褚澄氏曰∶男女交合，阴血先至，阳精后冲而成男，反则成女，此一说也。
东垣云∶经水才断一二日，血海始静，交合成男。四五日后，血脉已旺，交合成女，此又一说也。顾或有
经始断，而交合生女，经久断而交合生男者。亦有三五日交合无孕，八九日交合有孕者，独何与。
《广嗣要略》云∶实阳能入虚阴，实阴不能受虚阳也。又谓∶阳微不能射阴，弱阴不能摄阳，信斯言也。
世有 羸之夫，怯弱之妇，屡屡受胎，虽欲止而不能止者，亦有壮年精力过人，乃艰于嗣育者，独何欤。
丹溪曰∶妇人以经水为主，然富贵之家侍外家既多，其中岂无月水当期者乎，有已经前夫频频生育，取之以
图其易者，顾亦不能得胎，更遣与他人，转 亦生男矣。岂不能受孕于此，而能受孕于彼乎。
本立曰∶父母之生子，如天地之生物。易曰∶坤道其顺乎，承天而时行，夫知地之生物不过顺承乎。天则
知母之生子，亦不过顺承乎，父而已知母之顺承乎。父则种子者，当以男子为主。男子为主而交媾之时，又以
百脉齐到为善，交媾能而百脉齐到，虽老弱易泄，亦可以成胎。若百脉参差，虽少壮康宁难泄，亦不能
成胎。若男女之辨，不以精血先后为拘，不以经尽几日为拘，不以夜半前后交媾为拘，只以男女精血，各
由百脉齐到者，别胜负耳，是故精之百脉齐到，有以胜乎血，则成男矣。血之百脉齐到，
有以胜乎精，则成女矣。至有产而不育者，有育而不能寿者，有
寿而黄 无疆者，则亦以精之坚脆分为修短耳。
褚澄说：男女交合时，如果阴血先到达，阳精随后冲击，就会生男孩；反之则生女孩，这是其中一种说法。
李东垣说：月经刚结束的一两天，血海（指冲脉，为血之海）刚刚平静，此时交合会生男孩；四五天之后，血脉已经旺盛，此时交合会生女孩，这又是另一种说法。但是，有的月经刚结束就交合生了女孩，有的月经结束后很久才交合却生了男孩。也有交合后三到五天没有怀孕，八九天交合反而怀孕的情况，这究竟是为什么呢？
《广嗣要略》说：阳气充实才能进入阴气虚弱的部位，阴气充实却不能接受阳气虚弱的部位。又说：阳气微弱不能射入阴中，阴气虚弱不能摄受阳气。相信这些话的话……世间有身体瘦弱衰败的男子和怯懦虚弱的妇女，却屡屡受孕，即使想停止也停不下来；也有正值壮年、精力过人的人，却难以生育子女，这又是为什么呢？
朱丹溪说：妇女以月经为主，然而富贵人家侍妾众多，其中难道没有月经按时来潮的吗？有的女子曾经被前夫频繁生育，娶过来是为了图容易受孕，结果也不能怀上胎；再转嫁给别人，反而生了男孩。难道她不能在此处受孕，却能在彼处受孕吗？
本立说：父母生子，就像天地化生万物。《易经》说：“地道柔顺，顺应天道而按时运行。”既然知道大地化生万物不过是顺应承接罢了。那么母亲生子，也不过是顺应承接父亲罢了。父亲则是种子的提供者，应当以男子为主导。以男子为主导，在交合之时，又以全身经脉之气同时到达为佳。交合时若能百脉齐到，即使是年老体弱容易泄精的人，也可以成胎。如果百脉之气参差不齐，即使是年轻力壮身体健康难以射精的人，也不能成胎。至于男女的辨别，不拘泥于精血到来的先后顺序，不拘泥于月经结束后的天数，也不拘泥于是否在半夜前后交合，只以男女双方的精血，各自由百脉齐到的情况，来辨别胜负罢了。因此，如果精气的百脉齐到胜过血气，就会生男孩；如果血气的百脉齐到胜过精气，就会生女孩。至于有出生后不养育的，有养育了但不能长寿的，有长寿但寿命无疆限的，这也是因为精气的坚固或脆弱决定了寿命的长短。
Chu Cheng stated: When man and woman engage in intercourse, if the Yin blood arrives first and the Yang essence follows to strike, a male child is conceived; if reversed, a female child is conceived. This is one theory.
Li Dongyuan said: One or two days after menstruation ceases, the Blood Sea (Chong Mai, the sea of blood) has just calmed down; intercourse at this time results in a male. Four or five days later, when the blood vessels are vigorous, intercourse results in a female. This is another theory. However, there are cases where intercourse immediately after menstruation yields a female, while intercourse long after menstruation yields a male. There are also instances where conception does not occur within three to five days of intercourse, but occurs eight or nine days later. Why is this so?
The *Guang Si Yao Lue* states: Solid Yang can enter Empty Yin, but Solid Yin cannot receive Empty Yang. It further says: Weak Yang cannot shoot into Yin, and weak Yin cannot grasp Yang. If one believes these words... In the world, there are emaciated men and timid, weak women who conceive repeatedly, unable to stop even if they wish to do so. Conversely, there are men in their prime with abundant vitality who struggle to have offspring. Why is this?
Zhu Danxi said: Women are primarily governed by menstruation. Yet, in wealthy households with many concubines, are there not some whose menstrual cycles are regular? Some women, having been frequently pregnant by a former husband, are taken for ease of conception, yet fail to conceive. If transferred to another man, she may conceive a male. Can it be that she cannot conceive with one man but can with another?
Ben Li said: The parents' generation of children is like Heaven and Earth generating all things. The *I Ching* states: "The way of Kun (Earth) is its submission, receiving from Heaven and acting according to the seasons." Knowing that Earth generates things merely by submitting and receiving, we know that a mother's bearing of children is also merely submitting and receiving from the father. The father is the sower of seeds, and thus should take the lead. With the father taking the lead, during intercourse, it is auspicious for the Qi of all meridians to arrive simultaneously. If the Qi of all meridians arrives simultaneously during intercourse, even an old or weak man prone to premature emission can achieve conception. If the Qi of all meridians is disordered, even a young, strong, and healthy man who finds it difficult to emit can fail to achieve conception. Regarding the determination of sex, one should not be bound by the sequence of essence and blood arrival, nor by the number of days since menstruation ceased, nor by whether intercourse occurs before or after midnight. Instead, one should distinguish victory based on which party's essence and blood, arriving via the simultaneous convergence of all meridians, prevails. Therefore, if the simultaneous convergence of essence's meridians prevails over blood's, a male is conceived. If the simultaneous convergence of blood's meridians prevails over essence's, a female is conceived. As for those born but not raised, those raised but not living long, or those living long without limit, these differences in lifespan are determined by the firmness or fragility of the essence.