Episode 352: How Do Female Fertility, Infertility and PCOS Treatment, and IVF Work?

TL;DR

Female fertility relies on a finite egg supply, hormone-regulated ovulation, fertilization in a fallopian tube, and successful implantation in the uterus. About two million eggs remain at birth, falling to roughly 400,000 by menstruation, while IVF typically fertilizes about 70% of collected eggs. Read on to understand ovarian aging, chromosome errors, fertility evaluation, and pregnancy precautions.

Transcript

Getting this looked at now is a great way to get ahead of an infertility problem 10 years hence. For sure. Women are born with a finite number of eggs. Actually, the most eggs you'll ever have is when you're in your mom's womb. So, let's just walk through how IVF works. Usually about 70% of the eggs fertilized. That's an important message for anybo... Read More

Key Insights

• Women have a finite egg reserve established before birth. The greatest number exists during fetal development, about two million remain at birth, and roughly 400,000 remain when menstruation begins, with most ovarian eggs disappearing through a process called atresia.
• Ovulation is regulated primarily by follicle-stimulating hormone and luteinizing hormone. These pituitary hormones stimulate a group of ovarian follicles to grow, after which one follicle usually becomes dominant and releases its egg, although the precise basis of that selection remains partly unknown.
• Fertilization normally occurs inside a fallopian tube. After sperm fertilizes an egg, the resulting zygote or embryo travels toward the uterus, where it may implant in the uterine lining and establish a pregnancy.
• Egg cells remain arrested during meiosis until development around ovulation and fertilization continues the process. Chromosome pairs must separate evenly so the egg contributes one copy of each chromosome, and errors can leave the resulting embryo with an extra or missing chromosome.
• Maternal age is associated with declining egg quality and a greater probability of chromosome-division errors. A woman may continue ovulating regularly while releasing eggs that are less likely to fertilize normally, implant, or support continued development.
• Most embryos are described as chromosomally abnormal because most eggs are chromosomally abnormal. Biological selection occurs because chromosomally normal embryos are generally the ones that implant and continue developing, while chromosome abnormalities cause most miscarriages discussed in the episode.
• Menstrual patterns are markers of reproductive health and may reveal important problems before pregnancy is attempted. Investigating irregularities early can help identify a potential infertility issue years before someone is ready to conceive.
• GLP-1 agonists should not be used while trying to become pregnant. The recommendation stated in the discussion is to stop treatment for at least two months before pregnancy attempts, although these medicines may be used before that pre-pregnancy period.

Questions & Answers

Q: How do female fertility and IVF work?

Women are born with a finite egg supply, and FSH and LH stimulate follicles until one usually becomes dominant and releases an egg. Fertilization normally occurs in a fallopian tube, after which the embryo travels to the uterus and may implant. In the IVF discussion, about 70% of the eggs are usually fertilized.

Q: How does the female egg reserve change over time?

The largest egg supply exists during fetal development. About two million eggs remain at birth, falling to roughly 400,000 by the start of menstruation around ages 12 to 14. Most ovarian eggs disappear through atresia rather than ovulation.

Q: How do FSH and LH control follicle growth and ovulation?

Follicle-stimulating hormone and luteinizing hormone are pituitary hormones that drive follicle growth. A group of follicles starts developing, their surrounding cells divide, and one follicle usually becomes dominant and releases its egg. The precise selection process remains partly unknown.

Q: Where do fertilization and implantation occur?

After ovulation, the egg normally enters a fallopian tube connecting the ovary and uterus. Fertilization usually occurs in that tube when sperm is present. The resulting zygote or embryo travels into the uterus, where it may implant in the uterine lining.

Q: Why does female fertility decline with age?

Egg quality declines as women grow older, even when regular ovulation continues. During meiosis, chromosome pairs must separate evenly, but errors can leave an egg with an extra or missing chromosome. These errors become more likely with maternal age and can reduce the chances of normal fertilization, implantation, or continued development.

Q: How can chromosome abnormalities cause miscarriage?

The egg and sperm must each contribute a single chromosome set. Uneven chromosome separation in the egg can produce an embryo with an abnormal chromosome number, disrupting development. The episode identifies chromosome abnormalities as the cause of most miscarriages discussed.

Q: When should possible fertility problems be investigated?

Potential reproductive problems should be investigated before someone is ready to attempt pregnancy, especially when menstrual patterns suggest an issue. Periods can act as markers of reproductive health. Early assessment may reveal a possible infertility problem as much as 10 years before planned conception.

Q: When should GLP-1 agonists be stopped before pregnancy?

Someone trying to become pregnant should not remain on a GLP-1 agonist. The recommendation in the discussion is to stop the medication for at least two months before attempting pregnancy. It may be used before that pre-pregnancy period, including in discussions of PCOS treatment.

Summary & Key Takeaways

• Women have their largest egg supply while developing in the womb, with about two million eggs remaining at birth and roughly 400,000 by the start of menstruation. During a typical cycle, FSH and LH stimulate several follicles, one usually becomes dominant, and its egg is released into a fallopian tube.

• Fertilization normally occurs in a fallopian tube, after which the developing embryo travels toward the uterus and may implant in its lining. Chromosome separation errors during egg maturation can create embryos with abnormal chromosome numbers. These abnormalities become more likely with maternal age and account for most miscarriages discussed in the episode.

• Fertility assessment should not be postponed until pregnancy attempts begin because menstrual patterns can serve as markers of reproductive health. Both partners should be evaluated early when infertility is suspected. Available approaches include PCOS treatment, IVF, preimplantation genetic testing, and egg freezing, while lifestyle factors and medication use also require consideration.