The adverse effects of obesity on fertility and pregnancy outcomes are overwhelming and indisputable. Body mass index (BMI) in kg/m2 is calculated from maternal height and weight data. Morbid obesity is defined as BMI over 40; Obesity is defined as BMI over 30. In obese women with excessive adipose tissue, abnormal hypothalamic and pituitary hormone secretions are common, leading to anovulation and infertility.

Obesity is strongly related to polycystic ovarian syndrome (PCOS) in women. Obese women are also particularly susceptible to diabetes and insulin resistance. Women with PCOS and/or obesity often have irregular menstrual cycles and infertility because they usually don’t ovulate. Researchers have determined that most women with PCOS and/or obesity have an endocrine imbalance known as “insulin resistance” in which the body doesn’t handle insulin normally. Women with insulin resistance may have normal blood glucose levels, but because the cells of their bodies are resistant to insulin, the body over compensates by producing even higher levels of insulin to keep their blood glucose levels normal. The resulting higher insulin levels lead to more fat storage (obesity) and also disrupt proper ovarian hormone production (increased male hormone), thus preventing ovulation. Even with fertility drugs or in vitro fertilization (IVF) treatments, pregnancy rates are adversely affected by obesity.

When obese women are able to correct the insulin resistance with proper diet, exercise, vitamins (Inositol) and/or insulin-sensitizing drugs, such as metformin (Glucophage), normal ovarian function (ovulation and normal female hormone production) often returns. Use of metformin, Inositol, regular exercise and/or weight loss of 5-10% of body weight can each independently lead to occasional spontaneous pregnancies, but can also dramatically improve pregnancy rates with all fertility treatments. Fewer pregnancy complications and better perinatal outcomes are also seen.

Obesity also poses more risks for women undergoing IVF treatments. Today almost all IVF centers are freestanding, outside of hospitals. IVF egg retrievals are performed under conscious sedation.

Conscious sedation is a drug induced depression of consciousness and individuals can respond purposefully to verbal commands. No interventions are required to maintain a patent airway and spontaneous ventilation is adequate. The most critical part of patient care is providing for patient safety during the time the patient is sedated. Obese patients are at increased risk for complications such as over-sedation, under-sedation, respiratory insufficiency, hypoxemia (decreased oxygen in the blood), airway obstruction, and aspiration of stomach contents. Aspiration, although rare, is the most common cause of death secondary to conscious sedation. Proper patient selection involves recognition of risk factors that may place the patient at increased risk for complications and is critical to safe patient care. In addition, for women with a BMI > 40, the egg retrieval technique is more challenging, difficult and dangerous. For this reason, many IVF centers have imposed various cutoffs for BMI and IVF egg retrievals under conscious sedation. Some women with a BMI over 40 (morbid obesity) may not be able to proceed to egg retrieval and conscious sedation. At Fertility Centers of Illinois any obese women with a BMI over 35 must obtain counseling regarding the increased risks to both the mom and baby, and provide authorization to proceed with IVF in light of the risks. In addition, any woman whose BMI is between 40-50 may proceed with IVF and anesthesia, as long as they pass medical clearance and anesthesia clearance. A consultation with a Maternal Fetal Medicine specialist may also be required to discuss potential risks to mom & baby. Because of the heightened associated risks, patients with a BMI over 50 will not be permitted to proceed with fertility treatment.

Many studies confirm that morbidly obese women who do conceive have an increased risk of pregnancy complications and adverse perinatal outcomes. These complications include:

  • pre-eclampsia,
  • antepartum stillbirth,
  • higher C section rates/complications
  • shoulder dystocia
  • meconium aspiration
  • early neonatal death
  • diabetes mellitus
  • birth defects involving the brain, heart and neural tube defects.

The take home message from these studies is that women need to be counseled about the serious dangers associated with obesity and pregnancy complications. Obesity is a chronic but treatable condition. The problem of obesity can be solved, but requires motivation, counseling, and behavior modification. On occasion, for the morbidly obese, medications and/or bariatric surgery may be necessary. I encourage primary care physicians and OB/GYNs to seriously discuss nutrition and weight loss with obese women before and during pregnancy in order to reduce complications.