I’ve been asked a few times whether the lactic acid released during massage is safe when you’re pregnant. Does it reach the unborn baby and what are the effects? Usually it’s concerned partners rather than women themselves that ask the question. Just recently I’ve been massaging a pregnant obstetrician who is a lecturer for Auckland University and specialises in the placenta. I asked her about lactic acid and so she did some reading and discovered the following in the literature…
A little follow on from your lactic acid question last night…
From what I can tell from the literature, there is nothing to worry about with lactic acid release from massage affecting the baby for two reasons
1) A number of papers in the sports science literature in recent years has shown that even deep tissue massage doesn’t actually result in significantly increased lactic acid release from muscle, meaning there isn’t more lactic acid in the blood stream following a massage in the first place. This isn’t a bad thing – lactic acid is increasingly being seen as a ‘useful’ molecule rather than just a toxic by-product.
2) Lactic acid can not only cross the placenta, but under normal conditions the placenta actually converts about a third of the glucose it takes up to lactic acid, which acts as a major source of metabolic fuel for growth. The placenta will also increase its production of lactic acid to help fuel metabolism when there isn’t enough oxygen available, just like muscles do. While this means that in this situation the pH of the fetal circulation is lowered slightly (more acidic), which isn’t ideal for organ development over the long term, it does help ensure that fetal metabolism (and growth) is able to continue – so it’s kind of the baby making the best of a bad situation if it can’t get enough oxygen. So circulation of blood to the uterus and the amount of oxygen the placenta receives is going to have far more of an effect on lactic acid than massage ever would, and unless the mother is doing really hard out anaerobic exercise (like hill sprints), or living in the Himalayas at high altitude, this is actually largely beyond her control, and more about how well the placenta has done its job to adapt the uterine circulation to achieve this!
So, I’d say the relaxing benefits of massage and generally easing aches and pains are a big plus in pregnancy (stress can negatively affect the immune system, which plays a really important role in tolerating the placenta and baby which are kind of like organ transplants that the immune system should recognise as being foreign, but doesn’t – a whole other fascinating story) and tell people to not worry about the lactic acid!
Dr Jo James
Department of Obstetrics and Gynecology
FMHS, University of Auckland
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