The researchers matched 463 women who had miscarried at 6 to 12 weeks of pregnancy with 864 women at the same stage of pregnancy who had not miscarried.

• 研究者通过对463位孕妇因被动吸烟而在6-12周流产和843位相同孕龄妇女则没有出现该现象进行了配对研究。