结胎者。男女精血也。男属阳而象干。干道资始。女属阴而象坤。坤道资生。阳主动。故能施与。
阴主静。故能承受。夫动静相参。阴阳相会。必有其时。乃成胎孕。凡经尽一日至三日。新血未盛。
精胜其血。血开裹精。精入为骨。男胎成矣。四日至九日。新血渐长。血胜其精。精开裹血。血入居本。
女胎成矣。六日至七日。鲜有成者。纵成亦皆女胎。欲求子者。全在经静三日以里交合。如俯首拾芥。
万举万当。斯时男女无暴怒。毋醉饱。毋食炙爆辛热。毋用他术赞益。阴阳和平。精血调畅。交而必孕。
孕而必育。育而为子。坚壮强寿。至真切要。在此数语。受妊之后。宜令镇静。血气安和。则胎孕长养。
又须内远七情。外薄五味。大冷大热之物。皆在所禁。苟无胎痛。胎动。漏血。泻痢。及风寒外邪。不可
轻易服药。亦不得交合阴阳。触动欲火。未产则胎动不常。既产则胎毒不已。降生之后。摄养一如胎前。
盖母食热则乳热。母食寒则乳寒。母食膏粱舋烈之物。则乳毒。有是数者。子受其害矣。求嗣之道。诚
不出此。然源头一节。尤当研究。男子十六而精通。必三十而娶。女子十四而天癸至。必二十而嫁。皆欲
阴阳二气完实。或精未通而御女。经始至而近男。未完而伤。未实而动。根本既薄。枝叶必衰。嗣续岂
能蕃衍。先儒尝言。寡欲则有子。盖寡欲则不妄交合。积气储精。待时而动。故能有子。愚谓不止此为寡欲。
凡心有所动。即是欲。心主血而藏神。属手少阴。肾主精而藏志。局足少阴。心神外驰。则肾志内乱。其
于交会之际。殊无静一清宁之气。所泄之物。同归腐浊而已。安能发育长养于其间哉。书曰。人心惟危。道心
惟微。夫能精一道心。俾常为一身之主。则邪思妄念。自尔退听。欲寡而神益完。不惟多子。抑且多寿。
盖养生尤贵于寡欲故也。
受孕成胎，源于男女双方的精与血。男性属阳，象征乾卦（代表天、刚健），乾道创始万物；女性属阴，象征坤卦（代表地、柔顺），坤道孕育生命。阳主动，所以能够施予精气；阴主静，所以能够承受精气。动与静相互参合，阴与阳相互交会，必须把握恰当的时机，才能形成胎孕。
通常在月经结束后的第一至第三天，新产生的血液尚未旺盛，此时男子的精气胜过女子的经血。精气打开并包裹住血液，精气进入成为骨骼的基础，男胎便形成了。第四至第九天，新血逐渐生长，此时血液胜过精气。血液打开并包裹住精气，血液居于根本位置，女胎便形成了。第六至第七天，极少能受孕成功，即使成功也多为女胎。想要求子的夫妇，完全在于月经干净后三天内行房事，这就像低头捡取地上的草芥一样容易，每次尝试都能准确命中。在这个时期，男女双方都不要有暴怒情绪，不要醉酒饱食，不要吃烤炸及辛辣燥热的食物，也不要使用其他方法辅助助益。做到阴阳平和，精血调畅，交合必定怀孕，怀孕必定顺利养育孩子，生下的孩子也会坚固强壮、健康长寿。最为真切重要的道理，就在这几句话中。
受孕之后，应当保持心境镇静，使气血安和，这样胎孕才能正常生长发育。同时必须在内远离七情（喜、怒、忧、思、悲、恐、惊）的过度干扰，在外避免接触过于浓烈的五味饮食以及大冷大热的食物，这些都是禁忌。如果没有胎痛、胎动不安、漏血、腹泻痢疾以及风寒外邪侵袭等症状，不要轻易服药。也不得进行房事，以免触动欲火。未分娩前若频繁房事会导致胎动无常，产后若纵欲则胎毒难清。婴儿降生之后，喂养护理要像对待胎儿时期一样谨慎。因为母亲吃热性食物乳汁就变热，母亲吃寒性食物乳汁就变寒，母亲吃油腻厚味及气味烈性的食物，乳汁就会产生毒素。有了这些情况，孩子就会受到危害。求子的道理，确实离不开这些原则。然而关于源头这一节，尤其需要深入研究。
男子十六岁时精气通畅，但一定要等到三十岁才娶妻；女子十四岁时天癸（指促进生殖机能成熟的物质）已至，但一定要等到二十岁才出嫁。这都是为了让阴阳二气完备充实。如果在精气尚未通畅时就御女行房，或在月经初来时就亲近男子，身体未发育成熟就受损伤，元气未充实就妄动，根本既然薄弱，枝叶必然衰败，子嗣怎么能繁衍兴盛呢？先前的儒者曾说，节制欲望就能有子嗣。大概是因为节制欲望就不会胡乱交合，从而积聚气机、储存精气，等待合适的时机再行动，所以能有子嗣。我认为不止于此才是寡欲，凡是心中有所萌动，就是欲望。心主血而藏神，归属于手少阴心经；肾主精而藏志，归属于足少阴肾经。如果心神向外驰散，那么肾志就会在内部混乱。在交合之际，完全没有清净安宁的气机，所排出的精液也就同归于腐败浑浊罢了，怎么能在其中发育滋养生命呢？《尚书》说：“人心危险难保，道心微妙难明。”如果能专精于道心，使其常作为一身之主，那么邪恶的念头自然退避听从。欲望减少而精神更加完备，不仅多子，而且长寿。大概养生特别重视节制欲望的缘故吧。
Conception and fetal formation originate from the essence (Jing) and blood of both men and women. Men belong to Yang, symbolizing the Qian trigram (representing Heaven and firmness), whose path initiates creation; women belong to Yin, symbolizing the Kun trigram (representing Earth and receptivity), whose path nurtures life. Yang is active, thus capable of bestowing; Yin is static, thus capable of receiving. Movement and stillness intermingle, Yin and Yang converge, and there must be a proper timing for conception to occur.
