Obesity and Contraception: Emerging Issues

Amitasrigowri S. Murthy, M.D., M.P.H., F.A.W.G.

Disclosures

Semin Reprod Med. 2010;28(2):156-163. 

In This Article

Consequences of Obesity

Obesity has been linked to a multitude of disorders.[5–7] The risk of developing type 2 diabetes increases as BMI increases from 22 kg/m2. Visceral or central obesity is associated with insulin resistance. Increased body mass also increases the risks of hypertension, coronary artery disease, and stroke. With every increase of 10% in weight, blood pressure increases 6 mm Hg systolic and 4 mm Hg diastolic.[8] Obstructive sleep apnea is due to both mechanical obstruction (changes in upper airway dimensions as well as reduction of lung volume) and to impaired muscle tone of the neck. Osteoarthritis is the most common degenerative disease associated with obesity and may decrease mobility. The increase in risk of breast, colon, and endometrial cancer in obese women is thought to be mediated by excess fat leading to an alteration in the metabolism of sex steroids and insulinlike growth factor 1.[9] The psychosocial effects of obesity include discrimination in work, the risk of less education, and impaired social relationships.[8]

Before pregnancy, obesity has a negative effect on fertility, primarily by reducing ovulation frequency. Ovulatory dysfunction may be caused by insulin resistance and the resulting hyperinsulinemia. High levels of insulin have a negative influence on the liver's production of sex hormone-binding globulin (SHBG), leading to increases in testosterone and dihydrotestosterone. Increases in adipose tissue lead to chronically elevated levels of estrogen, from peripheral conversion of the high circulating androgens to estrogen. High insulin levels can cause augmentation of the ovarian response to luteinizing hormone and thereby causes ovarian thecal cell production of androstenedione, which, along with the increased free testosterone from decreased SHBG, can impair normal ovulatory function.[10] Normal ovulatory function is further disrupted by leptin, which is secreted by adipocytes and decreases hunger and food intake. Leptin also causes inhibition of ovarian follicular development and steroidogenesis.[11]

Obese women have decreased fecundity; the probability of natural conception is decreased by 4% with a BMI >29 kg/m2. The effects of obesity on fertility have been corroborated by data from the 2002 National Survey of Family Growth (NSFG). Higher rates of unintended pregnancy among obese women were expected, due to possible higher rates of contraceptive failure. The NSFG in fact revealed no increased rate of unintended pregnancy among those who are obese and actually hinted at levels of subfertility, consistent with the theory of interference with normal ovulatory function.[12,13]

Prepregnancy obesity has increased risks of poor pregnancy outcomes, for both the woman and the fetus. Maternal effects are caused by the associated metabolic changes with obesity, like gestational diabetes and pregnancy-induced hypertension. Other effects of obesity include increased rates of fetal neural tube defects, possibly due to metabolic disturbances or nutritional deficiencies, as well as complications from amniocentesis.[8] Obesity has also been associated with increased risk of pregnancy loss. When examining a database of women undergoing assisted reproductive technology for pregnancy, a higher pregnancy loss rate was noted among obese women (odds ratio [OR]. 1.69; 95% confidence interval [CI], 1.13 to 2.51) as well as a lower live birthrate (OR, 0.75; 95% CI, 0.57 to 0.98).[10] Another retrospective analysis suggested that the rate of spontaneous abortion rises progressively with increases in BMI (overweight OR, 1.29, to very obese OR, 2.19).[10] Obese women also have increased rates of stillbirth and neonatal death.[10]

Intrapartum complications stem from labor induction and performance of cesarean delivery. Two different studies reported increased rates of cesarean deliveries in obese women when compared with nonobese women.[10] Rates of labor induction in obese women were doubled when compared with normal weight women. Decreased amplitude and frequency of contractions might be explained by an inhibitory effect on the contractility of the myometrium by leptin. Women with a BMI >34 have been reported to have a threefold increase in the rate of cesarean delivery when compared with matched controls with normal BMI.[14,15] Surgical procedures may be technically difficult as well. When performing open surgery, access to the pelvis can be limited, especially when using a Pfannenstiel incision. A large pannus may need to be manually retracted; longer instruments and difficulty reaching the pelvis may require longer operating times and an experienced surgeon. In addition, larger blood loss amounts, as well as increased risk of trauma to nearby organs, can make surgery difficult. Late complications of surgery are increased in obese women, including wound infection, pulmonary infections, and venous thromboembolism (VTE).[15] Fetal effects include macrosomia, birth defects, and future juvenile obesity.[16]

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