Patient's question:
I got married last year. Recently, I've been experiencing lower abdominal pain, especially during my period. I'm very worried about it affecting fertility, and I'm also extremely sensitive to cold and coldness. How long does it take for an egg to be fertilized?Doctor's answer:
During sexual intercourse, a man releases approximately 200 to 400 million sperm each time. Most of the sperm are expelled from the vagina along with the semen, while a small portion advances through the uterine cervix and the uterine cavity by the movement of their tails, ultimately reaching the destination—the ampulla of the fallopian tube—where they wait to fertilize the egg. It takes only a few minutes for sperm to travel from the vagina to the fallopian tube, with the latest time being 4 to 6 hours, generally taking 1 to 1.5 hours. During their journey, sperm encounter resistance from cervical mucus and are phagocytosed by white blood cells in the uterine cavity, leaving only dozens to a couple of hundred sperm to reach the fallopian tube.Before fertilizing the egg, sperm must undergo a period of incubation in the female reproductive tract to gain the ability to fertilize, a process called capacitation.
Sperm can survive in the female fallopian tube for 1 to 3 days, while the egg survives for about 1 day. If sexual intercourse occurs within a few days before or after the woman's ovulation day, sperm and eggs may meet in the ampulla of the fallopian tube. At this point, a group of sperm surround the egg. Capacitated sperm secrete acrosomal enzymes from their heads to dissolve the corona radiata and the zona pellucida around the egg, creating a path for the sperm to enter. Ultimately, only one sperm enters the egg, forming a new cell called a zygote or blastocyst. This process is known as fertilization.
The zygote absorbs nutrients and oxygen from the fluid secreted by the fallopian tube and undergoes continuous cell division. Meanwhile, the zygote gradually moves toward the uterine cavity and, by 3 to 4 days later, has developed into a multicellular solid structure resembling a mulberry, hence called a morula. The morula continues to divide into a blastocyst within the uterine cavity. Around 6 to 8 days after fertilization, the blastocyst enters the endometrium, a process called implantation or embedding.
After implantation, the blastocyst gradually develops within the uterine cavity. By 5 to 8 weeks post-fertilization, it has developed into an embryo, and after 9 weeks, it becomes a fetus.