OHIO REPRODUCTIVE MEDICINE
Information for Patients
Is body weight associated with the ability to get pregnant?
The relationship of obesity with an increased risk for many health problems is well known, but to what extent is an excess of body fat in the way of having not only a pregnancy, but a healthy pregnancy and baby?
Most of the research has focused on women who do not ovulate consistently, typically manifested as having longer intervals between menstrual periods, or those women diagnosed with polycystic ovaries. For these women, it is known that if they are overweight or obese, losing weight is of great help in achieving ovulatory, and therefore potentially fertile, cycles.
What about women who have regular cycles, or even have a complete work-up for infertility that is apparently normal and yet they are not able to conceive?
Obesity has never been shown to be helpful when it comes to getting pregnant or having a healthy pregnancy. Furthermore, studies have shown that the fat tissue is very active in producing hormones and substances that can actually interfere with normal development and maturation of an egg, as well as with the preparation of the uterus where the embryo has to attach.
In animals, it has been shown that fat tissue can produce toxic substances, which may affect reproductive tissues. These toxins can affect the cells surrounding the egg, which in turn makes for lower quality of eggs. In mice, even a brief exposure of embryos to excess of palmitic acid (which is a fatty acid produced through the diet and by fat cells), can inhibit the normal growth of the fetuses.
Research done with the support of the National Institutes of Health (NIH) has tracked the lifestyle characteristics of thousands of nurses enrolled in a study (aka the Nurses Health Study II) and found that women whose dietary choices were based on vegetable sources of protein over animal products, with limited intake of trans-fats and refined carbohydrates had a significantly lower risk of infertility.
What about obese women who do get pregnant?
In pregnancy, most studies have found that obesity is associated with increased risk for miscarriage. Additionally, a significantly increased risk of preeclampsia, gestational diabetes, abnormalities of fetal growth, stillbirth, congenital abnormalities, and the need for cesarean section is found with obesity. All of this is true not only for obese women who conceive spontaneously but also for those who conceive after infertility treatments.
How can I know whether my weight is healthy?
The most common measure used for evaluation is the body mass index (BMI), which is easily calculated with the information about height and weight. You can calculate it here https://www.nhlbi.nih.gov/health/educational/lose_wt/BMI/bmicalc
BMI values
Between 25 and 29.9: overweight, with increased disease risk
Between 30 and 34.9: class I obesity, associated with high disease risk
Between 30 and 34.9: class II obesity, associated with very high disease risk
Above 40: class III obesity, associated with extremely high disease risk
What BMI should I aim for to maximize the chances of getting pregnant?
Above 18 and below 25 is the healthy range for general health and also for pregnancy purposes. In women who do not ovulate and are overweight or obese, a decrease in as little as 10% of their body weight can result in restoration of fertile cycles.
What else can I do to prepare myself for pregnancy? Here is a check list
– First, ask yourself when do you envision having a family, and remember that, even using the latest technology for IVF treatments, age alone is the main factor determining your success
– Keep a body weight as close as possible to the healthy range of BMI
– Avoid processed foods and artificial ingredients in your diet
– Do not smoke
– Treat any health condition that you may have
– Consider a genetic carrier screening test appropriate to your ancestry background
– Make sure you have immunity (a blood test to check antibodies) to infectious diseases such as rubella and varicella, and maintain safe sexual practices
– Make sure you have your annual ‘well woman’ ObGyn exam up to date
– Take a daily folic acid supplement or a prenatal vitamin at least 3 months in advance to the planned conception
– Keep yourself active with regular physical activities that you truly enjoy
– If you can, it is a great idea to schedule a preconceptional visit with your ObGyn. If you have a medical problem that may affect the course of your pregnancy, he or she may refer you to a Maternal Fetal Medicine specialist, in order to discuss how to improve the chances that you will have a successful and healthy pregnancy
Sources:
-Obesity and reproductive function. Jungheim E et al. Obstet Gynecol Clin North Am. 2012 Dec 39(4): 479–493
-Current knowledge of obesity’s effects in the pre- and periconceptional periods and avenues for future research. American Journal of Obstetrics and Gynecology, Dec 2010. E Jungheim, MD, MSCI; K Moley, MD