Causes for Subfertility


Causes for Subfertility

As a gynaecologist with a special interest in the field of Fertility, the commonest question I encountered during my daily clinical practice is:  when does a couple needs to come in for a fertility assessment?  Many times we encountered couples who knock on our doors 3 months after trying to have a baby. Many of them would appear to be in distress thinking that there is a major problem with their fertility. Conversely, I have also encountered couples who remained childless for more than 10-15 years, only appearing on my doorstep at the age of 45 or more, hoping that the modern Fertility Treatment would overcome the odds and help them to achieve a pregnancy. For this specific group of patients, the majority would say that they were not aware of the tests which can be done and were not aware of the multiple Fertility Treatments available.

So where do we draw the line and achieve a balance between starting to investigate too early and too late?  What is the common practice and what is the basis to it?

(1)    What is the definition of Subfertility?


Pregnancy occurs when the egg meets the sperm and gets fertilized to form an embryo at the fallopian tube. The embryo then travels down through the fallopian tube to get implanted at the lining of the womb (endometrium). Although this is a simplified version of explaining how pregnancy occurs, the actual process is a result of a complex combination of factors.  Therefore, even when everything works perfectly, conception can take time.


A healthy woman under the age of 30 has about a 20% chance to get pregnant each time she ovulates. About 80% of couples can expect to conceive during the first year of trying to become pregnant. However, after twelve months of trying, the chance of getting pregnant decreases with time. By the second year of trying, the chance of getting pregnant naturally drops down to 1-2% per cycle.


It is also important to note that fertility declines with age. After the age of 35, women experience numerous physiological changes which contribute to a significant decline in fertility.  This is partly due to a declining ovarian reserve, the quality of their eggs and changes in their hormones. By the age of 40, there is a further sharp decline in fertility rate.


Subfertility is defined as the failure to achieve a successful pregnancy after twelve months of regular unprotected intercourse. However, if you are over 35 years of age and after trying for 6 months, you may want to start looking into checking your fertility.


(2)    When should I see a doctor to get my fertility checked?

In a young couple, it is reasonable to seek medical evaluation and advice after twelve months of trying. However, if the female partner is over the age of 35, medical evaluation may be warranted after six months.


(3)    How common is the problem of subfertility in the general population?

One in every six couples have problem in conceiving but most can be overcome by simple measures such as changing their lifestyle, improve on their nutrition and health, timing the intercourse during the fertile period.


(4)    What are the common causes of subfertility for a woman?

(a)   Ovulation problems

Most women (95%) under the age of 35 who have regular menstrual cycles ovulate regularly. Some women who experience problems with hormonal imbalances may have problem with ovulations.


If the body is not producing enough of a particular hormone or fails to release a particular hormone at the right time, ovulation does not happen. This is more apparent in women who have significant changes in weight in a short span of time, eg. In anorexic patients


In some women with an inherited condition called Polycystic Ovary Syndrome, whereby there is an association with high levels of insulin and male hormones, ovulation does not occur regularly. This condition may be worsened when the woman puts on weight.


(b)   Fallopian tube problems

Fertilization occurs at the Fallopian tube and the embryos travel down and get implanted into the lining of the womb. If the Fallopian tubes are damaged or blocked, sperm could not meet the eggs and therefore fertilization does not occur.


Fallopian tubes may be damaged due to:

  • Infections particularly chlamydia infections can cause tubal damage
  • Previous ectopic pregnancy
  • Endometriosis, a condition associated with the growth of the cells originates from the lining of the womb (endometrium) which get deposited outside the womb
  • Previous abdominal or pelvic surgery which causes scarring around the Fallopian tubes
  • Pelvic inflammatory diseases


(c)    Problems associated with the womb (uterus)

Fibroid or Myoma, a benign growth in the uterus, can sometimes distort the lining of the womb and causes problem with implantation and therefore causes subfertility.  Scarring of the lining of the womb, which may be caused by previous surgery such as Dilatation and Curettage (D & C), infections or inflammation can potentially prevents implantation of the embryos. In rare cases whereby there is a congenital abnormality in the shape of the uterus, implantation may be difficult and sometimes there is a higher chance of miscarriage or pre-term delivery.


(d)   Problems associated with the immune system

In rare circumstance, some women develop antibodies which attack the embryos and inhibit implantation and causing miscarriages. This can be one of the causes of subfertility


(5)    What are the common causes of subfertility for men?

Up to 40-50% of causes of subfertility are associated with male issues.  Poor sperm quantity (oligospermia) and quality (poor motility or asthenozoospermia, poor morphology or teratospermia) is associated with subfertility and can be identified by performing a semen analysis. This test would also guide the doctor in making decision on which fertility treatment would be appropriate for the couples.


(6)    What is the meaning of unexplained subfertility?


In general, up to 25% of couples will not find any causes for their subfertility after going through fertility testing. This group of patients is categorized as unexplained fertility. This diagnosis can be frustrating as many of them would wonder: why is it that they have not achieved a pregnancy given that all the test results had been normal?


The important thing to note is that even though all the tests had been normal, but it does not mean that there are no factors that prohibit them from having a baby naturally. It is important to note that they have only had essential and simple fertility tests. These tests do not always assess function. For example, despite showing tubal patency through a dye test or a diagnostic laparoscopy, it does not ensure normal transport of eggs and sperm in tubes as there has not been a valid test for this.

Dr Helena Lim Yun Hsuen

KL Fertility & Gynaecology Centre

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