Babies with genetic conditions

Can my baby breastfeed with a genetic problem?

Breastfeeding and breast milk may benefit some babies with a genetic condition. For example, babies with cystic fibrosis who are breastfed grow as well as those who are infant formula-fed and have better lung function. Some genetic conditions make it difficult or impossible to breastfeed. Babies with galactosemia can't break down one of the components in milk sugar. Babies with phenylketonuria may need a special infant formula that is low in phenylalanine, although studies show some can safely breastfeed without infant formula. Babies with Down syndrome may have difficulty breastfeeding because of a large tongue, weak facial muscles, or heart abnormalities. They may benefit from extra support at the breast.

A) Genetic illness

A few babies are born with genetic illnesses. Some of these babies have no problem digesting breast milk but others are unable to break down certain breast milk parts (Huner 2005; Pinchler 2017). The recommendation to give breast milk or not depends on the nature of the illness.

Please discuss your specific case with your health-care providers.

B) Galactosemia

Breast milk contains a lot of milk sugar (lactose), which is a double sugar composed of glucose and galactose. Babies with galactosemia have gene defects that leave them unable to make an enzyme needed to break down galactose. It then builds up in the blood and becomes toxic. Galactosemia is diagnosed by blood and urine tests. Some countries routinely test newborns using blood taken from a heel prick.

Babies with galactosemia and receive lactose may:

  • Be irritable or sleepy.
  • Gain poorly.
  • Have jaundice.
  • Vomit and have diarrhea.
  • Have cataracts.
  • Have liver disease.
  • Have an increased risk of infection.
  • Have swelling of the brain and convulsions.

Babies with galactosemia should not breastfeed. They are generally given soy-based infant formula and need to be on a very low-lactose diet for their entire lives (Coelho 2017).

C) Phenylketonuria

Phenylketonuria (PKU) is a condition that makes a person unable to process phenylalanine, an amino acid used to make protein. Doctors can measure the level of phenylalanine using blood tests. Some countries routinely test newborns using blood taken from a heel prick.

High levels of phenylalanine can cause significant injury to the baby including:

  • Intellectual disability
  • Seizures
  • Behavioural problems
  • Small heads and poor brain development

Treatment of PKU includes avoiding foods that are high in phenylalanine and using food supplements that are low in phenylalanine. For babies, there are special infant formulas that are low in phenylalanine.

Recommendations vary on allowing these babies to receive breast milk (Banta-Wright 2014; Kose 2018; Pinto 2018) and there are different degrees of PKU severity.

D) Congenital lactase deficiency

A very small number of babies do not make the lactase enzyme needed break down milk sugar (lactose). This kind of lactase deficiency is called congenital, which means the baby was born with it.

Congenital lactase deficiency is a genetic condition that is most common in babies whose families are from Finland, where it affects 1 in 60,000 babies (Kuokkanen 2006; Torniainen 2009; Wanes 2019). 

If these babies are given lactose through breast milk or regular infant formula, they will have watery diarrhea within a few days after starting to breastfeed, dehydration, and weight loss. They will never be able to digest lactose and require a life-long lactose-free diet. They cannot tolerate breast milk. 

E) Down syndrome (Trisomy 21)

Babies with Down syndrome often have difficulty breastfeeding and need extra support, review, and monitoring (Magenis 2020). Challenges include:

  • A large tongue, causing difficulty latching.
  • Weak facial muscles, limiting mouth vacuum strength (Coentro 2020).
  • Other medical problems such as abnormalities of the mouth, swallowing tube, gut, and the heart (Ravel 2019).

These babies benefit from extra support at the breast. Using the dancer hand position can stabilize the baby’s cheeks. Other babies may not be able to latch or breastfeed effectively. Some can learn to breastfeed after a few months.

F) Cystic fibrosis

Babies who are born with cystic fibrosis are at risk of poor nutrition and slow growth and should be closely monitored. Babies with cystic fibrosis who are breastfed (Colombo 2021; Munck 2018):

  • Grow as well as those who are infant formula-fed.
  • Have better lung function than those who are infant formula-fed.
  • Have fewer lung infections caused by the bacterium Pseudomonas aeruginosa.

G) Glucose-6-phosphate dehydrogenase (G6PD) deficiency

Glucose-6-phosphate dehydrogenase (G6PD) is an enzyme that helps red blood cells work. Some individuals have a genetic disorder that results in them not having enough of this enzyme (G6PD deficiency). It is the most prevalent enzyme deficiency in the world.

Mothers of babies with G6PD deficiency should avoid quinine-containing medication and drinks. 


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