Turns out, soot from polluted air can affect the placenta.
According to a recent research, evidence of tiny particles of carbon, typically created by burning fossil fuels, has been found in placentas for the first time.
The new study adds to existing evidence on the dangers of pollution for unborn babies and suggests that when pregnant women breathe polluted air, sooty particles are able to reach the placenta via the bloodstream.
Dr. Norrice Liu, lead researcher of the study said, "We've known for a while that air pollution affects fetal development and can continue to affect babies after birth and throughout their lives. We were interested to see if these effects could be due to pollution particles moving from the mother's lungs to the placenta. Until now, there has been very little evidence that inhaled particles get into the blood from the lung."
The researchers worked with five pregnant women who were all living in London and due to having planned cesarean section deliveries at the Royal London Hospital. They were all non-smokers with an uncomplicated pregnancy and each one gave birth to a healthy baby.
The researchers were interested in particular cells called placental macrophages. Macrophages exist in many different parts of the body. They are part of the body's immune system and work by engulfing harmful particles, such as bacteria and pollution particles. In the placenta, they also help to protect the fetus.
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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. On average, each placenta contained around five square micrometers of this black substance.
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.
"Our results provide the first evidence that inhaled pollution particles can move from the lungs into the circulation and then to the placenta.
"We also know that the particles do not need to get into the baby's body to have an adverse effect because if they have an effect on the placenta, this will have a direct impact on the fetus."
Professor Mina Gaga, President of the European Respiratory Society (not involved in the study) said, "Previous research shows that pregnant women living in polluted cities are more prone to pregnancy issues such as restricted fetal growth, premature birth, and low birth weight babies. This new research suggests a possible mechanism for how babies are affected by pollution while being theoretically protected in the womb. This should raise awareness amongst clinicians and the public regarding the harmful effects of air pollution in pregnant women."
The study was presented in a meeting at State of the Science Congress on Nursing Research.