Where do babies come from?
The easiest way to understand why a couple is having trouble getting pregnant is to first understand how pregnancy happens normally. There are series of steps that have to happen in order to have a successful pregnancy:
- The male partner will produce sperm in his testis, which will be stored in a structure near the testes called the epididymis and then travel through the vas deferens, a long tube that runs through the penis and be released during ejaculation.
- In the female partner, a few of the eggs inside fluid filled structures called follicles, begin growing at the time of the menstrual cycle, but only of these will become dominant and release at the middle of the cycle (around day 14).
- Following ovulation, the egg will be picked up by the fimbria, finger like projections on the end of the fallopian tube and begin its journey towards the uterus.
- The couple will have intercourse and millions of swimming sperm will be deposited in the vagina.
- Some of these sperm will make it to the cervix (the neck of the uterus) which at midcycle produces thin watery mucus secretions that help the sperm survive for up to 3 days.
- The hardiest of these sperm will exit the cervix and swim up the through the uterus and eventually make it to the distal (far) end of the fallopian tube.
- A single sperm will enter into the egg in a process called fertilization.
- Over the next week, the fertilized egg will continue to divide and eventually reach a stage of development called the blastocyst, as it makes its way downstream into the uterus (womb)
- The blastocyst will implant itself into the lining of the womb, commonly known as the endometrium.
- What is left of the follicle has turned into a structure called the corpus luteum, a little hormone factory which will produce progesterone and other hormones to help prepare the uterus for implantation and prevent the next period from starting.
- If the pregnancy implants, it will begin to secrete a hormone called hCG (human chorionic gonadotropin), which is the chemical we look for in a pregnancy test. The early pregnancy will eventually secrete enough hCG to show up as a positive home pregnancy test around the same time as the next period is due.
- If the pregnancy fails to implant, the corpus luteum will wither away, its hormone production will drop, the lining of the uterus lose its support and the next menses will start.