Having a child with Down syndrome may come as a surprise, but it’s a good experience, families are reporting in a trio of new surveys.

Researchers surveyed more than 3,000 family members and people with the chromosomal disorder across the country for what’s believed to be one of the largest looks at life with Down syndrome. The findings, which will be published in three articles in the October issue of the American Journal of Medical Genetics, offer a rosy picture.

The vast majority of parents said they have a more positive outlook on life because of their child with Down syndrome. And, nearly 90 percent of siblings indicated that they feel like they are better people because of their brother or sister with the developmental disability.

Nearly all of the survey respondents with Down syndrome said they were happy with their lives, themselves and their appearance. Only 4 percent said they felt sad about their life.

“As international discussion is mounting over the new prenatal tests, family members have now had their say about life with Down syndrome,” said Susan Levine from the disability nonprofit Family Resource Associates, who worked on the study alongside researchers at Children’s Hospital Boston and the Dana-Farber Cancer Institute. “And, more importantly, the people with Down syndrome themselves have clearly stated that they consider their lives valuable.”

Researchers did acknowledge that the survey population could be a slightly biased one since all respondents came from families that are members of nonprofit Down syndrome groups. Nonetheless, they say the findings are valuable since they offer the “largest and most comprehensive portrait of life with Down syndrome to date.”