Understanding Human Reproduction and Infertility

Fertilization

Fertilization occurs when a sperm and an ovum unite, forming a zygote. This process requires both ovulation and sexual intercourse. It's only possible during a 24-48 hour window after ovulation, although sperm can survive up to 5 days inside the female reproductive tract. The sperm penetrates the ovum's covering, and a fertilizing membrane forms, preventing other sperm from entering. The nuclei of the sperm and ovum join. After fertilization, the zygote travels to the uterus. The corpus luteum continues to release progesterone, maintaining the thick endometrium walls and preventing menstruation. During its journey, the zygote divides, becoming a ball of cells called a morula (around day 4) and then a blastocyst (around day 5). The blastocyst implants in the endometrium approximately 7 days after fertilization.

Stages of Pregnancy

• Pregnancy: Begins with the implantation of the blastocyst in the endometrium. The blastocyst develops into an embryo with essential structures.
• Placenta: An organ with many blood vessels that allows nutrients to pass from the mother's blood to the fetus. Waste products from the fetus are also released into the mother's blood.
• Umbilical cord: Connects the embryo/fetus to the placenta.
• Amniotic sac: Contains amniotic fluid, which protects the embryo/fetus.

Childbirth

Childbirth is the process that enables the baby to be born at the end of the pregnancy. The uterus contracts rhythmically and powerfully, expelling the fetus from the mother.

• Dilation: Involuntary contractions of the uterus begin. The cervix shortens and increases in diameter. The amniotic sac ruptures ('breaking waters'), and the fetus moves towards the birth canal.
• Birth: Contractions become more intense and frequent. The baby is born, and the umbilical cord is cut.
• Afterbirth: The placenta is expelled. Colostrum and milk production begin.

Infertility

Infertility is the inability to conceive children naturally.

Female Infertility

• Lack of ovulation: Due to hormonal factors or ovarian abnormalities.
• Uterus problems: Prevents implantation.
• Fallopian tube obstruction: Prevents the egg from reaching the uterus.

Male Infertility

• Low sperm count.
• Immature or malformed sperm.
• Sperm and vaginal mucus incompatibility.
• Vas deferens obstruction.

Assisted Reproduction Techniques

• Artificial insemination (AI): Semen is artificially inserted into the woman's uterus. This can bypass obstructions in either the man or the woman.
• In vitro fertilization (IVF):
  1. Ova are extracted.
  2. The man's sperm is collected.
  3. Fertilization takes place in a laboratory.
  4. Developed embryos are transferred to the uterus. Multiple pregnancies may result if several embryos develop.

Birth Control Methods

Birth control methods are used to prevent pregnancy.

• Natural methods: Based on physiological changes in the woman's sexual cycle. Examples include symptom-based methods, calendar-based methods, and *coitus interruptus*.
• Artificial methods: These can be barrier, chemical, or surgical methods.
• Barrier methods: Male condom, female condom, diaphragm, intrauterine device (IUD).
• Chemical methods: Contraceptive pills, patches, vaginal rings, hormonal IUDs, and spermicides.
• Surgical methods: Tubal ligation (for women) and vasectomy (for men).