Insulin resistance may be an independent risk factor for spontaneous abortion in women who undergo treatment for infertility, Dr. Li Tian of Beijing University and colleagues reported.
The researchers examined the incidence of spontaneous abortion among ethnic Chinese patients who became pregnant following assisted reproductive technology (ART) treatment at the Reproductive Medicine Centre of Beijing University. The study population consisted of 107 patients who successfully conceived, among 327 women who underwent in vitro fertilization or intracytoplasmic sperm injection at the clinic from June 2003 to July 2005 (J. Clin. Endocrinol. Metab. 2007 Jan. 23 [Epubl doi:10.1210/jc.2006–1123]).
All patients undergoing ART treatment were tested for insulin resistance before initiating pituitary suppression with a gonadotropin-releasing hormone agonist prior to follicle-stimulating hormone/human chorionic gonadotropin stimulation. Insulin resistance was defined using a homeostasis model, and calculated as the product of fasting insulin and fasting glucose concentrations, divided by 22.5. Patients with an insulin resistance index of greater than 4.5 were considered to have insulin resistance.
The mean age of the study population was 30.8 years (range: 21–39 years), and mean body mass index (BMI) was 22 (range: 16–33). Nineteen women were considered obese, with a BMI of 25 or greater, and 13 women had polycystic ovarian syndrome (PCOS). None of the women had type 2 diabetes, but 23 patients were considered insulin resistant.
Nineteen patients (17.8%) experienced spontaneous abortion. Eleven of 23 patients with insulin resistance (47.8%) had spontaneous abortion, compared with 8 of 84 patients without insulin resistance (9.5%). Overall, patients with insulin resistance had a greater than eightfold increased risk of spontaneous abortion, compared to patients without insulin resistance (odds ratio, 8.32).
In logistic regression analysis, advanced age (35 years or older), high BMI (25 or greater), and PCOS were all factors positively associated with increased risk of spontaneous abortion, but none was associated with significantly increased odds ratios. Only insulin resistance was significantly associated with increased risk of spontaneous abortion, and the association remained significant after controlling for possible confounding effects of advanced age, high BMI, and PCOS.
“Increased insulin resistance may be an independent risk factor for spontaneous abortion after ART treatment,” concluded the study authors. “Patients with high insulin resistance should be advised before ART treatment regarding the need of weight reduction or taking metformin, in order to reduce their risk of spontaneous abortion.”
The authors reported no conflicts of interest.