Blood vessels and in vitro fertilization

Assisted Reproductive Technology (ART) has advanced by leaps and bounds over the past decade. From advances in the drugs used to encourage fertilization to the techniques available to prepare embryos for implantation, the sciences is nothing short of amazing. Most amazing is the number of families that have benefitted from ART. One of the most advanced, interesting, and awesome forms of ART is In Vitro Fertilization (IVF). Although this technology enables many women to conceive who previously could not, the resulting pregnancies are at higher risk for complications. A growing body of research suggests that IVF pregnancies are at increased risk of complications that are related to placental dysfunction, such as preeclampsia.

Dr. Lee and her group of researchers at the Brigham and Women's Hospital in Boston, a Harvard Medical School affiliate, dug further into the relationship between IVF pregnancies and angiogenic markers, the proteins produced by the placenta that guide formation of blood vessels.  They measured the levels of two angiogenic markers that have been tied to preeclampsia: "soluble fms-like tyrosine kinase-1" (sFlt-1) and "placental growth factor" (PIGF) in pregnant women's blood during pregnancy. High levels of sFlt-1 and low levels of PIGF are linked to preeclampsia.

The authors collected samples from 2,392 singleton pregnancies, 108 of which were conceived through IVF. This was not a randomized trial (since it would be ethically and logistically impossible to randomize patients to spontaneous vs IVF conception), and there were baseline differences between women with IVF pregnancies and spontaneous pregnancies. IVF was associated with older maternal age, a history of never having been pregnant before, and white race. As in prior studies, IVF was associated with a higher risk of preeclampsia, 15.7% as compared to 7.7% in spontaneous pregnancies.

As one might have guessed, the levels of sFlt-1 were significantly higher and the levels of PIGF were significantly lower in IVF pregnancies as compared to spontaneous pregnancies. The differences remained significant, even when the researchers controlled for the differences between the groups, like age, race, and how many prior pregnancies they had. The differences were even significant if the researchers excluded women who developed preeclampsia. 

These findings suggest that angiogenesis, the way the blood vessels form, and the process of the placenta forming fundamentally differ between IVF and spontaneous pregnancies and these differences may account for the increase in obstetric complications. The authors suggest that obstetricians should take this increased risk into account and provide additional surveillance or caution when caring for pregnancies conceived through IVF.