Researchers found that women with a prior IVF-conceived pregnancy showed higher large artery stiffness up to five years after delivery, offering new insights into how assisted reproduction may influence long-term maternal cardiovascular health.
Study: Large artery stiffness is elevated in women with a prior pregnancy conceived via in vitro fertilization. Image credit: NDAB Creativity/Shutterstock.com
A new study published in the Journal of Applied Physiology reveals that women who conceive through in vitro fertilization may have elevated large artery stiffness after childbirth.
Cardiovascular health after IVF pregnancies
Infertility refers to the inability to achieve a successful pregnancy due to medical, sexual, reproductive, or age-related complications. In women, infertility is associated with an increased risk of cardiovascular disease.
In vitro fertilization (IVF) is the most widely used assisted reproductive technology for treating infertility. More than ten million children have been born through this technique worldwide since 1978. However, existing evidence suggests that IVF may increase cardiovascular disease risk in women.
Vascular dysfunction, characterized by large elastic artery stiffening and endothelial dysfunction, is significantly associated with the pathogenesis of cardiovascular disease. Although an increased risk of vascular dysfunction has been observed in women with infertility, evidence on the influence of IVF processes on vascular dysfunction is largely lacking.
In pregnancies conceived via IVF, an increased risk of stroke and new-onset hypertension has been observed for up to five years after delivery. Given the possibility that potential cardiovascular changes may occur during this postpartum period (the period after childbirth), researchers at the University of Colorado Anschutz Medical Campus, USA, assessed vascular function in women who conceived either spontaneously without medical assistance or via IVF and gave birth within the past one to five years.
Women with prior IVF showed stiffer large arteries
The study enrolled 24 women with spontaneous pregnancy (control group) and 15 women with IVF-mediated pregnancy. Participants from both groups had comparable age, body fat percentage, and resting blood pressure. Participants’ large artery stiffness and endothelial function were assessed at rest as measures of vascular dysfunction.
The assessments revealed significantly greater large-artery stiffness in the IVF group than in the control group. However, no differences in endothelial function were observed between the groups.
To search for potential mechanisms that might contribute to the observed changes, large arteries of experimental mice were incubated with serum samples collected from eleven participants from each group. This was done to assess the influence of circulating factors on elastic modulus, a measure of inherent stiffness of large arteries.
The analyses showed a 28% higher elastic modulus in mice treated with serum samples from the IVF group compared to mice treated with the control group serum samples. However, this difference did not reach statistical significance. These findings suggest that circulating factors may contribute to large artery stiffness.
Further analysis of several circulating factors, including oxidative stress- and inflammation-related biomarkers and hormones, revealed that the concentration of follicle-stimulating hormone (FSH) was higher in the IVF group, although still within the expected range for premenopausal women, and that the concentration of this hormone was positively associated with in vivo large artery stiffness.
FSH may contribute to artery stiffness
This study is the first to report that women with a prior IVF-conceived pregnancy had higher large artery stiffness one to five years after delivery than women who conceived without medical assistance. The findings also point to a possible role for circulating follicle-stimulating hormone (FSH), which was higher in the IVF group and was associated with greater artery stiffness.
FSH is a hormone produced by the pituitary gland that regulates sexual development and reproduction by controlling ovarian function in women and testicular function in men.
Previous research has also linked higher circulating FSH levels to vascular function in healthy women. One proposed explanation is that elevated FSH may alter blood flow patterns within arteries, increasing oscillatory (back-and-forth) and retrograde (backward) blood flow, changes that have previously been associated with impaired vascular function. However, because endothelial function did not differ between the two groups in the current study, these mechanisms are unlikely to fully explain the findings.
Further research is needed to determine whether FSH directly contributes to increased artery stiffness following IVF pregnancies or whether other circulating factors are involved.
Why endothelial function remained unchanged
Although women with prior IVF pregnancies had stiffer large arteries, the researchers found no evidence of impaired endothelial function. They suggest this may reflect the protective effects of estradiol, a hormone known to help maintain healthy blood vessels, or compensatory changes in circulating factors or proteins expressed by endothelial cells.
The research team has previously shown that estradiol may protect premenopausal women against oxidative stress-related vascular dysfunction. In the current study, women in the IVF group also had higher total antioxidant status, although the difference was not statistically significant, suggesting that additional biological mechanisms likely contribute to the observed increase in arterial stiffness.
Potential cardiovascular changes after IVF
These findings suggest that endothelial function remained preserved in women with IVF-conceived pregnancies and was therefore unlikely to be the primary factor contributing to the elevated large artery stiffness observed in the study.
However, because the study was cross-sectional, it could not determine whether IVF or the associated circulating factors directly caused these vascular changes. In addition, although the researchers matched the two groups for pregnancies complicated by hypertensive disorders to reduce potential confounding, the study was not large enough to determine whether hypertensive disorders of pregnancy, either alone or in combination with IVF, influenced vascular function.
Future studies that consider these potential confounding factors are needed to conclusively determine whether circulating FSH and other factors directly contribute to large-artery stiffness in IVF pregnancies.
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