What is the normal ratio for Down syndrome births in women over 35?

The normal ratio for Down syndrome births in women over 35 is approximately 1 in 385. This means that for every 385 women over the age of 35 who give birth, one baby will be born with Down syndrome. However, it's important to note that this ratio is an average and can vary depending on individual factors and circumstances. Advanced maternal age is one of the most significant risk factors for Down syndrome, and the risk increases with advancing age.