Matsuo Koji, Ushioda Norichika, Udoff Laurence C
Obstetrics, Gynecology, and Reproductive Sciences, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
J Obstet Gynaecol Res. 2009 Feb;35(1):164-8. doi: 10.1111/j.1447-0756.2008.00836.x.
The aim of this study was to investigate the effect of parental age as a factor in the observed decline in the male to female birth ratio expressed as the offspring sex ratio (OSR).
A prospective multicenter study was conducted from August 2005 to February 2007 at five community-based hospitals in Osaka, Japan. Pregnant women in the first trimester were recruited at their first prenatal care visit and followed until delivery. Multiple pregnancies and assisted conceptions were excluded. Periconceptional parental ages were recorded. Neonatal information was obtained at the time of delivery. Proportional distribution of categorical variables was studied using the chi(2) or Fisher's exact tests (two-tailed).
Data on 3,049 deliveries were available for review. OSR for the largest paternal and maternal subgroup (both, age 30-34) were male dominant (1.17 and 1.12, respectively). Paternal age > or =40 showed a smaller OSR (0.75 vs 1.17, P = 0.001). Advanced maternal age was associated with smaller OSR: age 35-39, 0.87 versus 1.12, P = 0.02; and age > or =40, 0.63 versus 1.12, P = 0.047. Synergistic effects of increasing paternal and maternal age on the OSR were observed. OSR for parental ages > or =40 were significantly smaller than ages 30-34 (0.52 vs 1.17, P = 0.029).
Increasing paternal ages synergistically decrease the male to female birth ratio.
本研究旨在调查父母年龄作为一个因素对观察到的以子代性别比（OSR）表示的男女出生性别比下降的影响。
2005年8月至2007年2月在日本大阪的五家社区医院进行了一项前瞻性多中心研究。孕早期的孕妇在首次产前检查时被招募，并随访至分娩。排除多胎妊娠和辅助受孕情况。记录受孕时父母的年龄。在分娩时获取新生儿信息。使用卡方检验或Fisher精确检验（双侧）研究分类变量的比例分布。
有3049例分娩的数据可供审查。父母年龄最大的亚组（父母双方年龄均为30 - 34岁）的OSR以男性为主（分别为1.17和1.12）。父亲年龄≥40岁时OSR较小（0.75对1.17，P = 0.001）。母亲年龄较大与较小的OSR相关：35 - 39岁，0.87对1.12，P = 0.02；≥40岁，0.63对1.12，P = 0.047。观察到父母年龄增加对OSR有协同作用。父母年龄≥40岁时的OSR显著低于30 - 34岁时（0.52对1.17，P = 0.029）。
父亲年龄增加会协同降低男女出生性别比。
