Researchers have uncovered a surprising possible trigger for some preterm births: calcium buildup in the womb, similar to the kind that stiffens older people's arteries or causes kidney stones.
Ohio researchers studying more than 100 pregnant women found that when a mum-to-be's water breaks too early, the culprit seems to be abnormal calcium deposits that make the normally elastic amniotic sac prone to rupture.
It's a small study and more research is needed to prove if calcification really is behind this baffling kind of prematurity and if so, what to do about it.
But the research, reported on Wednesday in Science Translational Medicine, raises the possibility of investigating interventions.
"To have a new potential mechanism for one significant form of preterm birth is quite exciting," said Dr Edward McCabe, chief medical officer of the March of Dimes, who wasn't involved in the study.
Premature birth - being born before 37 weeks of pregnancy - can cause lifelong health problems, and babies who are very premature can die.
Sometimes there's an obvious cause for prematurity, such as an infection. Yet most of the time, doctors can't explain what triggers preterm birth in an otherwise healthy pregnant woman.
Dr Irina Buhimschi of Nationwide Children's Hospital took a closer look at a curiosity: Calcified plaques have often been spotted in placentas after birth - both preterm and full term - and no one knows why.
But abnormal calcification is well-known to play a role in a number of disorders.
Clusters of minerals, known as calciprotein particles, that float in the blood may be deposited in soft tissue instead of the skeleton, leading to such problems as artery-stiffening atherosclerosis or kidney stones.
Buhimschi's team found higher concentrations of the calcium-containing deposits in the amniotic sac when a mum's water broke prematurely than with full-term births or other types of preterm births.
"We've shown that formation of these particles in amniotic fluid is unhealthy, and we need to keep it in check," Buhimschi said.
