Pregnancy and the human brain: a window of neuroplasticity

During mammalian pregnancy, the body and brain are exposed to unequaled levels
of sex steroid hormones. In non-human animals, this period is known to involve
substantial, long-lasting alterations in neural architecture. Surprisingly,
very little is known on the effects of pregnancy on the human brain, although
hormone surges on a much smaller scale have been shown to affect brain
morphology. In a previous prospective MRI study, we found extensive and
long-lasting alterations in gray matter volume after pregnancy, which were
primarily located in a network of higher-order association areas subserving
social cognition (Hoekzema et al., 2017). While our previous findings on the
impact of pregnancy on neural gray matter structure point to the existence of a
dramatic pregnancy-related neural plasticity in humans, these insights only
begin to scratch the surface and pave the way for further exploration of this
topic.

Beyond mapping the pregnancy-related neural plasticity in structure and
function, this project is designed to reveal functional and behavioral
implications of the transformations impacting a woman*s brain across this major
transitional stage. The proposed study is designed to reveal a comprehensive
map of the transformations manifesting in a women*s brain across the unique
transition to motherhood, by investigating changes in gray matter anatomy,
structural and functional networks and connectivity and neural activity related
to reward, inhibition and empathy. Furthermore, this study aims to gain key
insights into the neural changes and associated biological factors underlying
specific adaptive and maladaptive changes in maternal functioning.

This topic will be investigated using a prospective within-subjects
case-control setup. Women with the intention to get pregnant in the near future
will participate in an experimental session before trying to achieve this, and,
if successful, will be asked to participate in a pregnancy session during the
third trimester, an early postpartum (as soon as feels good, preferably after 4
weeks) and a late postpartum session (around one year after giving birth).
Participants with no intention to become pregnant within the following year
will be recruited as controls and will also take part in longitudinal
experimental sessions. During the experimental sessions, we will use structural
MRI and Diffusion Tensor Imaging (DTI) to examine brain anatomy. Moreover, the
participants will perform fMRI paradigms targeting the reward circuitry,
inhibition, and empathy as well as a resting state fMRI paradigm. Performance
on a battery of cognitive tests and questionnaire data will also be collected.
In addition, hormone levels, genetic information and inflammation markers will
be determined from saliva, blood, hair, feces, and breastmilk. Except for the
blood samples, all measures are non-invasive.

There are no known risks associated with participating in an MRI study. This is
a noninvasive technique involving no catheterizations or introduction of
exogenous tracers. Numerous children and adults have undergone magnetic
resonance studies without apparent harmful consequences. Some people become
claustrophobic while inside the bore;magnet and in these cases the study will
be terminated immediately at the subject's request. The only absolute
contraindications to MRI studies are the presence of intracranial or
intraocular metal, or a pacemaker. Subjects who may have metallic foreign
bodies in the eyes or head, or have cardiac pacemakers, will be excluded.
Relative contraindications include pregnancy and claustrophobia. The first
acquisition will be planned prior to the participant*s pregnancy, but the
second session involves an MRI acquisition in the third trimester of pregnancy
for those women who can still participate in such a session without
experiencing discomfort (i.e. inability to lie on back or side). Pregnancy is
considered a relative contraindication for MRI exposure. However, in contrast
to early pregnancy, MRI in the third trimester is commonly used for clinical
purposes to examine fetal health. In addition, magnetic resonance imaging in
the third trimester of pregnancy is also increasingly used for scientific
research of healthy fetal development. Moreover, a growing body of research has
examined the short-term and long-term consequences of in utero MRI exposure
during late pregnancy, and these have not observed any effects on child
development or hearing capacity.
Although there is no direct benefit to the participants from this
proposed research, there are greater benefits to society from the potential
knowledge gained from this study. This knowledge is critical to increase our
understanding of the way the human brain is modified during pregnancy, a topic
of wide interest that affects many women. Moreover, this knowledge will pave
the way for elucidating how these changes contribute to the development - and
potential disruptions herein * ofadequate maternal responsiveness, to identify
neural markers that signal a predisposition for peripartum mental disorders and
to evaluate the gestational changes that precede their emergence.