Typically, within one to three days after menstruation ends, the newly generated blood is not yet abundant, and the male essence surpasses the female menstrual blood. The essence opens up and envelops the blood; the essence enters to form the foundation of the skeleton, resulting in a male fetus. From the fourth to the ninth day, the new blood gradually grows, and the blood surpasses the essence. The blood opens up and envelops the essence; the blood resides at the root, resulting in a female fetus. During the sixth to seventh days, conception rarely occurs; if it does, it is mostly a female fetus. Those seeking offspring should entirely rely on intercourse within three days after menstruation ceases. This is as easy as picking up mustard seeds by bowing one's head, with every attempt being successful. At this time, neither man nor woman should experience violent anger, avoid drunkenness or overeating, refrain from consuming roasted, fried, or pungent-hot foods, and avoid using other methods to assist. By achieving Yin-Yang harmony and smooth flow of essence and blood, intercourse will inevitably lead to pregnancy, pregnancy will inevitably lead to healthy childbirth, and the child will be robust, strong, and long-lived. The most crucial points are contained in these few sentences.
After conception, one should maintain mental tranquility so that Qi and blood remain harmonious, allowing the fetus to grow and develop properly. Internally, one must stay away from excessive Seven Emotions (Joy, Anger, Worry, Thought, Sadness, Fear, Fright); externally, one must avoid strong flavors of the Five Flavors and foods that are excessively cold or hot, all of which are prohibited. If there are no symptoms such as abdominal pain during pregnancy, restless fetus, spotting, diarrhea, dysentery, or invasion by Wind-Cold external pathogens, medication should not be taken lightly. Intercourse must also be avoided to prevent stirring up desire. Before delivery, frequent intercourse leads to irregular fetal movement; after delivery, indulgence prevents the clearing of fetal toxins. After birth, nursing and care should be as meticulous as during the prenatal period. This is because if the mother consumes hot-natured food, her milk becomes hot; if she consumes cold-natured food, her milk becomes cold; if she consumes rich, greasy, or pungent foods, her milk becomes toxic. In such cases, the child suffers harm. The way to seek heirs indeed lies in these principles. However, the aspect of the "source" requires particular study.
Men have free-flowing essence at sixteen but should not marry until thirty; women receive Tian Gui (the substance promoting reproductive maturity) at fourteen but should not marry until twenty. This ensures that Yin and Yang Qi are complete and solid. If one engages in intercourse before essence is free-flowing, or approaches men when menstruation first begins, the body is damaged before maturity, and vitality is depleted before fullness. Since the root is already thin, the branches and leaves must wither; how can descendants flourish? Former Confucians stated that restraining desires leads to having children. This is likely because restraining desires prevents reckless intercourse, allowing Qi to accumulate and Essence to store, waiting for the right moment to act, thus enabling procreation. I believe this goes beyond mere physical restraint; any movement of the mind constitutes desire. The Heart governs Blood and houses the Shen (Spirit), belonging to the Hand Shaoyin meridian; the Kidney governs Essence and houses the Zhi (Will), belonging to the Foot Shaoyin meridian. If the Heart-Shen wanders outward, the Kidney-Zhi becomes chaotic inwardly. At the time of intercourse, there is no pure and tranquil Qi, and the discharged essence returns to corruption and turbidity. How can development and nourishment occur therein? The Book of Documents states: "The human mind is perilous; the Dao mind is subtle." If one focuses solely on the Dao mind, making it the master of the body, evil thoughts and delusions will naturally retreat. With fewer desires, Shen becomes more complete, leading not only to many children but also to longevity. This is because health preservation particularly values the restraint of desires.