李东璧曰∶《易》云∶男女构精，万物化生；干道成男，坤道成女。褚澄言血先至裹精则生男；精先至裹
血则生女；阴阳均至，非男非女之身；精血散分，骈胎品胎之兆。道藏言月水无后，一、三、五日成男，二、
四、六日成女。东垣言血海始净，一、二日成男，三、四日成女。圣济言因气而左动，阳资之则成男；因气而
右动，阴资之则成女。丹溪乃非褚氏而是东垣，主圣济左右之说立论，归于子宫左右之系，可谓悉矣。窃谓褚
氏未可非，东垣亦未尽是也。盖褚氏以气血之先后言；道藏以日数之奇偶言；东垣以女血之盈亏言；圣济、丹
溪以子宫之左右言。各执一见，会而通之，理自得矣。盖独男、独女，可以日数论，骈胎、品胎，亦可以日数
论乎？史载一产三子、四子，有半男、半女，或男多、女少，或男少、女多，则一、三、五日为男，二、四、
六日为女之说，岂其然哉？褚氏、圣济、丹溪，主精血
子宫左右之论为有见，而道藏、东垣日数之论为可疑矣。王叔和《脉经》，以脉之左右浮沉，辨所生之男女；
高阳生《脉诀》，以脉之纵横逆顺，别骈品之胎形∶恐臆度之见，非确论也。
王孟英按∶阅《微草堂笔记》云∶夫胎者，两精相搏，翕合而成者也。媾合之际，其情既洽，其精乃
至。阳精至而阴精不至，阴精至而阳精不至，皆不能成；皆至矣，时有先后，则先至者气散不摄，亦不能
成。不先不后，两精并至，阳先冲而阴包之，则阳居中为主而成男；阴先冲而阳包之，则阴居中为主而成
女。此生化自然之妙，非人力所能为。故有一合即成者，有千百合而终不成者，愚夫妇所知能，圣人有所
不知能，此之谓矣。端恪后人沈君辛甫云∶胎脉辨别处，诚医者所当知。若受妊之始，曷以得男，何缘得
女，生化之际，初无一定。诸家议论虽奇，无关损益，置之可也。
李东璧说：《易经》讲：男女交合，万物化生；天道成就男性，地道成就女性。褚澄说：如果女性的血先到达并包裹男性的精，则生男孩；如果男性的精先到达并包裹女性的血，则生女孩；如果阴阳（精血）同时到达，则可能生出非男非女的身体；如果精和血分散分布，则是双胎或多胎的征兆。道藏记载：月经结束后的一、三、五天受孕成男，二、四、六天受孕成女。李东垣说：在血海刚刚干净时，一、两天受孕成男，三、四天受孕成女。《圣济总录》说：如果气向左动，由阳资助则成男；如果气向右动，由阴资助则成女。朱丹溪否定褚氏的观点而赞同李东垣，主张《圣济总录》关于左右之说，将其归结为子宫左右系带的关系，可以说详尽无遗了。但我认为褚氏不可轻易否定，李东垣也未必完全正确。大概褚氏是从气血到来的先后顺序来说的；道藏是从日数的奇偶性来说的；李东垣是从女子经血的盈亏状态来说的；圣济、丹溪是从子宫的左右位置来说的。各自坚持自己的见解，如果能融会贯通，道理自然明了。难道只有单胎的男或女，可以用日数来论断吗？双胎、多胎，也可以用日数来论断吗？史书记载一次分娩三个孩子、四个孩子的情况，有半男半女，或者男多女少，或者男少女多，那么“一、三、五日为男，二、四、六日为女”的说法，难道是真的吗？褚氏、圣济、丹溪，主张精血与子宫左右关系的观点是有见地的，而道藏、李东垣关于日数的观点是值得怀疑的。王叔和在《脉经》中，通过脉象的左右浮沉，来辨别所生胎儿的性别；高阳生在《脉诀》中，通过脉象的纵横逆顺，来区别双胎或多胎的形态：恐怕这些是主观臆测的看法，并非确切的论述。
王孟英按语：阅读《微草堂笔记》说：胎儿，是两精相搏，融合而成的。在交合之际，情意既已融洽，精气才至。如果阳精到了而阴精没到，或者阴精到了而阳精没到，都不能形成胎儿；如果都到了，但时间有先后，那么先到者的气会散失而不能摄持，也不能形成胎儿。如果不分先后，两精同时到达，阳先冲击而阴包裹它，则阳居中为主而成男；阴先冲击而阳包裹它，则阴居中为主而成女。这是生化自然的奥妙，不是人力所能做到的。所以有的交合一次就成胎，有的交合千百次却始终不成胎，这是普通夫妇所知能做到的，圣人也有不知道做不到的地方，说的就是这个道理。端恪的后人沈辛甫先生说：胎脉的辨别之处，确实是医生应当知道的。至于怀孕之初，为何得男，因何得女，在生化之际，起初并没有一定的规律。各家议论虽然奇特，但对临床没有实际损益，放置一边即可。
Li Dongbi said: The *I Ching* (Book of Changes) states: "When male and female combine their essence, all things are transformed; the Way of Heaven forms the male, and the Way of Earth forms the female." Chu Cheng stated: If the blood arrives first and envelops the essence, a male is born; if the essence arrives first and envelops the blood, a female is born; if yin and yang (essence and blood) arrive simultaneously, it may result in a body that is neither male nor female; if essence and blood are scattered separately, it indicates the sign of twins or multiple fetuses. The Daoist Canon records: Conceiving on the 1st, 3rd, or 5th day after menstruation ends results in a male; conceiving on the 2nd, 4th, or 6th day results in a female. Li Dongyuan stated: When the Blood Sea (Chong Mai) has just cleared, conceiving on the 1st or 2nd day results in a male; on the 3rd or 4th day, a female. The *Shengji Zonglu* (General Records of Sage Relief) states: If Qi moves to the left and is nourished by Yang, a male is formed; if Qi moves to the right and is nourished by Yin, a female is formed. Zhu Danxi refuted Chu’s theory and supported Dongyuan’s, basing his argument on the *Shengji Zonglu*'s