Can ‘full term’ babies born before 40 weeks find it harder to breastfeed?

stork-carrying-babyThe fact that premature, or preterm, babies can experience difficulties breastfeeding is well documented. Neurological immaturity, poor muscle tone and underdeveloped reflexes can all affect the ability to perform suckling movements, so babies born early generally don’t find it as easy to feed directly from the breast as babies born at full term1. The length of time that constitutes ‘full term’ is slightly hazy, however. Although the average pregnancy lasts 40 weeks, it is usually from 37 weeks gestation that babies are regarded as being sufficiently mature to qualify as term. There is some evidence, however, that babies born after 37 weeks, but before 40, may not always be as well developed as those born later, and a large study in Australia suggests that this could potentially make it more difficult for them to breastfeed2.

The study looked at the impact that length of gestation had on breastfeeding rates in a sample of 3600 children born over the period of a year. Babies were divided into three groups: those born before 37 weeks (preterm); those born at 37-39 weeks (early full term); and those born at 40 weeks and over (late full term). Preterm babies were the least likely to be breastfed – only 88% of mothers in this group initiated breastfeeding (compared to 92% in the early full term group and 94% in the late full term group), but this could have been due to social factors such as the age and level of education. Although there appeared to be a small difference in the initial breastfeeding rates of the early and late full term babies, it was not statistically significant. 6 months later, however, when breastfeeding status was next documented, the gap had widened to a significant level.

Pre-term babies were still the least likely to be breastfed – only 41% were still being nursed at this point, compared to 61% of the late full term babies. 55% of the early full term babies were still breastfed at 6 months – more than in the preterm group, but significantly fewer than in the older full term group. The fact that there was a difference between the full term groups at 6 months, but not initially, is important as it indicates that early full term babies may be at greater risk of breastfeeding failure: mothers of the younger babies were as likely to start breastfeeding, but they were more likely to stop before their babies reached 6 months. This difference can’t be explained by the other factors recorded in the study, and the underlying reasons for it aren’t clear, but the authors suggest that it may have arisen due to subtle immaturity, such as underdeveloped mouth muscles, that can affect babies born before 40 weeks, even when they have passed the 37 week milestone.

If your baby is born slightly early, the chances are, of course, that she won’t have any major problems breastfeeding. In the study reported above, the majority of babies born after 36 weeks were still breastfeeding 6 months later, so the prognosis is good. It’s still worth noting that a gestation period under 40 weeks might decrease the chance of a mother continuing to breastfeed, however, so any difficulties that do arise can be picked up and addressed before it’s too late. With a little patience and practice even very preterm babies can adjust to breastfeeding as they get older1, so dealing with problems caused by mild immaturity is comparatively straightforward. The key is being aware they may occur: recognizing that for some babies born between 37 and 39 weeks breastfeeding may be difficult for a short time – and providing the right support to mothers through this period – would help ensure that many more babies born slightly early are able to successfully achieve exclusive breastfeeding.

  1. Infant, 2005 July; 1(4):111-115.
  2. Arch Dis Child Fetal Neonatal Ed. 2008 Nov;93(6):F448-50.
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