Teenagers who were conceived through assisted reproductive technologies, including in vitro fertilization (IVF), may be six times more likely to have hypertension compared to those who were conceived naturally, according to new research.
Researchers from the University Hospital in Bern, Switzerland, said this is the first evidence of its kind.
“There is growing evidence that artificial reproductive technologies alters the blood vessels in children, but the long-term consequences were not known,” said the lead author of the study, Dr. Emrush Rexhaj.
“We now know that this places ART children at a six times higher rate of hypertension than children conceived naturally,” Rexhaj said.
Hypertension, or high blood pressure, puts an individual at a higher risk of heart disease and stroke.
Assisted reproductive technologies (ART), including IVF, were developed in 1978 and have helped millions of people who cannot have children naturally. The most common ART methods are IVF and intracytoplasmic sperm injection (ICSI).
The findings supported earlier evidence from animal studies, where mice were found to have premature aging of the blood vessels and subsequently hypertension.
The researchers followed 97 teenagers in total—54 of whom were born through ART, and 43 of whom born naturally. The teenagers in the study were all aged 16 to 17.
The teenagers born through ART had an average blood pressure of 119/71, while those who had been born naturally had a slightly lower average of 115/69.
The first figure is systolic, and the second is diastolic pressure, which are maximum and minimum pressures, respectively. The systolic pressure coincides with each heart beat while diastolic pressure is measured when arteries relax between the beats.
The authors proceeded to see who would be diagnosed as having clinical hypertension, that is, a reading of more than 130/80.
Eight out of the 54 ART teens—that is, 14.8 percent—had clinical hypertension, whereas only one out of the 43 naturally conceived teens—or 2.3 percent—had hypertension. Dividing 14.8 by 2.3 gives 6.4—the figure the authors said is the heightened risk of someone who was born through ART would have for hypertension.
Five Years Ago
According to the authors, the same group of children had been studied five years ago, then aged 11 to 12. No major differences in blood pressure between ART and naturally conceived children were found at the time.
“It only took five years for differences in arterial blood pressure to show,” Rexhaj said.
“This is a rapidly growing population (ART-conceived individuals) and apparently healthy children are showing serious signs of concern for early cardiovascular risk, especially when it comes to arterial hypertension (high blood pressure),” he added.
Limitations and Implications
The study acknowledged several limitations, including that all the participants were taken from one birth center, and that only single-birth children were studied.
“Whilst I laud the efforts to monitor health, this should be done on a population basis not with small biased studies like this one,” said IVF expert professor Alaistar Sutcliffe of the University of London told The Telegraph.
The study had excluded factors that would heighten cardiovascular disease from the study, including premature babies, low birth weight, and pre-eclampsia.
But, noting the above exclusions, Dr. Larry Weinrauch said in an accompanying editorial in the same journal that the study’s small cohort may downplay the significance of increased blood pressure found in ART-conceived teenagers.
“Early study, detection and treatment of ART conceived individuals may be the appropriate course of preventative action,” Weinrauch said. “We need to be vigilant in the development of elevated blood pressure among children conceived through ART to implement early lifestyle-based modifications and, if necessary, pharmacotherapy.”
Emeritus professor in Developmental Biology, Tom Fleming, told The Telegraph that since IVF has only been around for 40 years, the majority of those born have not reached middle age, where cardiovascular conditions often arise. As such, Fleming believes more evidence may become available in the future.
“From a biological perspective, the early embryo is known to be sensitive to environmental conditions that may alter how it develops, affecting later gene expression and physiological condition, and may lead to changes such as hypertension,” he told The Telegraph.