Ageing and Fertility

As a woman’s age increases her ability to conceive decreases. This gradual decrease in fertility starts in the late 20’s and continues at a slow rate until age 35-37 and then becomes more pronounced as age approaches 40 and by 50 for most women there is only a very small chance of natural conception.

The ticking of the biological clock is not as inexorable as it seems. Both conventional and natural medicine can help women improve their chances of conception even late into their reproductive life. Natural (non-pharmaceutical drug) assisted reproductive medicine can improve a woman’s chances of becoming pregnant.  The reasons for the decreased fertility rate with age are multi-fold. Many women, married or unmarried, are waiting longer before attempting pregnancy.

As sexually active women grow older, the likelihood that they might be exposed to sexually transmitted infections increases. These infections (such as chlamydia) are in many cases asymptomatic and can permanently damage the pelvic organs which can further reduce a woman’s ability to become pregnant.

The chance that a woman might experience fertility related complications from endometriosis or adenomyosis (disorders which involve uterine lining cells- endometrial cells implanting in abnormal locations in the pelvis) also increase with age. 

One of the most important explanations for age-related infertility in women is the declining number of genetically normal available eggs. The peak number of eggs (oocytes) is achieved before her birth and long before a women even consider becoming pregnant. The fetus at 4-5 months gestation possesses 6-7 million eggs. By birth, this number drops to around 1-2 million and declines even further when, at the start of puberty in normal girls, there are 300,000-500,000 eggs.

Several hundred oocytes are lost during the 3rd-4th decades if a woman has regular menstrual cycles. Many further oocytes are lost through natural cell death. When a woman reaches her mid to late 30s, when she has about 25,000 eggs left in her ovaries and the loss rate of oocytes accelerates as she gets older. In addition, as a woman ages the ability of her oocytes to divide and distribute the genetic contents normally declines. The likelihood that an oocyte with an abnormal number of chromosomes will be fertilized increases with age.

Older women have a gradually increasing risk of pregnancies which are genetically abnormal. Most of these genetically abnormal pregnancies are miscarried in the first trimester of pregnancy. Unfortunately, older women (past the age of 40) also have a higher risk of miscarrying even genetically normal pregnancies with the rate increasing from 1 in 5-6 on average below age 35 to 1 in 3-4 on average over the age 35. 

Average time to conceive for healthy women under the age of 35 with unprotected intercourse twice a week

After age 35, however, all the above numbers can be divided in half. As far as having sex when ovulating the timing of sexual intercourse should be optimised. Even then it is not possible to know for sure the right time has been hit unless basal body temperatures (BBT) and cervical mucus changes are charted.

In general, if menses are regular (28 days from start of one to start of another), having sexual intercourse from day 11 to day 17 from the start of the last menses every other day if possible is the best way to assure timing to coincide with ovulation and the male partners highest quality sperm is inside the fallopian tubes when ovulation occurs. If menses are regular but longer than 28 days, for each day longer than 28 days, add that number of days to the 11-17. For example, at a regular 30-day cycle, time intercourse for days 13-19 after the start of a previous period. 

There are two levels of Natural Assisted Reproductive Medicine. The first level uses “natural fertility herbal medicines” which can enhance an older woman’s ability to conceive. Using these natural medications can increase not only the number of available oocytes which mature and are then available for fertilisation, but also the quality of the maturing oocytes. When this treatment combined with basal body temperature charting (BBT) and hormone level tests to determine optimum time in the cycle for conception can dramatically increase an older woman’s chances of conception.

The second level is using natural vitro fertilisation (known as Natural IVF). Here a woman matures her oocyte naturally and just before ovulation the single mature oocyte is extracted using a minimally invasive procedure. In the lab, the extracted oocyte is mixed with her partners (or donated) sperm and returned to her uterus several days later once the fertilised oocyte has begun dividing.  Unfortunately, not all 40-year-old (or even 30-year-old) women respond to fertility treatments in the same way.

By measuring two hormone levels—oestrogen, follicular stimulating hormone (FSH) and Anti-Mullerian Hormone (AMH) on the first to third day of a woman’s menstrual cycle, an accurate assessment of the likelihood that a woman may respond to fertility herbal medicine can be made.

Elevated FSH and reduced AMH levels usually indicate a decline in normal, available oocytes. A woman with abnormal day 1 hormone levels possesses a much lower likelihood of responding well to fertility treatments as well as a lower chance of becoming pregnant when compared to a woman of the same age with normal oestrogen, FSH and AMH levels.

The one caveat is that all these explanations of ageing and fertility are not absolute. There are many cases of women in their 40s having failed multiple stimulated IVF cycles that then become pregnant with natural fertility medication. 

Turning 40 does not mean women can no longer bear children, only that she might need assistance along the way to conceive and then assistance to carry to term.