Concentrations of Sex Hormones in Umbilical-Cord Blood: Their Relation to Sex and Birth Order of Infants

Abstract

In 3 groups of human newborns, 5 sex hormones were assayed from samples of umbilical-cord blood, and concentrations were analyzed by the sex and birth order of the infants. The 5 hormones assayed were testosterone, androstenedione, estrone, estradiol, and progesterone. Concentrations of testosterone were significantly greater in males than females. The other 4 hormones did not differ significantly by sex. In both sexes, firstborns had significantly more progesterone and estrogens, with progesterone showing the largest birth-order effects. Among male infants, firstborns had higher concentrations of testosterone. The higher concentrations of progesterone in firstborns of both sexes, and of testosterone in firstborn boys, were found not to be due to length of labor, birth weight, or maternal age. However, they were a function of temporal spacing of childbirths. Later borns who were closely spaced in relation to their next-older siblings had lower concentrations of hormones. The effect of temporal separation was greater on male than female infants for each of the 5 hormones studied. The results are discussed in terms of the possible effects of hormone "depletion" on the psychological development of closely spaced later borns.

Gender of Offspring and Maternal Risk of Invasive Epithelial Ovarian Cancer

“…Findings on testosterone have been less consistent: levels in maternal and cord serum at term were not shown to be significantly different by offspring gender in some studies (43,47), whereas higher maternal and amniotic fluid levels in male bearers were found in others (48,49). Progesterone levels in maternal and fetal blood tend to be higher in male bearers than female bearers, although the difference was not significant (43,50). Studies that measured 17-hydroxyprogesterone, a metabolite of progesterone, have found significantly higher blood levels in males than in female newborns (51), particularly among the full-term deliveries (52).…”

What has high fertility got to do with the low birth weight problem in Africa?

“…A possible reason for this negative effect of birth order on the birth weight is that the mother's health may have been weakened as a result of many pregnancies and years of caring for children. This idea is somewhat medically supported in that it is believed that the growth of the baby during pregnancy is affected by the mother's levels of hormones and insulin-like growth factors; which tend to reduce at very high parities (D'Ercole and Ye 2008; Skalkidou et al 2003;Beyer 1999;Reece et al 1994;Panagiotopoulou et al 1990;Maccoby et al 1979).…”

Birth spacing and maternal risk of invasive epithelial ovarian cancer in a Swedish nationwide cohort

“…Based on findings indicating that levels of circulating progesterone increase with longer time between births, the present study tested whether the wider birth spacing for a given parity reduces the risk of ovarian cancer. With repeated pregnancies and close spacing between births, time may be too short for the recovery of certain maternal physiological processes involved in gestation and, as a result, the placenta may not be as active in producing progesterone [17].…”

“…Instead, the association with certain reproductive factors that reflect circulating levels of progesterone during pregnancy has been examined to lend indirect support and several epidemiologic studies have shown a greater risk reduction of epithelial ovarian cancer for the first birth than for subsequent births [2][3][4][5][7][8][9][10]. These findings are compatible with the physiological observation that first-born infants have higher progesterone levels in umbilical cord blood than later-borns [17].…”

“…Maccoby et al [17] found that, among the later-born infants, progesterone levels in umbilical cord blood increased with wider birth spacing, and was closer to or even higher than firstborns. They also found that this phenomenon is more noticeable in later-born male offspring.…”