So this isn't necessarily weird science, in that it's not something so odd and out there you'd never see it. It's more that the reason behind the phenomenon is a little funny.
I'm at a time of life where all my friends are getting married. And once they get married, they start spawning. I'm a fan of friend-spawn, and I certainly hope that they all grow up to be adorable awesome little geeks. I will take any kind of geek, science, history, literature, music, theater, I love them all, and I know my amazingly brilliant and talented friends and fellow bloggers will produce some amazingly talented spawn.
Being as I am around such spawning, I've had the opportunity to learn a good bit about babies. And all the charming, cute, sweet, adorable, disgusting, smelling, and gross things that go with them. One of the things I became very quickly interested in was lactation. You know. Boobs and milk. Breast is best. I never realized before that there are lactation consultants. I always thought lactation was one of those things, like sex and giving birth, that people kind of figure out eventually on their own. Survival of the species and all that, you'd figure lactation would be pretty high on the list of things that come naturally.
But in fact, for many women, it doesn't come naturally, and there are certain interventions that you can do to prevent pain and soreness during breastfeeding. But for some women, it seems that all the counseling and intervention in the world isn't working. They have consistent pain while nursing. And now, we know why. The reason? VACUUM BABIES!
McClellan et al. "Infants of mothers with persistant nipple pain exert strong sucking vacuums." Acta Paediatrica, 2008.
It may interest you to know that the sucking from the baby plays a very strong role in lactation in women. And lactation also has a lot to do with dopamine, a molecule of which I am very fond.
Basically, lactation works like this:
1) Baby sucks.
2) Mechanical stimulus from the sucking travels up from the breast to the spinal cord.
3) Neurons in the spinal cord headed to the brain, stimulated by the sucking, INHIBIT dopamine release from the arcuate nucleus of your hypothalamus (hypo=just below thalamus=your thalamus). This is a CRAZY important area of the brain that I think I'll have to blog about sometime.
4) The moratorium on dopamine release removes inhibition on lactotrophs in the pituitary (also a CRAZY important area of the brain). Lacto=milk, troph=producing. These cells are normally under chronic inhibition via dopamine to stop them from stimulating milk, and when dopamine is inhibited, that inhibition is taken away, and milk production ramps up. Relief from chronic inhibition is one of those things which happens a LOT in neuroscience, I know it sounds like a curious twist of thinking, but you get used to it after a while.
5) Side note: suckling and lactation also stimulate the release of oxytocin from the hypothalamus. Oxytocin is a molecule implicated in pair-bonding (especially in voles), and in the formation of emotional bonds in general, and the hypothesis is that oxytocin released during breastfeeding makes bonding between mother and baby more powerful.
6) Side note #2: Stimulation of the spinal cord during breastfeeding also decreases GnRH release from the hypothalamus, which can inhibit the ovarian cycle. BUT. This is not 100% foolproof at all. So it is not a good idea to use lactation as your birth control, or you might end up with siblings extremely close in age.
Ok. That was really just an aside so I could talk about lactation, because I think it's really interesting, especially all the things that can go wrong with it (for example, did you know that if you get REALLY bad whiplash from a car accident, it can shear your pituitary stalk, and lactation will cease? That's really just one of the many life-threatening things that can happen when your pituitary stalk is cut, but it's still an interesting fact). But this paper is actually about step #1, the sucking part.
Many women have pain when nursing. Often these problems are caused by infections, which can occur very commonly in the breast shortly after birth, or improper attachment of the baby, which can usually be helped with the aid of a lactation consultant. But for some women, no amount of help seems to clear up their nipple pain. This is bad, as pain will deacrease your milk production, and can also lead to early weaning, so the baby may not get as much of the beneficial effects of breastfeeding.
So this study looked at a set of women who experienced persistent, bad nipple pain, compared to normal controls, and looked at just how much of a vacuum was taking place when the were nursing. Basically, you can insert a probe in the corner of the baby's mouth, the baby can still form a tight seal, and then you can measure pressure.
What you can see is that mothers who experience a lot of nipple pain have babies which are exerting TWICE the sucking vacuum of controls. Ouchie. The pressure is much worse than that exerted by breast pumps as well, which hovers around negative 200. -200 is the peak of control babysucking power, and the vacuum babies take that and blow it out of the water. Poor moms.
So basically, if you're having persistent nipple pain, this could well be due to your baby exerting strong pressure. Now, they didn't really go into WHY the babies created more negative pressure. Stronger babies? Weaker brest milk production? The mothers with nipple pain produced less breast milk, but this could be an effect of pain, causing less expression, and thus causing the baby to suck harder. Or some women could have less milk expression making the baby suck harder and leading to nipple pain.
Unfortunately, though the mechanism is interesting, it doesn't really give any ideas as to how to help these women. You can't exactly ask the baby politely not to suck so hard. It could be that women with nipple pain like this could have to pump more and nurse less, as none of them experienced pain from the breast pump. It could also be a matter of starting the baby off on pumped milk and switching to breast halfway, so they will be full, and may not suck so hard, and less pain from it might allow more milk expression.
Whatever ends up working, I am all for putting the word "vacuum baby" into common usage among mothers. "Oh, little Edith is wonderful, but she's a real vacuum baby!" I wonder if you listened, would you hear a vacuum sound? Would it be more like "woosh" or
HL McClellan, DT Geddes, JC Kent, CP Garbin, LR Mitoulas, PE Hartmann (2008). Infants of mothers with persistent nipple pain exert strong sucking vacuums Acta Paediatrica, 97 (9), 1205-1209 DOI: 10.1111/j.1651-2227.2008.00882.x