Light drinking during pregnancy was not associated with development problems for children – at least up to the age of 7, researchers reported.
If anything, children of mothers who drank lightly had slightly better outcomes than kids whose moms did not drink at all during pregnancy, according to Yvonne Kelly, PhD, of University College London, and colleagues.
But the differences were "modest" and only a few reached statistical significance, Kelly and colleagues reported online in BJOG.
The bottom line is that "there appears to be no increased risk of negative impacts of light drinking in pregnancy on behavioral or cognitive development in 7-year-old children," Kelly said in a statement.
But she cautioned that the children need to be followed for even longer to see if effects might appear later in life.
Heavy alcohol use during pregnancy has been associated with health and developmental problems in children, but the effects of low consumption remain unclear, the researchers noted.
To help fill the gap, Kelly and colleagues analyzed outcomes from some of the 10,534 7-year-olds whose mothers enrolled in the Millennium Cohort Study, a nationally representative longitudinal study of infants born in the U.K. between September 2000 and January 2002.
The study involved home visits, with questionnaires and a battery of cognitive tests, when the children were 9 months, 3, 5, and 7. As well, the children's teachers were surveyed by postal questionnaire.
In response to questions about alcohol use during the first study visit, 12.7% of the mothers said they were teetotalers, 57.1% said they did not drink during pregnancy but did so later in the child's life, 23.1% were "light" drinkers during pregnancy, and 7.2% drank more heavily during pregnancy.
"Light" drinking was defined as no more than 2 units of alcohol a week, where a unit was half a pint of beer, a glass of wine, or a standard measure of spirits.
Kelly and colleagues used propensity matching to define two cohorts of mothers that were similar but for drinking during pregnancy – the light drinkers and those who stopped during the pregnancy. Teetotalers and heavier drinkers were excluded.
To analyze behavioral difficulties in the children, parents and teachers were asked to complete the validated Strengths and Difficulties Questionnaire. As well, the researchers tested the children's reading, math, and spatial skills.
For behavioral difficulties, they estimated percentage differences in the standard deviation score, which ranged without adjustment from 2% to 14% favoring the children of light-drinking mothers.
After adjustment, both by ordinary least squares regression and by propensity score matching, the differences were attenuated and lost statistical significance, except for difficulties among boys, as rated by their teachers.
In that case, the unadjusted difference – favoring the children of light drinkers -- was 13.9% of a standard deviation, which fell to 9.6% in the regression analysis and to 10.8% in the propensity matching analysis.
Similarly, in an unadjusted analysis, the cognitive testing showed children born to light drinkers had more favorable scores in reading, math, and spatial skills by between 12% and 21% of a standard deviation.
Adjustment weakened the differences, but boys remained significantly better in reading and spatial skills in both the regression and propensity matching analyses.
Girls of light-drinking mothers remained significantly better at spatial skills in the regression analysis, the researchers reported.
Kelly and colleagues cautioned that information on drinking during pregnancy was collected 9 months after the fact, raising the possibility of recall bias.
Moreover, they noted, they had no data on the timing of drinking during pregnancy, so patterns of reported alcohol use remain unclear.
The study had support from the Economic and Social Research Council.
The journal said the authors made no financial disclosures.
- Reviewed by Zalman S. Agus, MD Emeritus Professor, Perelman School of Medicine at the University of Pennsylvania and Dorothy Caputo, MA, BSN, RN, Nurse Planner