Hoffmann F
Geburtshilfe Frauenheilkd. 1979 Mar;39(3):243-7.
Seasonal fluctuations in the sex ratio of new borns are investigated. The largest predominance of male deliveries over female deliveries was found to be during the conception months May-June with an almost constant number of deliveries. The highest value was in June. Seasonal maximum of the male to female sex ratio is concomitant to the seasonal maximum of conceptions. The investigation of the yearly sex ratio from 1958-1978 showed changes in the secondary sex ratio concomitant to the increase or decrease of the delivery rate. When the delivery rate decreased below 10 deliveries by 1000 population a reverse in the sex ratio was noted and the lowest number of male deliveries was found. This occurred although the number of first deliveries increased further with the decrease of multiparities. The reasons for this reverse trend in the sex ratio are discussed and a possible relationship to preceeding oral contraception is mentioned.
对新生儿性别比例的季节性波动进行了调查。发现男婴出生数相对于女婴出生数的最大优势出现在5月至6月的受孕月份，分娩数量几乎保持不变。最高值出现在6月。男女比例的季节性最大值与受孕的季节性最大值同时出现。对1958年至1978年年度性别比例的调查显示，随着分娩率的上升或下降，第二性征比例发生了变化。当分娩率降至每1000人口10例以下时，性别比例出现逆转，男婴出生数达到最低。尽管随着多胞胎数量的减少，初产数量进一步增加，但仍出现了这种情况。讨论了性别比例这种逆转趋势的原因，并提及了与之前口服避孕药可能存在的关系。
