Meta-Analysis Links Obesity to Lower Assisted Reproduction Success

ORLANDO – Obesity puts a mom-to-be at greater risk for adverse pregnancy outcomes when she conceives through in vitro fertilization, according to a meta-analysis.

Significantly lower clinical pregnancy rates, a higher miscarriage risk, and lower live birth rates are each more likely when the body mass index (BMI) of a mother is greater than 30 kg/m², compared with normal weight mothers, according to a study presented at the annual meeting of the American Society for Reproductive Medicine.

Although previous researchers assessed BMI in women undergoing in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI), "the effect of obesity on IVF and ICSI remains unclear," Dr. Hassan Sallam said. "Some studies have found negative associations while others have not confirmed it."

Researchers who performed a previous systematic review of the literature cited "insufficient evidence" for any significant link between a higher BMI and IVF pregnancy outcomes (Hum. Reprod. Update 2007;13:433-44).

In search of a more definitive answer, Dr. Sallam and his colleagues decided to update the 2007 meta-analysis. With inclusion of more recent studies, obesity was associated with significantly worse pregnancy outcomes compared with women with a normal BMI (20-25) undergoing assisted reproduction. The current meta-analysis includes data from 15 controlled studies.

Six studies reported live birth rates, the primary outcome of the meta-analysis. Dr. Sallam and his associates found a live birth rate of 23% among obese women and 25% among normal weight controls, a statistically significantly difference (odds ratio, 0.85).

"Obese women undergoing IVF and ICSI have significant lower live birth rates and clinical pregnancy rates," said Dr. Sallam, professor of obstetrics and gynecology at the University of Alexandria in Egypt.

Of the eight studies that reported clinical pregnancy rates, 40.5% of obese women achieved pregnancy, compared with 43.8% of controls, also a statistically significant difference (OR, 0.88).

Obese participants also experienced significantly higher cancellation and miscarriage rates, Dr. Sallam said. In obese women, the cancellation rate was 8.7%, compared with 6.5% in controls (OR, 1.40). Miscarriages occurred in 21.9% of obese women vs. 19.3% of normal controls (OR, 1.22). Each of these factors was reported in five studies.

Not all outcomes were significantly different between obese and normal weight women. For example, 20.9% of obese women vs. 20.5% of controls achieved embryo implantation (OR, 1.03). The proportion of multiple pregnancies, likewise, was not statistically different: 21.5% of obese women versus 26.9% of controls (OR, 0.90). Dr. Sallam noted that only two studies each reported these outcomes.

"Whether obese women should be denied IVF ... is an open question," Dr. Sallam said. He cited a report from researchers who examined whether certain lifestyle changes should be mandated prior to IVF (Human Reprod. 2010;25:578-83). They specifically examined whether women at higher risk for poor outcomes due to obesity and alcohol or tobacco consumption should be required to make changes prior to receipt of assisted reproductive technology.

Dr. Sallam said he and his coauthors had no relevant financial disclosures.

ORLANDO – Obesity puts a mom-to-be at greater risk for adverse pregnancy outcomes when she conceives through in vitro fertilization, according to a meta-analysis.

Significantly lower clinical pregnancy rates, a higher miscarriage risk, and lower live birth rates are each more likely when the body mass index (BMI) of a mother is greater than 30 kg/m², compared with normal weight mothers, according to a study presented at the annual meeting of the American Society for Reproductive Medicine.

Although previous researchers assessed BMI in women undergoing in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI), "the effect of obesity on IVF and ICSI remains unclear," Dr. Hassan Sallam said. "Some studies have found negative associations while others have not confirmed it."

Researchers who performed a previous systematic review of the literature cited "insufficient evidence" for any significant link between a higher BMI and IVF pregnancy outcomes (Hum. Reprod. Update 2007;13:433-44).

In search of a more definitive answer, Dr. Sallam and his colleagues decided to update the 2007 meta-analysis. With inclusion of more recent studies, obesity was associated with significantly worse pregnancy outcomes compared with women with a normal BMI (20-25) undergoing assisted reproduction. The current meta-analysis includes data from 15 controlled studies.

Six studies reported live birth rates, the primary outcome of the meta-analysis. Dr. Sallam and his associates found a live birth rate of 23% among obese women and 25% among normal weight controls, a statistically significantly difference (odds ratio, 0.85).

