What is sitting in the womb to tell fortune?

After fertilization, the egg is sent to the uterine cavity through the peristalsis of the fallopian tube. It takes about 3 ~ 4 days from fertilization to delivery to uterus, and the fertilized egg will be free in the uterine cavity for 2 ~ 3 days. In this process, the fertilized egg continuously divides and proliferates, and gradually forms a cell mass called embryo sac or blastocyst. About 7 ~ 8 days after fertilization, the blastocyst has reached a suitable position in the uterine cavity and "rooted" in the endometrium (medically called "implantation"). This process is called pregnancy and implantation, which is also commonly known as "sitting on the fetus".

After blastocyst implantation, the endometrium changes with the changes of hormones in the body after conception. The endometrium no longer exfoliates to form menstruation, but becomes decidua, which wraps the blastocyst and provides nutrition for it to further develop and grow. Later, with the development of blastocyst and the growth of fetus, fetus and its appendages gradually occupied the whole uterine cavity.