries for which reliable data were available included 20 major European countries (excluding the former Soviet Union, Albania and a few small countries), Canada, the USA, selected countries of Central and South America, Japan, Australia and New Zealand, >From the original numbers of males and females, we computed the proportion of males among liveborns for each country and for selected broader areas within Europe. In most countries the proportion of male liveborns was constant during the study period, In particular, the proportion of male newborns in the European Union was 0.515 in 1950-1954, 0.514 in 1970-1974 and 0.514 in 1990-1994, In the USA, corresponding values were 0.513, 0.513 and 0.512, In Japan the ratios were 0.513 in 1950-1954, 0.516 and 1970-1974 and 0.514 in 1990-1994, Decreasing ratios were observed in some northern and eastern European countries plus Greece and Portugal and, particularly, in Mexico. In contrast, the proportion of male liveborns tended to increase in southern Europe and Australia. Overall, among the 29 countries considered, the proportion of males declined in 16, increased in six, and remained stable in seven. 30. Paterson, A. D. (AD Paterson/Clarke Inst Psychiat/Neurogenet Sect/250 Coll St/Toronto/on M5T 1R8, Canada). Sex ratio of offspring of diabetics. Lancet. 1998 May 16; 351(9114):1515; ISSN: 0140-6736. Rec #: 20641 Notes: English Letter 31. Pera, M.; Moller, H.; Skakkebaek, N. E.; Daugaard, G.; Byskov, A. G.; Rorth, M.; Bishop, T.; Short, R.; Grigor, K., and Clegg, E. Trends in sex-ratio, testicular cancer and male reproductive hazards: Are they connected? Discussion. APMIS. 1998 Jan; 106(1):238-239; ISSN: 0903-4641. Rec #: 20209 Notes: English Editorial 32. Rogan, W. J.; Gladen, B. C.; Guo, Y. L. L., and Hsu, C. C. (WJ Rogan/NIEHS/POB 12233/Res Triangle Pk/NC 27709 USA). Sex ratio after exposure to dioxin-like chemicals in Taiwan. Lancet. 1999 Jan 16; 353(9148):206-207; ISSN: 0140-6736. Rec #: 22053 Notes: English Article 33. Sapp, M. C. and Martindeleon, P. A. (PA Martindeleon/Univ Delaware/Sch Life & Hlth Sci/Newark, DE 19711). Sperm Age, Sex Ratio, and Hyperhaploidy Frequency in Mice. Cytogenetics and Cell Genetics. 1992; 61(1):61-66; ISSN: 0301-0171. Rec #: 8415 Notes: English Article Abstract: Physiologically aged and unaged sperm from each of 12 sexually mature B6SJLF1/J mice were used to fertilize oocytes from females of the same strain, with each male serving as its own control. Male genomes in 323 and 307 first-cleavage metaphases obtained by in vivo and in vitro fertilization, respectively, were analyzed cytogenetically, using C-banding for detection of the Y chromosome. The sex (X:Y) ratio among all zygotes resulting from in vivo fertilization was 1.18; in zygotes resulting from in vivo fertilization by aged (I 4-d mating intervals) sperm, however, the ratio was 1.53, which differed significantly (chi-2 = 6,72, P < 0.01) from the theoretical value of 1.00. Comparison of the sex ratio in zygotes resulting from in vivo fertilization by unaged sperm (3-d mating intervals), 0.94, with that in zygotes resulting from fertilization by aged sperm (using a 2 x 2 contingency table) showed a significant (chi(c)2 = 4.19, P < 0.05) relationship between sex ratio and sperm age. In vitro, neither the combined nor the individual 3- and 14-d data deviated significantly from the expected sex ratio of 1.00. The frequency of sperm-derived hyperhaploidy did not differ significantly between the in vivo (3.4%) and in vitro (5.9%) populations, but did between unaged (2.5%) and aged (6.8%) sperm (chi(c)2 = 5.74, P < 0.01). All hyperhaploid zygotes had a complement of n + 1 chromosomes, except the 14-d in vitro group, where complements of n + 2 and n + 3 chromosomes were seen. Sperm-derived polyploidy, which was observed only in the in vitro group. was independent of sperm age and occurred in 6.8% of the zygotes. These data provide support for the sperm-aging hypothesis and indicate, for the first time, an influence of sperm aging in the male genital tract on the X:Y ratio of conceptuses resulting from natural matings of chromosomally normal males. 34. Savitz, D. A. (DA Savitz/Univ N Carolina/Sch Publ Hlth/Dept Epidemiol/Chapel Hill, NC 27515 USA). Offspring sex ratio as a potential monitor of reproductive disorders in communities near hazardous chemical sites - Reply. Reproductive Toxicology. 1997 Nov-1997 Dec 31; 11(6):894-895; ISSN: 0890-6238. Rec #: 19895 Notes: English Letter 35. Vandenbroek, J. M. (JM Vandenbroek/Netherlands Biol Assoc/Bionieuws/POB 8447/NL-3503 Rk Utrecht, Netherlands). Change in male proportion among newborn infants. Lancet. 1997 Mar 15; 349(9054):805; ISSN: 0140-6736. Rec #: 18361 Notes: English Letter 36. Vankooij, R. J. and Vanoost, B. A. (RJ Vankooij/Univ Hosp Utrecht/Dept Reprod Med/Div Obstet & Gynecol/Heidelberglaan 100/3584 Cx Utrecht, Netherlands). Determination of Sex Ratio of Spermatozoa with a Deoxyribonucleic Acid-Probe and Quinacrine Staining - A Comparison. Fertility and Sterility. 1992 Aug; 58(2):384-386. Rec #: 8162 Notes: English Article Abstract: Objective: To evaluate sex selection of spermatozoa. Design: A deoxyribonucleic acid (DNA) probe (pDP34) detecting distinguishable loci on both X and Y chromosome was used to validate the quinacrine-staining method that is often used for determination of the percentage of Y-bearing sperm. Sperm samples were centrifuged over Percoll to obtain samples with a high X:Y ratio according to the quinacrine-staining method. Controls (sperms before processing over Percoll) and processed sperms were subjected to DNA extraction and analysis with the DNA probe. Results: The DNA analysis revealed a 1.0 X:Y ratio of the spermatozoa before and after Percoll separation. Conclusion: We conclude that the quinacrine method is not suitable for evaluation of methods that claim to separate X and Y-bearing sperm. 37. Weijin, Z. and Olsen, J. (Z Weijin/Aarhus Univ/Steno Inst Publ Hlth/Danish Epidemiol Sci Ctr/DK-8000 Aarhus C, Denmark). Offspring sex ratio as an indicator of reproductive hazards. Occupational and Environmental Medicine. 1996 Jul; 53(7):503-504; ISSN: 1351-0711. Rec #: 16959 Notes: English Letter Steve Simon, [EMAIL PROTECTED], Standard Disclaimer. STATS - Steve's Attempt to Teach Statistics: http://www.cmh.edu/stats =========================================================================== This list is open to everyone. 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