Maternal hormone shuts down baby's brain cells during birth

By Ed Yong | October 7, 2008 10:00 am

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Blogging on Peer-Reviewed Research
It is the instinct of every mother to protect their children as they grow up, shielding them from the dangers of the outside world. Right from birth, life can be a difficult experience. Within a few hours, the child is sent from a safe, warm, constantly-nourished cocoon into a bright, noisy and threatening world. This stressful transition poses a serious threat to the newborn’s vulnerable and still-developing mind. But new research has shown that even in these first vital hours, mothers are already inadvertently protecting their children – by shutting down their brain cells.

800px-humannewborn.jpgIn foetuses and new-born mammals, brain activity depends on a vital molecule called gamma-aminobutyric acid, known by the friendlier name of GABA. GABA is a neurotransmitter, a chemical that sends messages between nerve cells, and in young mammals, its message almost always says “Fire.

But Roman Tyzio and colleagues from the Mediterranean University, Marseilles, found that in the brains of baby rats, the message changes just before delivery. For a brief time window, rather than stimulating brain activity, GABA puts a finger to its lips and silences nerve cells instead. During this time, Tyzio saw that the number of cells affected by GABA plummeted to negligible levels.

gfpneuron.jpgHis group found that this chemical volte face is triggered by the mother, through an all-important, multi-purpose hormone called oxytocin. Oxytocin is another neurotransmitter, and one that is almost synonymous with social relationships. It has been linked to sexual arousal, feelings of trust, love and monogamy. During childbirth, massive amounts of oxytocin are released by the mother and can reach the foetus via the placenta.

Artificially adding oxytocin to the brain tissue of foetal rats caused cells to ignore GABA just as they do before delivery. And giving expectant mothers atosiban, an anti-oxytocin chemical, stopped this from happening. It seems that oxytocin’s long list of abilities now includes temporarily shutting down an infant’s nervous system during birth.

Many mothers might dream of doing the same later on in their child’s life but at this crucial juncture, it protects them from the dangers of oxygen deprivation. A lack of oxygen during birth is the number one cause of death or brain damage in newborns. But because oxytocin silences a baby’s brain cells, it greatly reduces their energy needs and their dependency on oxygen.

Tyzio found that the brain cells of baby rats survived without oxygen for an hour if they were delivered naturally. But if mothers were given atosiban, the brain cells of their babies died within 45 minutes. Other studies in sheep have found that the massive flush of oxytocin during childbirth is crucial if mothers are to form stable emotional ties to their babies. Now, thanks to Tyzio’s team, we know that oxytocin might also be important for the baby’s mental development.

These findings have important implications for human mothers too. The oxytocin spike relies on the baby pressing against the cervix during birth. Those delivered through caesarean sections may miss out on the hormone and all its benefits. Caesarean sections are becoming increasingly popular, mainly as an elective procedure rather than an emergency one. Studies like this could give women who opt for these operations pause for thought.

Reference:  R. Tyzio, R. Cossart, I. Khalilov, M. Minlebaev, C. A. Hubner, A. Represa, Y. Ben-Ari, R. Khazipov (2006). Maternal Oxytocin Triggers a Transient Inhibitory Switch in GABA Signaling in the Fetal Brain During Delivery Science, 314 (5806), 1788-1792 DOI: 10.1126/science.1133212

Comments (5)

  1. Interesting post! I need to comment on one sentence though: “Caesarean sections are becoming increasingly popular, mainly as an elective procedure rather than an emergency one. Studies like this could give women who opt for these operations pause for thought.” Women who undergo “elective” sections not necessarily had a choice between vaginal birth and Caesarean birth. They’re just called elective because they can be planned in advance. I had two “elective” sections because otherwise my babies would have been at risk of dying during delivery. There are quite a few conditions for which C/S are indicated, and the overall proportion of C/S births, even with optimal support for vaginal delivery, is 5-10%.
    So what we really should conclude from this is that post C/S, women and babies may need better post natal support to facilitate bonding and help stimulate baby. It would also be interesting to see how large the effect size of the mental health effect is. I know that such an effect has been found for breast feeding, too, but it’s relatively small, and there are a lot of other factors that come into the mix.

  2. Having been one of the grandmas present when an emergency c-section was required, I’m all for the planned ones, or at least doing it a little quicker after it’s decided it has to be done.
    Not only did the heartbeat of the little one go away, but the mother lost so much blood by “almost” going through vaginal delivery and then a c-section that she was terribly anemic. Then add a second epidural for the section because the first one for the labor is “hours” old and you have another problem.
    If only everything were so black and white.
    Believe me, my daughter is planning her next delivery as a c-section without having to go through the “emergency” part of it.

  3. I’m sorry, but I’ve got to call you out on the last sentance as well :) my mum was knocked out half way through delivery for a cesarian (after it bacame obvious that I wasn’t coming out the normal way) and I didn’t see her for the first twelve hours of my life. My relationship with her is wonderful; better than hers with her mum, and she had a natural birth.
    Also, that’s a bit of a dangerous sentance to be throwing around. Suggesting the cesarian some how might make the mother less close to her child might make some woman in situations where birth is becoming unsafe to try to desperately hang onto a natural childbirth under the mistaken impression that if they don’t. It also has the potential to make ‘opt-in’ mothers feel guilty. Going through a tough time with a teenage daughter might make them think “oh this must be because I selfishly opted to be knocked out throughout the whole thing”.
    Very interesting post though, as always.

  4. Jon Anderson

    Thanks for this information. One very minor quibble – my sheep did not experience “childbirth”, they lambed. From past experiences raising hogs, I know that injections of pitocin can bring on delivery in a slow sow – and was used successfully when the sow refused to accept the piglets.

  5. Frances L. Mayes

    The c-section rate in Scotland may be 5-10%, but in the US it is over 30% and climbing. Doctors opt for C-sections because they are less likely to be sued (he did everything he could) and moms because they are convinced that labor and birth are inevitably painful and unpredictable. Babies are sometimes delivered prematurely because moms dates were not accurate. The risks of C-birth are much higher than vaginal birth.

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