But the same may not hold true for cleft palate, the Norwegian researchers said.
A cleft lip occurs if the tissue that makes up the lip doesn't join completely before birth, leading to an opening in the upper lip. A cleft palate occurs when the tissue at the roof of the mouth doesn't fuse completely during pregnancy.
The researchers found that babies born with cleft lip, with or without cleft palate, had no greater risk for health problems and death than those born without clefts.
But they found that infants born with cleft palate alone had a slightly increased risk of dying early and of having conditions such as intellectual disability, autism and severe learning disabilities.
"These results are relatively good news for parents of children with cleft lip and cleft palate," said lead researcher Dr. Erik Berg, who's with the University of Bergen.
One of the limitations of the study was that the number of people with a cleft palate who died early or had developmental problems was so small that it's impossible to assign the extent of the risk for any one outcome, Berg noted. Only an association was seen between cleft palate and risk of future problems.
He said that because cleft lip is easier to identify with an ultrasound before birth and a cleft palate usually can't be seen before delivery, these "findings could be relevant for future counseling of parents who are concerned about the health of their fetus if a cleft lip is detected during pregnancy."
For the study, Berg and his colleagues collected data on about 1.5 million births in Norway between 1967 and 1992. The study included more than 2,000 babies born with oral clefts who were followed until 2010, when they were between the ages of 18 and 43.
The final analysis included more than 2,300 babies born with clefts and more than 1.4 million infants not born with clefts.
The study findings were published online Sept. 26 in the journal JAMA Pediatrics.
One expert said there can be a lot of variance in how a cleft lip and cleft palate are treated because there are no established standards of care.
"Clefts of the lip and palate occur in one in 700 births," said Dr. Kelly Evans, an acting assistant professor in the department of pediatrics at the University of Washington in Seattle. She co-wrote an editorial that accompanied the study.
Although clefts are common, little research has been done on the best care for children born with clefts and the adults they become, Evans said. "Consequently, health care for those with clefts can look very different from one hospital to another," she said.
"In addition, we know very little about health of adults who were born with a cleft, and this makes it challenging to know if the care that we deliver early is having the best long-term effects," she said.
This study should increase awareness of cleft-related care, Evans said. Health care professionals, researchers, patients and families need to continue to work together to conduct research into the conditions, she added.
"Ultimately, such collaborations will pave the way to ensure that all individuals with clefts have access to optimal treatments to achieve the best outcomes possible throughout childhood and adulthood," Evans said.
Dr. Edward McCabe is chief medical officer for the March of Dimes. He said the study findings "should be reassuring to families in which an ultrasound picks up a cleft lip. It might be concerning to those with a cleft palate."
The causes of clefts aren't known, he said.
It's important to be aware that potential problems may exist and to identify them early so children get the help they need early, he said.
"It doesn't mean that every baby with a cleft palate is going to have problems, but there is an increased risk," McCabe said.
Visit the U.S. Centers for Disease Control and Prevention for more on cleft lip and cleft palate.
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