Cycle day of insemination, sex ratio of offspring and duration of gestation

Wh, James

doi:10.1080/03014469400003262

Cited by 33 publications

(14 citation statements)

References 9 publications

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“…It is not clear whether the explanation of these data may lie in the first component or the second. It is known that short gestations are associated with male births (James, 1994). It seems that Jongbloet et a/.…”

Section: Interpregnancy Intervals High Maternal Age and Seasonal Effmentioning

confidence: 99%

Further concepts on regulators of the sex ratio in human offspring: Interpregnancy intervals, high maternal age and seasonal effects on the human sex ratio

James¹

1996

Human Reproduction

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Seasonally of general births and secondary sex ratio in the 17th and 18th century Canadian population. Triennial Rep., 6,[8][9][10][11][12][13][14][15]. Pallast, E.G.M., Jongbloet, P.H., Straatman, H.M. and Zielhuis, G.A. (1994) Excess seasonality of births among patients widi schizophrenia and seasonal ovopathy. Schizophr. Bull., 20, 269-276. Philpot, M., Rottenstein, M., Bums, A. and Der, G. (1989) Zielhuis, G.A. and Jongbloet, P.H. (1996) Seasonal variation in the time to pregnancy; avoiding bias by using the date of onset. Epidemiology, in press. Troya, M., Bomsel-Helmreich, O., Bertrand, P., Papiemik, E. and Spira, A. (1985) Relationship between the characteristics of the menstrual cycle and congenital malformations in the human. Early Hum. Develop., 11, 307-315. Weinberg, C.R., Baird, D.D. and Wilcox, AJ. (1995) The sex of the baby may be related to the length of the follicular phase in the conception cycle.

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Section: Interpregnancy Intervals High Maternal Age and Seasonal Effmentioning

confidence: 99%

Further concepts on regulators of the sex ratio in human offspring: Interpregnancy intervals, high maternal age and seasonal effects on the human sex ratio

James¹

1996

Human Reproduction

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“…Those with durations of [40][41][42] weeks contain almost exactly equal numbers of males and females (James 1994). In that paper, I argued that this phenomenon was a (much-damped) consequence (roughly nine months later) of the regression of sex ratio on time of insemination within the cycle.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

“…twc > DOG. This entailment relationship is based on the demonstration (James 1994) (using a simple model) that the U-shaped regression of sex ratio on time of insemination potentially generates the established reverse-J-shaped regression of sex ratio on duration of gestation. The point needs further testing by computer modelling.…”

Section: Acknowledgmentsmentioning

confidence: 99%

The variances of the distributions of the combinations of the sexes within mammalian litters: Notes to mark the centenary of the problem

James

2009

Journal of Theoretical Biology

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“…There were 171 females born after more than 42 weeks of gestation, but only 161 male babies. Thus, there was not, as James (1994) had stated, a U-shaped curve when the sex ratio of births was plotted against duration of gestation. Jongbloet et al (1996) are correct in stating that the interval before a male birth is shorter than the interval before a female birth, something I had reported in 1958 and since confirmed by Renkonen and Lehtovaara (1962) and others.…”

Section: Gestation Length and Sex Of Childmentioning

confidence: 99%

“…He used in an earlier paper on this subject (James, 1994), data derived from US census data. However, these data are very imprecise; much better data on length of gestation are available (Koller, 1983) from a study of 6793 pregnancies in order to determine different risk factors.…”

Section: Gestation Length and Sex Of Childmentioning

confidence: 99%

Effects of agonist dose on in-vitro fertilization

Lashen¹,

Ledger²

1998

Human Reproduction

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Effects of agonist dose on in-vitro fertilizationDear Sir, Alvarez et al. (1997) have made a useful contribution to this field of research. However, there are possible alternative interpretations for their findings which we feel might be usefully considered. Their study appears flawed in that there are no data concerning concentrations of follicle stimulating hormone (FSH) on day 3 of the cycle, or on previous pregnancies and their outcomes -both features are important when assessing outcome variables. In our experience, we also find that obese patients require significantly longer duration to achieve down-regulation, using the same criteria as the authors, but this has no impact on pregnancy rate.Finally, and most importantly, the chosen cut-off point of 13 days duration of gonadotrophin-releasing hormone (GnRHa) administration was not justified in their manuscript. We find this biased, since in their small sample shifting two patients from GII (longer duration) to GI (shorter duration) by choosing a cut-off of 14 or 15 days can lead to no significance in the pregnancy rate between the two groups. To demonstrate this statistically we carried out the following exercise: the reported pregnancy rates in the study for GI and GII were 44 and 20% respectively which is 9/27 and 12/45. Using the c 2 test gives P ϭ 0.027. By increasing the cut-off point by 1 or 2 days the pregnancy rates may be: 12/43 and 9/29 (assuming no change in the number of the pregnant patients) which makes P ϭ 0.06, (not significant). Furthermore, the authors did not indicate how often they measured the patients serum oestradiol to verify the concentrations Ͻ50 pg/ml. This has to be on a daily basis so that the cut-off point may be in days. However, every other day or weekly measurement of oestradiol does not give accurate duration in days. On the other hand, as the authors indicated in their study, the patients were seen in the first few days of their period for ultrasound scan and oestradiol measurement. Since their measurements were not on a specific day, inadvertent over-estimation of the days of GnRHa administration could not be ruled out. In conclusion, we feel that a prospective study is necessary to address these issues effectively. Care must be taken in over-interpreting data collected from small numbers.Reference Alvarez, C., Cremades, N., Blasco, N. and Bernabeau, R. (1997) (Alvarez et al., 1998). In response to this comment we would like to clarity that patients were separated into two groups according to the number of days of agonist administration, and the value of the median (13 days) was chosen as a cut-off point. When we chose other cut-off points (12 or 14 days), the pregnancy rate per cycle and per transfer was significantly lower in the patients group suppressed for a longer period (Neyro et al., 1994) (Tables I and II).Ovarian quiescence was verified for the first or second day of cycle with no follicular growth observed by transvaginal ultrasound and an oestradiol serum concentration of Ͻ50 pg/ml on the same day. Cer...

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Cycle day of insemination, sex ratio of offspring and duration of gestation

Cited by 33 publications

References 9 publications

Further concepts on regulators of the sex ratio in human offspring: Interpregnancy intervals, high maternal age and seasonal effects on the human sex ratio

Further concepts on regulators of the sex ratio in human offspring: Interpregnancy intervals, high maternal age and seasonal effects on the human sex ratio

The variances of the distributions of the combinations of the sexes within mammalian litters: Notes to mark the centenary of the problem

Effects of agonist dose on in-vitro fertilization

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