Kids born through in vitro fertilization may be more likely to develop high blood pressure, a new study suggests.
Researchers found a higher average blood pressure among teens born through IVF than in children conceived naturally, according to a report in the Journal of the American College of Cardiology.
Moreover, teens born through IVF were more likely to have blood pressures high enough to be diagnosed with hypertension.
The researchers advise parents of children conceived with IVF to concentrate on other heart disease risk factors.
"Eliminate additional cardiovascular risk factors, such as overweight, sedentary lifestyle and smoking," suggests coauthor Dr. Urs Scherrer of the University of Bern, Switzerland. Also, he recommends, get a 24-hour blood pressure reading when the children are between ages 16 and 20.
Scherrer and colleagues compared 54 teens conceived through IVF with 43 of their friends who had been conceived naturally. The teens' average age was 17.
In adults, a blood pressure above 120/80 is considered high. But in children and adolescents, a normal blood pressure depends on age and height. If a youngster has a higher blood pressure than 90% to 95% of other males or females his or her age and height, then the child may have high blood pressure.
The IVF teens had higher blood pressure, on average, than their friends (119/71 versus 115/69). Eight of the IVF teens were diagnosed with hypertension, compared to one in the control group.
Five years earlier, researchers had checked blood pressures in both groups and found no difference between IVF teens and their friends. "Until adolescence there are no cardiovascular problems," Scherrer said by email.
The conditions under which IVF embryos develop may play a role, he suspects.
"There are numerous conditions which are not physiologic during the in vitro period - temperature, mechanical insults related to embryo handling, sub-optimal culture media, etc. - that the embryo needs to cope with in order to survive, (and these) may have altered the regulation of gene (expression)," Scherrer said.
While the new findings are very interesting, the study is small, said Dr. Alan Penzias, an associate professor of obstetrics, gynecology and reproductive biology at the Harvard Medical School and a fertility specialist at Boston IVF.
Findings of small studies are not always generalizable to the population at large, Penzias said by email.
And while the researchers may have mitigated a number of possible confounders by using the IVF children's friends as controls - the control group was probably the best match for socioeconomic background, for example - they didn't eliminate what might have been the biggest variable: history of infertility, Penzias said.
"Is the finding in this paper caused by the IVF procedure or is it caused by the infertility itself," Penzias asked.
Penzias points to a large 2012 study in the New England Journal of Medicine that found a higher risk of birth defects in babies born to couples with a history of infertility, regardless of whether the babies were conceived naturally or with IVF.
Still, Penzias said, "tracking the outcomes of medical intervention is prudent. Deciphering the mechanisms of disease to facilitate the design of treatments that improve the human condition is a worthy mission and is one that is universally endorsed."