Biology, Fundamentals

The Biological Clock Ticks Faster than Most Think

biological clock

“Though it seems hard to believe, the biological clock begins ticking before female babies are even born.”  Dr. Marie Savard

In researching this subject, I found that some young women today are still unaware that you cannot have a baby too late in life. But there is an unalterable number of oocytes (eggs) with which a woman is born. Techniques to aid in in conception, such as in-vitro fertilization (IVF) and hormone treatments, cannot change the fact that her eggs are depleted and are of a lower quality later in life. Many factors are involved in fertility as a woman ages.

Facts on the Female Biological Clock

A twenty week old fetus has about seven million eggs, but at birth there are only one to two million left.  By age 30, 90% of eggs have been lost, and the clock begins to tick. At 40 years old, only about 3% remain. Only about 450 of the eggs she was born with will mature.

Common Misconceptions

“I plan to be super fit, super in shape when I’m 40, 50,”

says Lisa Bourne.

“And if I’m physically able to do it, then I will have a child at 55.”

Women delay pregnancy during their highest fertility ages for various reasons, such as career focus, lack of financial stability or they haven’t found Mr. Right. Dr. Pasquale Patrizio, professor in the Department of Obstetrics & Gynecology at Yale School of Medicine and director of the Yale Fertility Center, noticed that women ages 43 or older were coming to his fertility clinic and expecting to easily become pregnant, only to be disappointed. They believed that being healthy and exercising was the big factor in fertility, but it isn’t.

Although IVF procedures for women 41 and older saw a 41% increase during 2003-2009, the pregnancy success rate stayed at the usual 9%. Successful pregnancies still face complications, such as miscarriage and birth defects. By age 37, fertility drops drastically. By age 44, pregnancy with her own eggs is virtually impossible.

Skirting the Biological Clock

There are ways to skirt the ticking of the biological clock, such as oocyte (egg) freezing. The egg contains a large amount of water. Ice crystals will form within the egg, which destroys the DNA. The egg is dehydrated before freezing to prevent this from happening. Cryoprotectants replace the water inside the cell. DNA damage can also occur during thawing. Vitrification is a method that uses a “super-fast cooling” technique, and over 2,000 healthy babies have been born as of 2012. Results are best for women 35 or younger. The cost is pretty high at $10,000 a pop and $500 per year for storage.

Embryo Freezing is another option to outsmart the biological clock. An embryo, a fertilized egg, is frozen for later implantation into the uterus. The younger the parent’s sperm and egg, the more likely it is that they will have a healthy baby later on. Approximately 25% of babies born using IVF procedures are from frozen embryos.  An advantage of freezing embryos instead of eggs is that presently the eggs cannot be tested for defects, while an embryo can.

The ovaries hold the ticking clock, not the uterus. Ovarian tissue cryopreservation is an option. It possible to extract strips of an ovary, or the entire ovary, and freeze it. It can be transplanted into the uterus when the woman is ready. More on this, here on WebMD.

Assessing Reproductive Age

There are hormones that are responsible for egg maturation and conception. These can approximate when the clock will run out. Anti-Mullerian hormone can estimate the remaining egg supply. It peaks at age 24, is half that at mid-30s and practically gone by 40. IVF is less successful when the anti-Mullerian hormone levels fall too low.

Follicle Stimulating Hormone (FSH) is a standard test of how fast the biological clock is ticking, but it is not definitive in its fertility assessment. This is because the eggs may not be quality. FSH is less predictive in younger women. |

New techniques are being developed now that may be able to make primitive cells, called primordial germ cells, which become sperm and egg, from skin cells.

As  shown, the biological clock still tick-tocks, but there are now ways to measure the time left, and sometimes to get around the clock altogether. It seems the message is the earlier the better when it comes to fertility and having a baby. New technology cannot beat the biological clock, but it sure can get around some of the more difficult problems. Nothing is fool proof.

biological clock
Figure of Mother Holding Child, Date 3rd–5th century, Geography Peru, Culture Moche
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