SALT LAKE CITY – Women who are obese should receive more than 5,000 IU of human chorionic gonadotropin (HCG) to trigger final oocyte maturation during in vitro fertilization, findings of a retrospective cohort study suggest.
Fully 23% of obese women had low beta-HCG levels the day after receiving a 5,000 IU HCG trigger dose, compared with 1% of non-obese women (odds ratio, 21.4; 95% confidence interval, 15.0-30.4), reported Mohamad Irani, MD, and his associates from Cornell University, New York. In contrast, 10,000 IU HCG triggered adequate beta-HCG levels in 81% of obese patients with a BMI of 30-40 kg/m2, and in 90% of those whose BMI exceeded 40 kg/m2.
Low beta-HCG levels decreased the chances of oocyte maturation, fertilization, and live birth in the study. “Patients’ BMI should be taken into consideration when determining the dose of HCG trigger,” the investigators concluded in a poster presented at the annual meeting of the American Society for Reproductive Medicine.
Patients with hypothalamic amenorrhea or who are undergoing stimulation with a gonadotropin-releasing hormone (GnRH) agonist are not candidates for a GnRH-agonist trigger and therefore need to receive HCG instead, the researchers noted. To understand how the dose of HCG affects the chances of final oocyte maturation, they studied 19,084 HCG trigger recipients at their center between 2004 and 2013.
By protocol, patients received 10,000 IU HCG if their serum estradiol (E2) level was less than 1,500 pg/mL on the day of trigger; 5,000 IU if it measured 1,501-2,500 pg/mL; 4,000 IU if it was 2,501-3,000 pg/mL; and 3,300 IU if it exceeded 3,000 pg/mL.
The day after HCG trigger, 18,666 patients had beta-HCG levels of at least 50 mIU/mL, while 418 patients had low beta-HCG levels of less than 50 mIU/mL. A comparison of the two groups showed that low beta-HCG was associated with significantly lower rates of oocyte maturation (77% vs. 81%; P less than .001) and fertilization (63% vs. 72%; P less than .001). It was also associated with more than a 30% lower chance of a live birth (adjusted OR, 0.67; 95% CI, 0.5-0.8), even after accounting for age, and the stage and number of embryos transferred.
The researchers also examined response to HCG trigger among non-obese patients. Among patients who were overweight (BMI 25 to 30 kg/m2), the chances of a low beta-HCG level the day after trigger were 14% when the HCG dose was 3,300 IU, 12.5% when it was 4,000 IU, 4.3% when it was 5,000 IU, and 0.4% when it was 10,000 IU.
Among healthy-weight patients (BMI 18.5-25 kg/m2), low beta-HCG levels occurred 3.6% of the time when the HCG dose was 3,300 IU, 2.3% of the time when it was 4,000 IU, 0.6% of the time when it was 5,000 IU, and 0.08% of the time when it was 10,000 IU. Notably, these same doses triggered adequate beta-HCG levels in all 660 patients who were underweight (BMI less than 18.5 kg/m2), the researchers reported.
Dr. Irani reported having no relevant financial disclosures.