Season of birth influences the timing of first menstruation

Abstract

The present data suggest that the season of birth influences sexual maturation rate in women.

Age at menarche in relation to prenatal rainy season exposure and altitude of residence: results from a nationally representative survey in a tropical country

“…9,10,[21][22][23][24] One recent study among 1,697 Polish women found that those who were born during summer months (June to August) reported an average age at menarche that was 0.1, 0.3 and 0.2 years earlier than did women born during fall, winter and spring, respectively (P < 0.01). 9 In another study among 950 women from the United States, those born in February had an average age at menarche that was 0.5 years earlier than the menarche of women born in December (P < 0.04). 10 This difference was only statistically significant when the analyses were restricted to women born before 1970.…”

“…For example, the seasonal incidence of respiratory infections could be more marked at higher elevations. 9 It is also plausible that cooler overall temperatures at high altitudes are correlated with greater differences in seasonal behavior among pregnant women, which could affect exposure to sunlight (e.g. through clothing choices).…”

“…Accelerating the timing of sexual maturation could constitute one of those adaptations. Some studies conducted in temperate climates found associations between the season of birth and onset of puberty in the offspring 9 10 For example, a study among Polish women reported a slightly earlier mean age at menarche among those born in summer compared with those born in other seasons (13.1 years for summer-born women v. 13.4 years for winter-born, 13.3 years for spring-born, and 13.2 years for fall-born; P <0.01) 9 .…”

Season of birth is not associated with age at menarche in young adults from Central India

“…Researchers have noticed that age at menarche can be associated with the season of birth, or more accurately with seasonal differences in temperature, humidity, sunlight, rainfall, affecting the fetus in utero (Dossus et al, ; Kersemaekers et al, ; Kliś et al, ). The state of Madhya Pradesh is influenced by a sub‐tropical climate with a hot‐dry summer (April‐June) followed by the monsoon season (June‐September).…”

Birth weight and prepubertal body size predict menarcheal age in India, Peru, and Vietnam

“…In the Northern hemisphere, previous research suggested that menarche peaks in winter or summer as compared with autumn and spring . We leave the investigation on the relationship between month and season at birth and age at menarche, which was also studied in the context of the Northern hemisphere, to future research. On the other hand, compared with other studies that asked adult women to retrospectively recall their age at menarche, often many years later, we anticipate that recall bias for menarcheal age in our data should be relatively lower, given the relatively short time span between the occurrence of menarche and the interview date.…”