Can stress affect the let-down reflex?

cartoon of person with numbers flying round their headOne piece of advice you might have heard from midwives (and well-meaning friends and family), is to make sure you breastfeed in quiet and relaxing surroundings. Given the choice, this is probably what you’d opt for (who wants to feed in noisy and distracting surroundings?), but could it actually cause a problem if you’re not able to do this?

Well, there’s a possibility it could. For some time, medical evidence has existed that indicates temporary stress or distraction can interfere with the let-down, or milk ejection reflex, meaning your baby has to wait longer for milk to start flowing freely.

Normally, cues that indicate your milk will soon be required (such as your baby crying before a feed, or suckling at the start of one1) trigger the release of the hormone oxytocin, which enters the bloodstream in ‘pulses’ a few minutes apart, forcing milk to flow from the ducts and out of the nipple (see ‘Breastfeeding and Human Lactation’ by Jan Riordan for a full description of this somewhat complicated process.)

In 1948, an experiment conducted with a single breastfeeding woman indicated that distractions can inhibit the release of oxytocin, delaying the start of milk ejection2. This effect was confirmed in a more recent study, which monitored the oxytocin levels in the blood of three groups of breastfeeding mothers who had given birth five days previously3. The first group was asked to perform difficult verbal arithmetic problems whilst nursing their babies (the stress condition), the second was subjected to the noise of a building site through earphones (the noise condition) and the third breastfed without these distractions (the control group).

Oxytocin release occurred significantly later and less frequently in the noise and arithmetic groups than it did in the control group, indicating that these temporary stressors impaired the mothers’ let-down reflexes. The amount of milk the babies consumed (measured by weighing them before and after the feed) did not differ between the groups, however, so although stress affected the frequency of let-down, it did not appear to prevent babies from consuming an adequate amount of milk.

These results demonstrate that mild temporary stress, such as trying to perform difficult arithmetic problems (five days after giving birth!) or being exposed to the noise of construction work can delay the let-down reflex, both at the start of a feed, and throughout its duration. This may explain why in situations where you feel under pressure or distracted (for me, this certainly applies to feeding in public), it feels like your milk takes forever to appear – not great when you’re trying to deal with an angry baby. Fortunately, this problem doesn’t appear to affect the amount of milk your baby consumes overall, so it isn’t necessarily anything to worry about (this would probably only make it worse, after all…) Nevertheless, it is an irritation that both you and your baby would probably prefer to avoid, and therefore the perfect excuse to insist that your surroundings whilst breastfeeding are as chilled out as possible.

  1. Br Med J (Clin Res Ed). 1983 Jan 22;286(6361):257-9.
  2. J Pediatr. 1948 Dec;33(6):698-704.
  3. Obstet Gynecol. 1994 Aug;84(2):259-62