Talking to your baby is essential for their development
The National Literacy Trust said it was surprised to learn that 19% of parents-to-be believe speaking to their child before the age of three months was not necessary or were unsure when to start communicating with them.
The trust said starting to talk to babies in the womb and in the early days of their lives was a good way of helping them get the best possible start in developing their language skills and is an early form of English tuition.
One in 20 parents surveyed planned to leave communicating with their child even longer, and thought it would only be necessary when they got to six months or older.
The latest findings, published to coincide with the launch of the trust's Talk to Your Baby campaign, are part of wider research commissioned to mark the National Year of Communication.
The survey, which questioned around 3,000 parents and parents-to-be, found more than a third of expectant parents (38%) and a similar proportion of parents (37%) were unaware of any benefit in talking to their baby while it is still in the womb.
Some 5% of expectant parents thought a child's speech and language skills "happen naturally", and they have no role to play in helping them develop, but the reality is parents have a massive role to play in early English tuition for children.
National Literacy Trust director Jonathan Douglas said: "Few moments in life are more magical than the first time you hear your baby talk. It's the start of a lifelong conversation.
"But we want parents to understand that talking with your baby doesn't have to involve words. Your baby cooing, babbling or even simply holding your gaze is a way of them communicating.
"The Talk to Your Baby campaign aims to help parents understand that by responding positively to their baby's earliest attempts at communication and taking every opportunity to talk with their baby they will build their child's confidence and help them develop language skills that will be with them for life."