NEW YORK (Reuters Health) - It is not uncommon for expectant mothers to feel anxious and depressed, new research shows, and these feelings can have serious consequences for mom and baby.

"Mental health problems in the postpartum period have received much attention in the past decade," Dr. Antoinette M. Lee of the University of Hong Kong told Reuters Health, whereas mental health problems in the period before birth, known as the antenatal period, have received considerably less attention.

"Our study," Lee said, "shows that anxiety and depression during pregnancy should also not be overlooked, given that both are highly prevalent and strongly associated with postpartum depression."

Among a consecutive sample of 357 pregnant women, Lee andcolleagues found that more than half (54 percent) had anxiety and more than one third (37 percent) had signs of depression at some point during their pregnancies.

Anxiety was more prevalent than depression at all stages of pregnancy. Between 12 and 17 percent of women in the study were found to have both anxiety and depression at various stages of pregnancy, the researchers report in the medical journal Obstetrics and Gynecology.

Both antenatal anxiety and antenatal depression were found to be more prevalent and severe in the first and third trimesters," Lee told Reuters Health. Anxiety and depression levels decreased from early to mid-pregnancy, but increased again late in pregnancy.

However, the data also indicate that new cases of anxiety and depression can emerge at any stage of pregnancy; therefore, doctors need to continually assess the mental health of women throughout the course of pregnancy, Lee said.

Younger age and a history of drinking were strong risk factors for anxiety and depression during pregnancy. As mentioned, women who were anxious or depressed before giving birth were also at significantly increased the risk of suffering from postpartum depression.

Mental health problems during pregnancy are "serious" issues that need addressing, Lee and colleagues conclude, because they are known to have a negative impact on women and their children.