Human Reproductive Cycles and Fertility Management

Reproductive Cycles

For a successful reproduction, the ovarian and uterine cycles must be synchronized.

The Ovarian Cycle

The ovarian cycle consists of the maturation of an ovule every 28 days. Its phases include:

• Follicular: Days 1-14; follicle development occurs, and only one will mature.
• Ovulation: Day 14; the release of the matured egg into the fallopian tube.
• Luteal: Days 15-28; the empty follicle produces progesterone.

The Uterine Cycle

The uterine cycle prepares the uterus for the implantation of a fertilized egg. Its phases include:

• Menstrual: Days 1-5; bleeding occurs that eliminates the endometrium.
• Proliferative: Days 5-14; the endometrium regenerates and the cervix opens up. The uterus produces an egg-white type of discharge.
• Secretory: Days 14-28; the endometrium degenerates.

Stages of Embryonic Development

For embryonic development to occur, the union of an egg and sperm is necessary. Each contributes 23 chromosomes, including sex chromosomes. The stages are:

• Ovum: Before fertilization.
• Zygote: The first cell.
• Blastocyst: The germinal stage, consisting of a cluster of cells.
• Embryo: The period of embryonic development.
• Fetus: The fetal stage.

The Three Stages of Labour

Dilatation

During dilatation, uterine contractions pull the cervix and modify its shape and diameter. Its phases are:

• Latent: The cervix opens to 6 cm; contractions are mild and irregular. This may last hours or days.
• Active Labour: The cervix opens from 6-10 cm; contractions become stronger, longer, and more frequent.
• Transition: The final, intense part of active labour when the cervix reaches 10 cm.

Pushing and Birth

Pushing begins when the cervix is fully dilated and ends with the birth of the baby. Its stages include:

• Pushing: Contractions push the baby down the birth canal.
• Birth: The baby's head becomes visible; in 2-3 pushes, the baby is out.

Afterbirth

Following the birth of the baby, the uterus contracts to expel the placenta.

Contraceptive Methods

Natural and Barrier Methods

• Natural methods: These include Abstinence, Ogino (counting days to avoid sex during fertile periods), Basal (checking daily vaginal temperature to identify ovulation), and Withdrawal (penis withdrawn before ejaculating).
• Barrier methods: These prevent sperm from reaching the egg and include condoms and the diaphragm (which must be combined with spermicides).

Chemical, Hormonal, and Surgical Methods

• Chemicals/Hormonal: Spermicides (alter sperm motility and survival), the pill (alters ovulation or menstruation), implants (annual, releases hormones under the skin), injections (hormones that inhibit ovulation), the vaginal ring (inserted in the vagina; 3 weeks on, 1 week off), and the patch (hormones through the skin; 3 weeks on, 1 week off).
• Preventing Implantation: The IUD (triple function: prevents development of the endometrium, metal acts as a spermicide, and can be impregnated with hormones) and the morning-after pill (a hormonal cocktail that induces the shedding of the endometrium; should be taken within 72 hours of unprotected sex; not a regular method, just for emergencies).
• Surgical: Vasectomy (cutting or tying the vas deferens) and tubal ligation (sectioning of the fallopian tubes).

Assisted Reproduction Techniques

These techniques allow people with fertility problems, same-sex couples, or single-parent families to have offspring.

• Artificial Insemination: Sperm is introduced into the female genital tract so that fertilization occurs naturally.
• In Vitro Fertilization (IVF): An egg is fertilized by sperm in a lab, and the embryo is then transferred to the uterus. Gametes can come from donors.
• Sperm Microinjection: The sperm is injected directly into the egg to ensure fertilization.
• Preimplantation Genetic Diagnosis: Genetically analyzing the embryo before it is implanted in the uterus.
• Surrogacy: Pregnancy takes place in the uterus of a woman who is not part of the couple.
• Cryopreservation: Sperm, eggs, and embryos are kept frozen for later use.