"Obese women undergoing IVF and ICSI have significant lower live birth rates and clinical pregnancy rates," said Dr. Sallam, professor of obstetrics and gynecology at the University of Alexandria in Egypt.

Of the eight studies that reported clinical pregnancy rates, 40.5% of obese women achieved pregnancy, compared with 43.8% of controls, also a statistically significant difference (OR, 0.88).

Obese participants also experienced significantly higher cancellation and miscarriage rates, Dr. Sallam said. In obese women, the cancellation rate was 8.7%, compared with 6.5% in controls (OR, 1.40). Miscarriages occurred in 21.9% of obese women vs. 19.3% of normal controls (OR, 1.22). Each of these factors was reported in five studies.

Not all outcomes were significantly different between obese and normal weight women. For example, 20.9% of obese women vs. 20.5% of controls achieved embryo implantation (OR, 1.03). The proportion of multiple pregnancies, likewise, was not statistically different: 21.5% of obese women versus 26.9% of controls (OR, 0.90). Dr. Sallam noted that only two studies each reported these outcomes.

"Whether obese women should be denied IVF ... is an open question," Dr. Sallam said. He cited a report from researchers who examined whether certain lifestyle changes should be mandated prior to IVF (Human Reprod. 2010;25:578-83). They specifically examined whether women at higher risk for poor outcomes due to obesity and alcohol or tobacco consumption should be required to make changes prior to receipt of assisted reproductive technology.

Dr. Sallam said he and his coauthors had no relevant financial disclosures.

ORLANDO – Obesity puts a mom-to-be at greater risk for adverse pregnancy outcomes when she conceives through in vitro fertilization, according to a meta-analysis.

Significantly lower clinical pregnancy rates, a higher miscarriage risk, and lower live birth rates are each more likely when the body mass index (BMI) of a mother is greater than 30 kg/m², compared with normal weight mothers, according to a study presented at the annual meeting of the American Society for Reproductive Medicine.

Although previous researchers assessed BMI in women undergoing in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI), "the effect of obesity on IVF and ICSI remains unclear," Dr. Hassan Sallam said. "Some studies have found negative associations while others have not confirmed it."

Researchers who performed a previous systematic review of the literature cited "insufficient evidence" for any significant link between a higher BMI and IVF pregnancy outcomes (Hum. Reprod. Update 2007;13:433-44).

In search of a more definitive answer, Dr. Sallam and his colleagues decided to update the 2007 meta-analysis. With inclusion of more recent studies, obesity was associated with significantly worse pregnancy outcomes compared with women with a normal BMI (20-25) undergoing assisted reproduction. The current meta-analysis includes data from 15 controlled studies.

Six studies reported live birth rates, the primary outcome of the meta-analysis. Dr. Sallam and his associates found a live birth rate of 23% among obese women and 25% among normal weight controls, a statistically significantly difference (odds ratio, 0.85).

"Obese women undergoing IVF and ICSI have significant lower live birth rates and clinical pregnancy rates," said Dr. Sallam, professor of obstetrics and gynecology at the University of Alexandria in Egypt.

Of the eight studies that reported clinical pregnancy rates, 40.5% of obese women achieved pregnancy, compared with 43.8% of controls, also a statistically significant difference (OR, 0.88).

Obese participants also experienced significantly higher cancellation and miscarriage rates, Dr. Sallam said. In obese women, the cancellation rate was 8.7%, compared with 6.5% in controls (OR, 1.40). Miscarriages occurred in 21.9% of obese women vs. 19.3% of normal controls (OR, 1.22). Each of these factors was reported in five studies.

Not all outcomes were significantly different between obese and normal weight women. For example, 20.9% of obese women vs. 20.5% of controls achieved embryo implantation (OR, 1.03). The proportion of multiple pregnancies, likewise, was not statistically different: 21.5% of obese women versus 26.9% of controls (OR, 0.90). Dr. Sallam noted that only two studies each reported these outcomes.

"Whether obese women should be denied IVF ... is an open question," Dr. Sallam said. He cited a report from researchers who examined whether certain lifestyle changes should be mandated prior to IVF (Human Reprod. 2010;25:578-83). They specifically examined whether women at higher risk for poor outcomes due to obesity and alcohol or tobacco consumption should be required to make changes prior to receipt of assisted reproductive technology.

Dr. Sallam said he and his coauthors had no relevant financial disclosures.