Obesity is measured with BMI(Body Mass Index) by dividing weight in kilograms by the square of height in meters. A healthy BMI is considered to be between 18.5 and 24.9. having a BMI between 25 and 29.9 is considered ‘overweight’ and a BMI over 30 is considered ‘obese’.
Infertility is defined as the lack of pregnancy a er a year of purposeful, regular unprotected intercourse in women younger than 35 years. For women 35 years and older, infertility is diagnosed by the same criteria, but the time frame is shortened to 6 months.
Obesity is known risk factor for reproduction problems, but the mechanisms involved it is largely unknown. Obese women typically need increased levels of hormone medication to facilitate ovulation for conception. It is used to be thought that if an obese woman was able to ovulate ok, then the chances of conception was normal. We now know this is NOT true.
The prevalence of obesity is increasing significantly worldwide.3 Approximately 3,4 million adults die each year because of health problems associated with obesity and being overweight. Of these, 44% of the problems are related to diabetes, 23% to ischemic heart disease, and between 7% and 41% to some malignancies associated with overweight and obesity. It is postulated that a significant proportion of infertility cases are either directly or indirectly related to obesity.
The adverse effects of obesity on reproductive consequence are well known. However, it is difficult to describe the mechanism of how obesity is related to decreased fertility are complex and multifactorial.
If BMI is 35 the patient was 26% less likely to achieve a spontaneous pregnancy but the BMI over 40 the individual was 43% less likely to get pregnant.
Several mechanisms are involved in the relationship of fertility and obesity. The insulin resistance, insulin production and leptin levels are increased and results in hyperandrogenemia (excessive androgen production) in obese women.
Similarly, anovulation, changes in adipokine levels and the HPG axis, and steroidogenesis in obese women affects the reproductive system.
Obesity may deteriorate reproductive functions by affecting both the ovaries and endometrium. The HPG axis impairs because of changes in hormonal and some substrate levels. The levels of luteinizing hormone (LH), androstenedione, estrone, insulin, triglycerides, and very low density lipoprotein are increased and high density lipoprotein (SHBG- sex hormone binding-globulin)levels are decreased in obese women. Because of these changes, the HPG axis deteriorates and in turn lead to impaired folliculogenesis and follicular atresia.
There are various studies that supports the viewpoint that on biochemical level, obesity impacts oocyte quality and this is further compounded by obesity affecting uterine receptivity.
Fertility issues arising from obesity:
- Irregular menstrual cycles
- Problems with ovulation (reduced pregnancy rates and increased pregnancy complications like gestational diabetes, premature births, etc.)
- Increased androgen levels
- Polycystic ovarian syndrome (PCOS)- most common endocrine disorder among women
- Increased risk of miscarriage
- Decreased success rates of live births in both natural and assisted reproductive technologies (ART)
Though it is difficult to treat, there are some interventions ranging from minimally invasive lifestyle changes to higher-risk bariatric surgery help to decrease weight and increase fertility rates.
Healthy diet and increase in physical activity help to get better outcomes. Researchers have found that women in their early to mid-30s whose BMIs indicate obesity and who have experienced infertility for 2 or more years were able to achieve a 67% live birth rate after meaningful weight loss, defined as a loss of 10% of the baseline weight with health diet and continuous physical exercise.
Behavioural interventions: Health education, motivation or emotional support from health care providers may positively affect women’s success with weight loss and lifestyle changes.
Metformin is the choice of drug for infertility treatment in obese women. It decreases hepatic glucose production and intestinal absorption of glucose and improves insulin sensitivity. Other drugs like high doses of gonadotropins, clomiphene citrate, letrozole, etc are also effective.
Bariatric surgery can improve pregnancy outcome in obese women. It is indicated in persons with a BMI greater than 40 kg/m2 who do not have comorbidities or in those with a BMI greater than 35 kg/m2 who have diagnosed comorbidities such as chronic hypertension, type 2 diabetes, cardiovascular disease, sleep apnea, and stroke.5 ART (Assisted reproductive technologies) are also helpful for infertile women. However, There are some studies that show no or poor outcomes of this procedures among obese women.
Obese patients should be educated about the importance of pre-pregnancy weight reduction and should be encouraged to lose weight before the treatment to reduce the poor obstetrical outcomes.3 Though weight loss is primary treatment for infertile obese women, ART should not be delayed due to increasing age.3 Nonjudgmental and unbiased care will help women achieve healthier outcomes for themselves and their offspring.