Poster session IV Academic issues, epidemiology, global maternal-fetal public health, infectious diseases, intrapartum fetal assessment, operative obstetrics| Volume 201, ISSUE 6, SUPPLEMENT , S211, December 2009

568: The Chinese birth calendar for prediction of gender - fact or fiction?


      To evaluate the accuracy of the Chinese birth calendar in predicting infant gender.

      Study Design

      We performed a retrospective database review of prenatal and delivery records of all singleton deliveries at Massachusetts General Hospital between January 1st, 1995 and June 30th, 2008. Pregnancies complicated by multiple gestations and infants with ambiguous genitalia were excluded from analysis. Predicted infant gender based on month of conception and maternal age was compared to infant gender at birth in 38, 394 delivery records. Gestational age was determined by last menstrual period if available or by first available ultrasound. Date of conception was assumed to be 14 days post the first day of the last menstrual period. Month of conception was calculated by subtracting gestational age in days at time of delivery from the date of delivery. Maternal age was calculated based on both the Chinese lunar calendar and the Gregorian calendar for comparison.


      Of the 38394 deliveries at MGH, 18683 (48.66%) were females and 19711 (51.34%) were males. 19 infants had ambiguous genitalia and were excluded. Accurate prediction of fetal gender based on the mother's Gregorian calendar age occurred in 19346/38394 (50.4%). Using the mother's Chinese lunar age, accurate prediction of fetal gender occurred in 19406/38394 (50.2%).


      The Chinese birth calendar claims 93-99% accuracy in predicting infant gender based on month of conception and maternal age at delivery. In this large delivery dataset, accurate prediction of fetal gender based on the Chinese birth calendar was no better than a coin toss. Our study is limited by inclusion of pregnancies resulting from artificial reproductive technologies.