Demography

, Volume 4, Issue 2, pp 673–679 | Cite as

Seasonality of coitus and seasonality of birth

  • J. Richard Udry
  • Naomi M. Morris
Article

Summary

Seasonal variation of birth rates has been observed in every population in which it has been studied. Many hypotheses have been advanced to account for the variation, including seasonal variation in frequency of coitus. This relationship is known to be true for other primates, but seasonal variation in coital rate has not been previously documented in man.

This paper presents over one hundred woman-years of data on coital rates from about .fifty white, mostly well-educated, premenopausal, married, husband-present volunteers. Seasonal fluctuations were seen in coital rates, of about the same magnitude as seasonal variations in the white birth rates reported for New York City, 1962–64; for the United States, 1963; and for the highest socioeconomic quintile census tracts, Baltimore, 1952–56. However, shifting the birth rates back forty weeks to approximate conception dates revealed no association with the observed coital rates.

If the pattern presented has great generality, seasonal variations in births cannot be explained by seasonality of coitus.

Resumen

En todas las poblaciones estudiadas se ha observado quehay una variación estacional en la tasade natalidad. Se han adelantado muchas hipótesis para explicaresiavariación, incluyendo una variación estacional en lafrecuenciadel coiio, Se sabe que ésta relación es eierta para otros primates, peroen el hombre, no se ha documentado anteriormente una variación estacional en la tasa de coiios.

Este trabajo presenia datos equivalentes a más deciem años-mujer sobre tasasde coito, correspondientes a cincuenta mujeres voluntarias, de rasa blanca, en su mayor parte bien educadas, en edad pre-menopáusica, casadas y conesposo presente. Se encontró que había fluctuaciones estocionales en las tasas de coito, más 0 menos de la misma magnitudque las variaciones estacionales en las tasasde nacimientos de blancos, que se han informado para la ciudad de New York 1962–1964; para los Estados Unidos 1963; y para el quintillo socioeconómico más alto de las divisiones zensalee, Baltimore, 1952–1956. Sinembargo al desplazar las tasae de nacimientos euarienta semanas para aproximarlas a las fechas de la conzepci6n, no se pudo demostrar alguna asociación con las tasas de coiio observadas.

Si el esquema presentado tiene posibilidades de generalización, las variaciones estacionales en los nacimientos no pueden ser explicadas por variaciones esiacionales en el coito,

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Copyright information

© Population Association of America 1967

Authors and Affiliations

  • J. Richard Udry
    • 1
  • Naomi M. Morris
    • 1
  1. 1.University of North CarolinaUSA

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