(HealthDay) -- A considerable proportion of women report continuing to drink during pregnancy, but biomarker tests indicate they are drinking at modest levels, according to a study published online April 6 in Alcoholism: Clinical & Experimental Research.

Using the Use Disorders Identification Test (AUDIT), Erika Comasco, Ph.D., from Uppsala University in Sweden, and colleagues collected data on alcohol consumption before and during pregnancy among 2,264 women from a Swedish antenatal clinic. Nicotine use was also assessed. A subsample of women provided serum and blood samples mid-pregnancy to test for specific alcohol biomarkers for excessive drinking.

The researchers found that 89 percent of the women reported regularly consuming alcohol and 49 percent reported occasional or frequent binge drinking before pregnancy. Twelve percent of women continued using alcohol and 5 percent admitted binge drinking during pregnancy. However, all alcohol values were below the reporting limits. Self-reported drinking during pregnancy correlated with a higher pre-pregnancy AUDIT score, nicotine use at the time of the first prenatal visit, older age, and previous legal abortions. Fifteen percent of women reported using nicotine before pregnancy, while 5 percent admitted using nicotine during pregnancy.

"While the AUDIT results suggested that a significant number of continued using alcohol during , implying a risk for fetal disorders, the biomarkers showed negative test values thus indicating only modest levels," the authors write. "The continuation of this study will investigate the development of children exposed to alcohol during fetal life, together with other pre- and postnatal factors, genetic factors, and behavioral characteristics."