Menstrual characteristics of mothers of twins

Social, biological and reproductive characteristics of mothers of twins: implications for breast cancer risk

The biological, social and reproductive characteristics of women who have had twins were compared with those of other parous women using questionnaire data gathered for a prospective cohort study of women aged 35 and over on the island of Guernsey. Data for 97 mothers of twins and 4026 other parous women were available for analysis. The two groups were similar in height, first degree family history of breast cancer, use of hormone replacement therapy or other hormones, age at menarche, length of menstrual cycle and age at first and last birth. The mothers of twins were slightly heavier, more likely to smoke and consume more caffeine, less likely to have used oral contraceptives in the past, slightly younger when reaching the menopause and had a larger number of pregnancies. Adjustment for age did not alter these results. This study does not provide evidence that mothers of twins differ markedly from other parous women across a range of characteristics that might be associated with twinning or associated with breast cancer risk.

Menstrual disorders and month of birth

Menstrual characteristics in a population of 23,227 women who participated in a breast cancer screening programme were considered with respect to month of birth. High and low risk months of birth were defined according to the seasonal preovulatory overripeness ovopathy (SPrOO) hypothesis. Positive associations were found in 11 out of the 14 relations studied. The results were significant for early menarche (< or = 11 years), long menstrual cycles (> or = 5 weeks), menorrhagia (> or = 7 days and profuse blood loss), and early (< or = 40 years) or late (> or = 56 years) menopause. The results not only confirm the birth excess of these women in specific months, as has been found by others. They apparently agree with the SPrOO hypothesis and with a transgenerational concept of familial subfecundability along matrilineal lines and hence, familial clustering of pathological progeny, independent of Mendelian rules.

The hypothesized hormonal control of human sex ratio at birth--an update

I have reviewed the literature on the human sex ratio at birth (W.H. James, 1987 a. Hum. Biol. 59, 721), and proposed a hypothesis to account for its variation (W.H. James, 1987 b. Hum. Biol. 59, 873). Since submitting those papers, some sets of data have been published which bear on the hypothesis and on how it may be tested. In this note some comments are made on these new data sets. The hypothesis proposes that hormone levels of both parents at the time of conception affect the sex of the resulting zygotes. This suggestion is unlikely to gain wide credence unless and until it has been demonstrated that sex ratios can thus be manipulated in experimental animals. This paper is offered in the hope that it may prompt workers to try testing the hypothesis in whatever way is open to them.