生男生女并不随机！哈佛大学最新发现：母亲年龄和基因，会影响孩子性别

Core Findings - The study reveals a "same-sex clustering" phenomenon in families with multiple children, challenging the traditional view that each child's gender is an independent event with a 50% probability for boys and girls [3][4][5][7] - For families with three or more children, the likelihood of having all boys or all girls is higher than having both genders [7] - The probability of a woman having another boy after already having one boy is 57%, and this probability increases to 61% after having three boys. Similarly, the probability of having another girl after having one girl is 53%, increasing to 58% after three girls [4][5] Maternal Age Influence - The research indicates that a mother's age at the time of her first childbirth significantly affects the gender of her children. Women who give birth after the age of 29 have a 13% higher probability of having only boys or only girls compared to those who give birth before age 23 [9][10] - This suggests that the maternal environment, which changes with age, may influence the success of sperm carrying X or Y chromosomes [10] Genetic Factors - The study identifies specific genes associated with a tendency to give birth to boys or girls. A particular SNP (rs58090855) on chromosome 10 is linked to a higher likelihood of having girls, while another SNP (rs1506275) near the TSHZ1 gene on chromosome 18 is associated with a higher likelihood of having boys [12][13] - This indicates that some women may have a genetic predisposition that affects the gender ratio of their offspring, providing a new perspective on family gender patterns [13] Conclusion - Overall, the research demonstrates that the gender of newborns is not entirely random, with maternal age and specific genetic mutations playing significant roles in determining offspring gender [14][15] - The findings open new avenues for exploring the complex biological mechanisms influencing gender determination, while emphasizing that the study's purpose is to reveal natural patterns rather than to facilitate gender selection [15][16]