生育治療

The chance of getting pregnant decreases with increasing age. This is true for both partners, but more so for the woman than the man.  Humans are not very fertile animals.  Even for the most fertile young couples, the chance of getting pregnant is only about 20% each month.  This is because a woman produces one mature egg per month (if there is regular ovulation) and this egg survives 24 hours only.  This is the bottleneck of human fertility.  As a woman ages, the quality of the ovulated egg may also diminish, making it even harder to get pregnant.  Generally speaking, 60-70% of couples are pregnant after 6 months of trying and 80% – 90% of couples are pregnant after 12 months of trying.

WHO (World Health Organisation) definition of infertility is “failure to conceive after 12 months of unprotected intercourse”.  Generally, it is recommend couples seek medical advice if they have not conceived after 12 months of unprotected intercourse, provided the female partner’s age is less than 35.  If she is 35 or older, it is actually recommend the couple seek medical attention after 6 months of trying.  The older one gets, the longer it takes to get pregnant, the longer one waits, the older one gets – a classic “Catch -22” situation.

With news of 60+ year olds having babies, it seems as if there is really no limit to the age of having a child.  The implication of this question is as follows:

1. What is the oldest age a woman can get pregnant?
2. What are the difficulties older women encounter in pregnancy?
3. Are the babies going to be normal?

There is no definitive rule as to the oldest age for a woman to get pregnant.  Generally speaking, fertility declines after 35 and falls sharply after 40.  From personal experience, the oldest pregnant women Dr. Wang has cared for are 46 years old.  Importantly, they have all had children in the past conceived naturally (not by IVF) and the pregnancies they had at 46 were all natural pregnancies.  Of interest, all of them had perfectly healthy babies.

For Dr. Wang’s infertility patients, the oldest women getting pregnant with their own eggs were 46 but unfortunately they ended up miscarrying.  So far, in Dr. Wang’s experience, the oldest IVF patients succeeding having babies were 44 (when they got pregnant with their own eggs).

The medical difficulties women over 40 would face are multiple.  As indicated, the fertility of a woman ≥ 40 is drastically reduced.  Even after she gets pregnant, the miscarriage rate is significantly higher.  For example, a 40 year old has almost 50% chance of a miscarriage compared with 15-20% for the general population.

The chances of medical complications are also increased: the common ones are “pregnancy induced hypertension” and “pregnancy related diabetes”.  It is generally felt that “older” women do not labour (poor contractions or “posterior” positions are examples) as well as younger women.  As a result of these reasons, they are more likely to undergo C-sections.

The chance of a baby having a chromosomal abnormality (a major genetic problem) is about 1/100 for a 40 year-old woman and about 1/250-300 for a 35 year-old woman.  Although the chance of genetic disorder is higher, 1/100 means that most babies are perfectly healthy.  There are antenatal tests that can be undertaken to assess these risks and abnormalities.

It is beyond the scope of this space to discuss the social and psychological adaptation of having children late in life (or at any time in life, for that matter).

The egg count test is a test for anti-Müllerian hormone (AMH).  This is a simple blood test that can be done at any time of the menstrual cycle.  AMH is produced by the primitive little eggs of the ovaries.  Once the primitive eggs start growing, they effectively stop producing AMH. As a result, the AMH is a good test measuring the number of primitive eggs a woman have.

A woman is born with all the eggs she will ever have in her life. These eggs are gradually used up over the years. At birth and in pre-pubertal years, these eggs are all held in the ovaries as primitive little eggs.  When ovulation occurs after puberty, one’s body will select a crop of these little eggs at the beginning of each menstrual cycle. These primitive eggs will start growing and out of this crop, only one will ovulate and the other eggs will grow to “half way” and “die off”.  The primitive eggs represent the woman’s potential for future ovulation and as ovulation is crucial for getting pregnant, the primitive eggs are indicative of one’s fertility potential.

What needs to be clarified is that AMH is a reflection of egg number and not egg QUALITY. Good egg quality is far more important to getting pregnant than egg numbers. Unfortunately, there is no simple test for egg quality to date. AMH is as close as we have to a measure of ovarian reserve.

IVF does not lead to premature menopause. The multiple eggs produced as a result of an IVF cycle are eggs the woman would have wasted normally in a natural cycle.  As such, IVF salvages more eggs that a woman would not normally have.  All women are born with a finite number of eggs. They are held in the ovaries in a primitive state.  In a natural cycle, the woman’s body selects a crop of 10 to 30 primitive eggs to start the ovulation process. These eggs start growing under hormonal influence, but ultimately, only one egg reaches the mature stage and is ovulated. All the other 10 to 30 eggs get to “half way” and “die off” so that in a natural cycle, only one egg is ovulated.  In an IVF cycle, the control is temporarily taken over by the IVF drugs so that we “salvage” as many of the “half way” eggs as possible and get them to the mature stage.  This is why the IVF process “salvages” more eggs and does not “use up” what the woman would normally have.