Babies with cystic fibrosis (CF) are more likely to be born preterm — less than 37 weeks of pregnancy — and have significantly lower birth weight, according to a large study from Denmark and Wales.
The study “Impact of cystic fibrosis on birthweight: a population based study of children in Denmark and Wales” was published in the journal Thorax.
CF can cause a nutrition deficit due to malabsorption of food, which results in poor growth during infancy and childhood. However, the effect of CF on intrauterine (in the uterus) growth is unclear.
Researchers from Wales and Denmark collected data from their respective national registries about children born with CF to analyze the effect of the disease and gestational age (a parameter indicating at what stage during pregnancy the child was born) on their birth weight.
A total of 597 children with CF and 1,736,186 healthy children identified from the Danish Medical Birth Register, which monitors the health of pregnant women and their children in Denmark, were included in the study. In Wales, a total of 255 children with CF and 442,409 healthy children were included. The Welsh used the Secure Anonymised Information Linkage databank to access information about these children.
All children were singleton births, meaning they were not twins, triplets, etc.
Overall, results showed that more CF children were born with low birthweight (less than 2.5 kg, or 5.5 pounds) than healthy children in both country populations. Among the Danish children, 11.9% of CF children had low birthweight compared with 4.2% of the healthy children. Similarly, in the Welsh population, 11% of CF children were born with low birthweight compared with 5.4% of the healthy children.
CF children in the Danish and Welsh population weighed 178.8 grams (6.3 ounces) and 210.08 grams less (7.4 ounces), respectively, compared with their healthy counterparts.
Also, more CF children were born preterm than healthy children in both the Danish and Welsh populations. Of the CF children in the Danish group, 12.7% were born preterm compared to 5% in the healthy group. On average, they were born about three days earlier than healthy children.
Among the Welsh children, 9.4% of CF children and only 5.8% of non-CF children were born preterm. They were delivered about four days earlier than non-CF-children.
Researchers found that 35% and 39% of low birth rates in CF children from Denmark and Wales, respectively, were due to their lower gestational age (preterm).
Results also showed that factors like a lower socioeconomic status of the mother and smoking history before pregnancy were associated with lower birth weight and gestational age of the children, irrespective of the CF status of the child.
“In a whole population linkage study in Wales and Denmark, we showed that babies coded as having CF are born on average about 200 g lighter than babies with no CF,” the researchers wrote.
“Babies with CF are born on average about half a week earlier, but this only accounts for around 40% of the total effect of CF on birth weight, suggesting a significant direct biological impact of CF on intrauterine growth,” they added.
The researchers suggested that CF has a significant negative impact on intrauterine growth, which leads, in part, to lower birth weights.
“Birth weight and gestational age are not currently collected in most CF registry datasets, including the U.K., the U.S., and Danish databases. Based on our study results, we recommend the addition of birth weight to the list of variables in CF registries” the team concluded.