Low Birth Weight May Be Risk for Developing High Blood Pressure
Poulter says he cannot describe the mechanism. "In dizygotic [fraternal] twins -- they have separate placentas -- it may be that one just implanted better than the other. In the monozygotic [identical] twins, they share the same placenta, but one artery from the baby to the placenta was bigger than the other; it was just an unequal distribution of the goodies," he says.
The second study, led by Terence Dwyer, a professor at the University of Tasmania, studied the association between blood pressure and birth weight by analyzing data from almost 900 eight-year-old children. The researchers found that blood pressure decreased with birth weight and increased with current body mass.
Like Poulter, Dwyer and colleagues list unequal distribution of nutrients and oxygen as a possible factor that could be associated with birth weight and blood pressure. They write that reduced nutrient and oxygen availability could lead to permanent adverse programming of the cardiovascular system.
Finally, words of caution from Poulter. "We are not saying maternal smoking [isn't responsible] for small babies; we are not saying that diet doesn't affect the size of the baby," he says. "What we are saying is that it isn't those maternal [factors] which produce a spurious association between birth weight and blood pressure; it is a real association, independent of what the parents do."
"And this also doesn't say that if you're born small, you've had it, you are bound to get hypertension [high blood pressure], or if you are born fat you are bound not to get hypertension," cautions Poulter. "It in no way suggests that the major environmental factors aren't still very valid."