A urine test for pregnant women may provide a simple way of predicting birth weight, research suggests.
Scientists linked essential nutrients found in urine called branched-chain amino acids (BCAAs) with variations in birth weight.
"We found that a 50 per cent increase in the mother's level of individual BCAAs equated to a 1 to 2.4 per cent increase in birth weight, or 5-11 grams," Dr Muireann Coen, from Imperial College London, said.
Lifestyle comparisons showed that BCAA variability between mothers could be explained by differences in physical activity, vitamin D, coffee consumption and smoking.
This suggested "potential areas of intervention to promote a healthy birth weight," said Dr Coen.
Overall, levels of BCAAs and other chemicals in the urine predicated 12 per cent of birth weight variation.
Scientists collected urine samples and lifestyle data from more than 800 pregnant women aged 28 to 33 in Spain.
The findings are published in the journal BMC Medicine.
