PCOS is a hormonal imbalance which affects the fertility of women. Obesity is a well documented condition which results from increasing gain in weight. The relationship between the three variables of obesity, PCOS and pregnancy is quite complicated and still not fully understood. In short, it can be said that obesity contributes towards PCOS which in turn leads to difficult pregnancies or in a number of pregnancy complications and stillbirths. On the other hand, even if you have PCOS and are obese, you can conceive naturally with even a slight loss of weight. Hence, no clear cause and effect relationship has yet been scientifically established and this area continues to attract active research.

In order to understand the intricate relationship between polycystic ovarian syndrome, obesity and pregnancy, it is necessary to define and understand each of these terms.

What is obesity?

Obesity is a condition where you have excess body weight. It is identified in terms of a very well established clinical measure called BMI or body mass index. It measures your weight for a unit of surface area and is expressed as a ratio between your weight and height. If BMI exceeds 30, you are said to be obese. There are different degrees of obesity according to the BMI value.

What is PCOS?

PCOS or polycystic ovarian syndrome refers to a common hormonal disorder which affects about 7% of the women of reproductive age (12 to 45) in America. It is a condition when the body produces an excess of the male hormone called androgen. This disrupts the normal process of ovulation. The eggs are either not matured or not released and they appear as cysts in the sonogram – hence the name. The disorder leads to lack of menstruation. As ovulation is hindered, it affects your ability to conceive.

PCOS and pregnancy

Studies show that women with polycystic ovarian syndrome experience complications during pregnancy. These are as follows:

  • Since ovulation does not occur properly or the eggs are immature, you cannot identify your fertility period or know anything about your fertility cycle. This, as well as infrequent ovulation hinders the process of conception.
  • Observations show that women who become pregnant even with PCOS are at greater risk of several complications related to pregnancy. They are more vulnerable to miscarriage. The incidence of gestational diabetes and its complications are much more. They also have to opt for C-section more frequently etc.

Relationship between PCOS and obesity

Well documented studies exist to show that the hormonal disorder of PCOS has a direct impact on the ovulation system in a woman's body. According to one study, at least 50% of the women who have PCOS are obese. Another study showed that in obese women with PCOS, 20% of the pregnancies ended in miscarriage while another 20% had congenital anomalies.

It is not clear how exactly obesity and PCOS are related. The reason is that the hormone imbalance which leads to polycystic ovarian syndrome and over secretion of androgen is not yet fully understood. However, most research suggests that obesity and PCOS is related through the hormone insulin and the resistance of your body to it.

One of the common factors of PCOS is the resistance to insulin. This is recorded even if you are not obese. Insulin has a recorded gonadotropic function in that it helps in stimulating the production of androgen. Studies suggest that obesity is at least partly responsible for insulin resistance in women with PCOS. It should be remembered that hyperinsulinemia may occur even in women within the normal weight range, but the condition is highly aggravated by obesity, especially the abdominal phenotype. This means the excess weight is concentrated in the lower body as happens in case of women. In case of obese men, the excess weight tends to concentrate on the upper body.

In normal condition, the production of insulin and the sensitivity of the body to it are finely balanced. If the insulin production increases, so does the sensitivity and a normal level is maintained. This is known as the disposition index. It is seen that this disposition index is significantly lower in women with PCOS regardless of whether they are obese or not. This disposition index is also considerably lowered by obesity, regardless of whether you have PCOS or not. So, when the two conditions combine, the disposition index is severely affected and the resistance of the body to insulin is much heightened.

The main question which arises in this regard is, can obesity cause PCOS? No clear answer can yet be given. However, a number of different points have been confirmed by extensive research. These are:

  1. Adipose tissue acts as an endocrine gland. Obesity leads to increased secretion of leptin and a decrease in the secretion of adiponectin. This combination increases insulin resistance and probably plays a role in increased secretion of androgen. These two together hamper ovulation and can lead to polycystic ovarian syndrome.
  2. Obesity also helps directly or indirectly in the development of several conditions which lead to a disruption of normal ovulation and hence to problems with pregnancy and conception. These are:
    1. It increases the production of estrogen
    2. It stimulates over-activity of the opioid system and the hypothalamus-pituitary-adrenal axis.
    3. In decreases the synthesis of the sex hormone binding globulins as the resistance of the body to insulin increases.
    4. It is related to high dietary lipid intake.

In women of reproductive age, as soon as the BMI crosses 24kg/sq mt, the risk of anovulatory infertility increases and goes on increasing with higher values of BMI.

The other side of the question is equally pertinent. This asks, does PCOS lead to the creation of obesity? Again, no conclusive answer exists to this question. Certain studies have shown that in women with PCOS, the adipose tissue prefers to accumulate in the abdomen, which increases the tendency towards obesity.

The pattern of obesity is also thought to play an important role in insulin resistance which in turn affects PCOS. Studies show that in men, body fat is mostly distributed in the upper body (android structure) while in women, fat tends to accumulate in the lower body (gynoid). In one study, Vague reported that women who have gynoid obesity have a higher prevalence of diabetes, hypertension and atherosclerosis than in women who have android obesity. These conditions, particularly diabetes are closely related to PCOS.

Finally, a number of studies have shown conclusively that even a small reduction in body weight in women with PCOS can lead to better endocrine profile, regular menstruation and healthy and normal pregnancy. A loss of 5% to 10% of total body fat can lead to a 30% reduction in central body fat, improvement of the sensitivity of the body to insulin and restore normal ovulation.

Interrelationship of obesity, PCOS and pregnancy

From the above discussion, it is now clear that PCOS tends to be worsened by obesity, though it is not caused by it. The two conditions are independent of each other, but if they do happen to occur together, they worsen the possibility of conception and lead to a greater probability of pregnancy complication and loss. Here are some important points to remark in this regard:

  • In a study in Spain, it was seen that PCOS is five times more prevalent in obese women compared to the general population.
  • Women who have PCOS or are obese have a higher risk of developing gestational diabetes. The risk is considerably heightened when both the conditions occur together. This can lead to several complications like preterm delivery, too large a baby, C-section and risk of developing type II diabetes later in life both by the mother and the baby.
  • Obesity has been linked to more frequent anovulatory cycles and infertility in women with PCOS. Such women have a higher rate of requiring the techniques of assisted reproduction.
  • Obesity also reduces the responsiveness of women to IVF treatments leading to a reduction in the rate of pregnancy. Jungheim demonstrated that when comparing a group of morbidly obese (BMI > 40) women with PCOS to another group which has PCOS but normal weight, it was seen that rate of pregnancy were seriously lower. Some difference was also noted in the rates of the live birth rates.
  • Obese people with PCOS are at a greater risk of miscarriage. This may be due to their effects on insulin which disturbs the normal ovarian function. Also, obese people with PCOS have elevated levels of plasminogen activator inhibitor-1 which increases the risk of miscarriage.