The risk of developing high blood pressure during pregnancy (gestational hypertension) is higher in pregnancies resulting from infertility treatments compared with those resulting from spontaneous conceptions.

The risk of preeclampsia is also elevated in assisted pregnancies, according to a study published in the medical journal Fertility and Sterility.

Pre-eclampsia is a condition that can affect multiple systems of the body and is characterized high blood pressure and protein in the urine (suggesting kidney failure). The condition occurs in up to 8 percent of pregnancies and accounts for up to 15 percent of the 500,000 pregnancy-related deaths world-wide each year.

Dr. Allen A. Mitchell, of Boston University, and colleagues studied over 5,000 women who gave birth to infants between 1998 and 2006. Within 6 months after delivery, the women were interviewed about sociodemographic and medical factors, including gestational hypertension, preeclampsia and infertility treatments.

Overall, 9.3 percent of the women reported having gestational hypertension and 2.6 percent reported having preeclampsia.

Women who had undergone infertility treatments had a higher rate of gestational hypertension than those who did not have infertility treatments, at 15.8 percent versus 8.9 percent, respectively. Women who had multiple fetuses were also more likely to have gestational hypertension than those carrying only one fetus (23 percent vs. 1.7 percent).

The risk of gestational hypertension in pregnancies resulting from infertility treatment was 90 higher than the risk in spontaneous pregnancies. The higher risk declined to 60 percent after accounting for the number of previous pregnancies and prepregnancy body mass index. Further analysis, factoring in the effect of multiple fetuses, reduced the risk to just 30 percent higher.

The preeclampsia risk among women with treated for infertility was more than twice as high compared with women without infertility treatments when a crude analysis was performed, Mitchell and colleagues report. After adjusting the data for other risk factors, the risk was only 60 percent higher and the inclusion of multiple fetuses changed the risk to only 20 percent.

The investigators conclude that the increased risk of gestational hypertension and preeclampsia in pregnancies resulting from infertility treatment is mostly explained by the higher frequency of pregnancies with multiple fetuses.