theory of left and right, attributing it to the ligaments of the left and right sides of the Uterus (Zigong). This can be considered thorough. However, I suggest that Chu’s view should not be dismissed, nor is Dongyuan’s entirely correct. Chu spoke from the perspective of the sequence of Qi and Blood arrival; the Daoist Canon spoke from the parity of days; Dongyuan spoke from the fullness or emptiness of menstrual blood; Shengji and Danxi spoke from the left-right position of the Uterus. Each adheres to one viewpoint; if they are integrated and understood together, the principle will naturally become clear. Can only single males or females be determined by days? Can twins or multiples also be determined by days? Historical records mention births of three or four children at once, with combinations of half male/half female, more males/fewer females, or fewer males/more females. Thus, is the saying "1st, 3rd, 5th days for males, 2nd, 4th, 6th days for females" really true? The views of Chu, Shengji, and Danxi regarding the relationship between essence/blood and the left/right of the Uterus are insightful, whereas the day-count theories of the Daoist Canon and Dongyuan are questionable. Wang Shuhe’s *Mai Jing* (Pulse Classic) distinguishes the sex of the fetus by the floating/sinking pulse on the left or right; Gao Yangsheng’s *Mai Jue* (Pulse Mantra) distinguishes twin/multiple fetal shapes by the crisscrossing/reverse pulse qualities: these are likely subjective speculations, not definitive arguments.
Wang Mengying added: Reading the *Weicaotang Biji* (Notes from the Micro Grass Hall), it says: A fetus is formed when two essences interact and merge. During intercourse, when emotions are harmonious, the essence arrives. If Yang essence arrives but Yin essence does not, or vice versa, conception cannot occur. If both arrive but at different times, the one arriving first loses its Qi and fails to grasp, so conception also fails. If neither is early nor late, and both essences arrive simultaneously, if Yang rushes forward first and Yin envelops it, Yang stays central as the master and forms a male; if Yin rushes forward first and Yang envelops it, Yin stays central as the master and forms a female. This is the wonder of natural biological transformation, beyond human control. Therefore, some conceive upon a single union, while others may unite thousands of times without success. This is what ordinary people know and can do, yet even sages may not know or be able to do—it refers to this phenomenon. Shen Xinpu, a descendant of Duanke, stated: The differentiation of fetal pulses is indeed knowledge physicians must possess. However, regarding whether one gets a male or female at the beginning of pregnancy, there is no fixed rule in the process of biological transformation. Although various discussions are ingenious, they have little practical clinical value and can be set aside.