If
I asked you for the most apparent change in a pregnant woman, you would
probably not answer ‘the brain’. Looking at all the physical changes in
a woman’s body during pregnancy, it is understandable that the brain
seems to be a supporting rather than a main actor in the 9 month-long
play called pregnancy. Here is why – surprise – the brain is important for pregnancy and child birth.
The
pregnant brain needs to coordinate physiological changes that on the
one hand allow the baby to grow and on the other hand prepare the mother
for the challenges of giving birth and motherhood. Female sex steroid
hormones, like estrogens and progesterone are elevated during pregnancy and can act on the brain to induce changes that favor
pregnancy, like increased appetite, a reduced stress response or the
inhibition and accumulation of neuropeptides until they are needed [1].
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| Adapted from http://bit.ly/2dlW1si |
Hungry All the Time?
Growing
new life inside one’s body means that a lot more energy is needed – to
supply the fetus with nutrients and to build up energy reserves that can
be used in the period of lactation after the child is born. Appetite is
usually regulated so that energy intake is in balance with energy
expenditure [2]. To allow for increased food intake, changes in the
brain that suppress the sensation of satiety take place. While satiety is normally signaled by the hormone leptin, the pregnant brain develops a
central resistance to leptin, which ultimately increases appetite and
food intake [2]. So, in a sense, your brain acts like your grandma,
stuffing you with food for the bad times!
YOUR BRAIN MAKES YOU HUNGRY
Stressless Superwomen
Since
exposure of the fetus to high levels of stress hormones increases the
risk for cardiovascular, metabolic and psychiatric diseases in later
life, it is necessary to minimize
the exposure of the fetus to stress [3]. This means that either
everyone has to tip-toe around pregnant women, or we need to change the
mother-to-be’s physiological response to stress. If only it were
possible to reduce the levels of circulating stress hormones! Wait –
that is exactly what’s happening. In pregnancy, changes in the maternal
hypothalamic–pituitary–adrenal (HPA) axis occur which render mommy
hyporesponsive to stressors. This process involves changes in several
HPA components, but also higher brain regions and is reflected by
reduced secretion of adrenocorticotropic hormone following stress [3].
PREGNANCY MAKES YOU (ALMOST) IMMUNE TO STRESS
Just On Time!
A
normal pregnancy is estimated to last around 268 days, and more often
than not, the due date is not too far off from what the gynecologist
predicted. To prevent premature birth, the brain has to coordinate the
availability and action of labor-inducing factors. For example, the
neuropeptide oxytocin stimulates contractions of the uterus during
birth. Throughout pregnancy, the hormonal environment changes in a way
that keeps oxytocin-secreting neurons quiescent, while oxytocin
continues to accumulate and its receptor expression increases [1]. This
accumulation of oxytocin is believed to facilitate synchronized firing
of neurons that then secrete pulses of oxytocin during birth. In
concert, these stimulate contractions of the uterus and ultimately
facilitate childbirth [1].
How to Be a Mommy
Let the brain do the job.
Many mothers-to-be might have wondered at some point if they are
capable of being a mom. Maternal love seems to be somewhat natural and
unconditional everywhere in the world. You might have guessed it
already, it is indeed the usual suspect who pulls the strings for
maternal love: your brain.
After
birth, maternal behavior needs to be initiated to ensure survival of
the newborn. The medial preoptic area (mPOA), which has some control
over the reward circuitry, has a central role in the regulation of
maternal behavior. Priming of the mPOA by the changed endocrine
environment during pregnancy is necessary for the fast initiation of
maternal behavior right after childbirth [3]. During delivery, oxytocin
is released and acts on receptors in the mPOA and other brain regions –
and maternal behavior is induced [3].
Your Kid Lives On In You
During pregnancy, cells from the fetus can cross the placenta and remain in the mother’s body –
sometimes for decades. These cells are mainly found in the bloodstream
during and right after pregnancy, but can be found anywhere in the body
as well. Some studies have even shown a migration of fetal cells to the
maternal brain [4]. Different studies found positive or negative effects
on maternal health, ranging from increased risk for autoimmune disease
[5] to improved wound healing [6].
In
a nutshell, your brain needs to adapt during pregnancy and changes a
lot of processes in the body. Being the perfect host, the brain does
everything in its powers to make pregnancy and being a mother possible.
by Juliane Schiweck, PhD Student AG Eickholt
this article appeared December 2016 in CNS Volume 9, Issue 4, From Cradle to Grave in the Brain
