Some 25 percent of women who miscarried had been exposed to tobacco, they found.
The study, which surveyed 463 women, said second hand smoke increases the risk of miscarriage by 67 percent, while active smoking doubles the risk. The study did not say what it is in tobacco that causes the miscarriages, however.
“Our results say that pregnant women should avoid as much as possible staying in environments where they can be exposed to tobacco smoke,” said Lena George, a researcher on the study, according to Upsala Nya Tidning.
The study measured the amount of cotinine in the blood. The substance builds up when the body breaks down nicotine and appears in large amounts in active smokers.
For those who do not smoke the amount is very low. George said this was the first Swedish study to measure the amount of cotinine in the blood and is clear evidence that passive smoke increases the risk of miscarriage.