Tiny carbon particles, possibly present in fumes from petrol and diesel vehicles, have been discovered in placentas from mothers of babies born in London, new research has suggested.
The research, carried out by researchers at Queen Mary University London, provides evidence of a possible mechanism of how babies are affected by pollution while being theoretically protected in the womb, experts have suggested.
Previous research has suggested that there are links between pregnant mothersâ€™ exposure to air pollution and premature birth, low birth weight, infant mortality and childhood respiratory problems.
The latest study, which was presented at a conference in Paris this weekend suggests that sooty particles are able to reach the placenta via the bloodstream.
The work was presented by Dr Norrice Liu, a paediatrician and clinical research fellow, and Dr Lisa Miyashita, a post-doctoral researcher, both members of the Universityâ€™s Blizzard Institute.
Dr Miyashita said: â€œWeâ€™ve known for a while that air pollution affects foetal development and can continue to affect babies after birth and throughout their lives.
â€œWe were interested to see if these effects could be due to pollution particles moving from the motherâ€™s lungs to the placenta. Until now, there has been very little evidence that inhaled particles get into the blood from the lung.â€
The researchers worked with five pregnant women who were all living in London and due to have planned caesarean section deliveries at the Royal London Hospital.
All of the mothers were non-smokers with an uncomplicated pregnancy and each one gave birth to a healthy baby. The women all gave permission for researchers to study their placentas after delivery.
The team was interested in particular cells called placental macrophages. Macrophages exist in many different parts in the body. They are part of the bodyâ€™s immune system and work by engulfing harmful particles, such as bacteria and pollution particles. In the placenta they also help to protect the foetus.
The team studied a total of 3,500 placental macrophage cells from the five placentas and examined them under a high-powered microscope. They found 60 cells that between them contained 72 small black areas that researchers believe were carbon particles.
They went on to study the placental macrophages from two placentas in greater details using an electron microscope and again found material that they believe was made up of tiny carbon particles.
Dr Liu added: â€œOur results provide the first evidence that inhaled pollution particles can move from the lungs into the circulation and then to the placenta.
â€œWe do not know whether the particles we found could also move across into the foetus, but our evidence suggests that this is indeed possible. We also know that the particles do not need to get into the babyâ€™s body to have an adverse effect, because if they have an effect on the placenta, this will have a direct impact on the foetus.â€