Beijing – Elevated birth weight has been linked with developing a common heart rhythm disorder atrial fibrillation later in life. Chinese researchers from Zhejiang University, Hangzhou, China said that the risk of atrial fibrillation in adulthood may be higher for large newborns (over 4 kilos or 8 pounds 13 ounces) than those with normal birth weight. The relationship between birth weight and atrial fibrillation is controversial and this study investigated the lifetime causal effect of birth weight on the risk of atrial fibrillation. A naturally randomised controlled trial was conducted by researchers. First, they used data from 321,223 individuals in a genome-wide association study (GWAS) to identify 132 genetic variants associated with birth weight. Next, they identified which of those variants play a role in atrial fibrillation using data from 537,409 participants of the Atrial Fibrillation Consortium (of whom 55,114 had atrial fibrillation and 482,295 did not).