Planting and nurturing seedlings require basic conditions such as seeds, soil, nutrients, and are affected by various factors during the growth process like climate and pests. Similarly, conceiving a baby involves various factors that can be summarized as follows:

Healthy “Seeds”

The production of healthy sperm by the father and healthy eggs by the mother, which can successfully combine and develop.
The conditions for producing healthy sperm include overall physical health, absence of major diseases or chromosomal abnormalities, and normal results from pre-conception examinations.
Producing healthy eggs is also not straightforward. Factors like age, genetics, ovarian reserve, hormones, immunity, living environment, and habits can affect female ovulation function and egg quality, sometimes leading to ovulation disorders, immature eggs, or abnormal fertilization.
Successful combination and development of sperm and egg refer to both partners having unobstructed reproductive tracts and engaging in regular sexual activity for the healthy egg to have a chance of fertilization in the ampulla of the fallopian tube (typically occurring 12-24 hours after ovulation). Subsequently, the fertilized egg is moved by the contractions of the fallopian tube and cilia within its cavity to reach the uterine cavity.

Fertile “Soil”

Normal uterine morphology, healthy endometrium, and synchronous development with the embryo.
Conditions like uterine fibroids, adenomyosis, or uterine malformations can adversely affect embryo implantation and development, although not all uterine abnormalities impact fertility. Diagnosis and tailored advice are provided by doctors based on specific circumstances.
The thickness of a healthy endometrium varies cyclically. At the end of menstruation, the endometrial thickness is ≤5mm, increasing to around 9mm when follicles mature. Besides adequate thickness, successful embryo implantation also requires a normal endometrial structure. Conditions like endometrial polyps or complex endometrial hyperplasia are not favorable for embryo implantation.
The endometrium has a brief period for accepting embryos known as the “implantation window.” This period starts around 5 days after ovulation and lasts for approximately 5 days. If during this time the embryo and endometrium do not synchronize in their development, successful embryo implantation becomes challenging.

Adequate “Nutrients”

Normal hormonal levels.
If the endometrium is the “soil,” estrogen and progesterone act as water and fertilizer. Additionally, several hormones work together to support embryo development, with their required balance varying across different stages of development. Experienced doctors provide specialized guidance to patients undergoing assisted reproduction.
Suitable “Environment”
Normal maternal immune environment, absence of “pests” (infections), and good mental and physical health.
The immune environment is intricate; abnormalities can lead to maternal and embryo “incompatibility,” hindering normal embryo development and potentially harming maternal health.
Absence of “pests” refers to infectious agents. Many pathogens can affect embryo development, necessitating the elimination of viruses, harmful bacteria, fungi, etc.
Good mental health refers to avoiding anxiety, depression, and other negative emotions that can affect the endocrine system, impeding embryo implantation and development.