Sex ratio is remarkably constant.Ein-Mor E, Mankuta D, Hochner-Celnikier D, Hurwitz A, Haimov-Kochman R.

1: Fertil Steril. 2009 Jan 19. [Epub ahead of print]
Sex ratio is remarkably constant.Ein-Mor E, Mankuta D, Hochner-Celnikier D, Hurwitz A, Haimov-Kochman R.
Department of Obstetrics and Gynecology, Hadassah Hebrew University Medical Center, Jerusalem, Israel.

OBJECTIVE: To study whether the sex of the offspring is related to increasing parental age, gravidity, and parity, hypothesizing an altered male-to-female sex ratio with the advancing parental age. DESIGN: A large retrospective cohort study. SETTING: The study analyzed birth records of Hadassah Hebrew University Medical Center in Jerusalem from June 2003 to December 2006. PATIENT(S): 35,837 birth records were analyzed including 941 multifetal deliveries, excluding foreign inhabitants (n = 744), missing data for the main study outcome (n = 2) and parturients over 50 years to control for egg donation (n = 26). INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Male-to-female sex ratio. RESULT(S): The male-to-female sex ratio of all the newborns was 1.05. This ratio did not change significantly with either maternal or paternal age. Neither gravidity nor parity affected the male-to-female ratio. The only factor that affected the regression of sex ratio was the length of gestation. CONCLUSION(S): Sex ratio at birth is remarkably constant. No association was found between parental age or birth order and neonatal sex ratio.

PMID: 19159875 [PubMed - as supplied by publisher]

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