Human Reproduction, Vol. 16, No. 8, 1777,
August 2001
© 2001 European Society of Human Reproduction and Embryology
Letters to the editor |
Blood pressure during pregnancy, sex ratio of offspring and reproductive hormone concentrations
The Galton Laboratory, University College London, Wolfson House, 4 Stephenson Way London NW1 2HE, UK
Dear Sir,
Kristiansson and Wang report an inverse relation between progesterone concentrations at 8–10 weeks of pregnancy in the 2nd and 3rd trimesters of pregnancy (Kristiansson and Wang, 2001
). I have summarized data on the sexes of offspring of women with conditions variously described as `toxaemia', `eclampsia', `pre-eclampsia' and `pregnancy-induced hypertension' (James, 1995). It is clear that in one or more of these categories there is a statistically significant excess of males among the associated offspring. It has been suggested that this excess is restricted to hypertensive—as opposed to proteinuric—cases (Campbell et al.1983).
I have adduced substantial quantities of evidence to support the hypothesis that the sexes of mammalian (including human) offspring are associated with the ratio R, where R is of the form (E+T)/(G+P), where E, T, G and P are respectively the parents' sex-standardized concentrations of oestrogen, testosterone, gonadotrophins and progesterone (James, 1996).
In my 1995 paper, I offered grounds for supposing that pregnancy-induced hypertension is associated with high maternal oestrogen and/or testosterone concentrations. These suggestions are supplemented by Kristiansson and Wang's finding of low progesterone at 8–10 weeks. This is so because if one may assume that a woman's progesterone concentration early in pregnancy is an index of her progesterone concentration at conception, then these authors' finding is also compatible with my hypothesis, as will be seen from the formula above. All these speculations could be tested by examining the extent to which infiltration by extravillous trophoblast into the placental bed is controlled by these hormones.
References
Campbell, D.M., MacGillivray, I., Carr-Hill, R. and Samphier, M. (1983) Foetal sex and pre-eclampsia in primigravidae. Br. J. Obstet. Gynaecol., 90, 26–27.[Web of Science][Medline]
James, W. H. (1995) Sex ratios of offspring and the causes of placental pathology. Hum. Reprod., 10, 1403–1406.
James, W. H. (1996) Evidence that mammalian sex ratios at birth are partially controlled by parental hormone levels at the time of conception. J. Theor. Biol., 180, 271–286.[Web of Science][Medline]
Kristiansson, P. and Wang, J.X. (2001) Reproductive hormones and blood pressure during pregnancy. Hum. Reprod., 16, 13–17.
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