It's no secret that smoking during pregnancy is extremely harmful to both mother and baby, and new research has identified even more risks.

The findings suggest smoking while pregnant can cause chemical changes to the fetus as early as 12 weeks. These change could predispose the unborn child to a number of health conditions that they will battle throughout their lives, a the University of Aberdeen reported.The behavior causes changes in chemical tags called epigenetic marks, which are attached to DNA and influence how genes function.

"We identified changes in DNA methylation of genes which are crucial for the growth and development of a baby when a mother smokes," said Professor Paul Fowler, from the University of Aberdeen who led the Medical Research Council funded project. "These findings strengthen and extend previous studies by showing that such changes are detectable during second trimester development. This is a clear demonstration that maternal smoking early in pregnancy can [program] incorrect development of the liver, which is a vital organ both in the [fetus] and, of course, after birth.

Despite the known dangers associated with smoking during pregnancy, about 25 percent of pregnant women are smokers and fewer than 4 percent quit while expecting. The newly-identified genetic changes associated with smoking can make the baby more susceptible to disease such as obesity, cognitive problems, cardiovascular disease, and asthma. The findings also show fetuses of mothers who smoked showed liver changes, such as male livers looking more like organs belonging to a female.

"This is the first time such changes have been detected so early in pregnancy and this study demonstrates another way in which the burden of maternal smoking persists into adulthood, with these babies more likely to grow up to be obese and diabetic," Fowler concluded.

The findings were published in a recent edition of the journal BMC Medicine.