Boys are more demanding than girls before they are born, according to scientists

Date:
April 26, 2022
Source:
St John's College, University of Cambridge
Summary:
Finding out the sex of a baby during pregnancy could lead to better
life chances, a new study has discovered. Male baby pregnancies
are more likely to result in complications, possibly because they
grow faster in the womb and require more nutrients and oxygen than
supplied by the mother through the placenta -- the temporary organ
that attaches to the wall of the uterus during pregnancy to help
the fetus grow and develop.



FULL STORY ========================================================================== Finding out the sex of a baby during pregnancy could lead to better life chances, a new Cambridge study has discovered.


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Male baby pregnancies are more likely to result in complications, possibly because they grow faster in the womb and require more nutrients and
oxygen than supplied by the mother through the placenta -- the temporary
organ that attaches to the wall of the uterus during pregnancy to help
the fetus grow and develop.

Now scientists have discovered the sex of a fetus can affect how well
the placenta actually functions along with factors such as diet-induced maternal obesity and stress, after studying pregnancies in lab mice.

Around one in 10 women are affected by pregnancy disorders, such as
fetal growth restriction and pre-eclampsia -- a life-threatening high
blood pressure condition for both mother and child -- but these can be difficult to predict and treat.

The new research suggests that designing individual treatment plans and encouraging pregnant women to make lifestyle changes based upon the sex
of their unborn babies could have lifelong health benefits for their
children - - and spell the end of the tradition of waiting until the
baby is born to find out whether it is a boy or a girl.

"Often parents don't want to know the baby's sex because they want it
to be a surprise. But actually knowing the sex would help to identify
whether a pregnancy may be at greater risk than another because we
know that some conditions of pregnancy such as pre-eclampsia and fetal
growth restriction can be more prevalent in women that carry male babies
than females," said Dr Amanda Sferruzzi-Perri, a Fellow of St John's
College, who carried out the research with her team from the University
of Cambridge Department of Physiology Development and Neuroscience at
the Centre for Trophoblast Research.



==========================================================================
"We don't quite know 100 per cent why that is but it might be related
to the fact that male babies grow faster within the womb. So it might
be that their demands for nutrients and oxygen supplied from the
mother through the placenta can easily become limited, so the male
baby may not be receiving all that it really wants and needs to grow
to its full capacity. It may be that its resilience against stresses
or poor conditions in pregnancy may be lower than say, for females,
who have got less requirements." Dr Sferruzzi-Perri's research team
has revealed its findings in a paper published in the journal Biology
of Reproduction. A second study written in collaboration with fellow researchers in institutions across the world, which demonstrates how diet-induced maternal obesity changes the structures of the placenta
and affects baby growth, including causing alterations based upon the
fetuses' sex, appears in the journal Acta Physiologica.

Fetal growth depends upon placenta function, which requires energy
from mitochondria -- special compartments in our cells that help turn
the energy taken from food into energy that cells can use as fuel. The researchers have found that in a normal mouse pregnancy, the placenta
responds differently depending on whether it's supporting a female
or male fetus, and functions better with the lightest female fetuses,
than for the heaviest male fetuses.

"The placenta has an amazing skill in changing how it forms and how
it functions," said Dr Sferruzzi-Perri. "This can be seen at multiple
levels from the way in which the cells form in the placenta, it's genes
and proteins, even its mitochondria. These can all change in response to different types of cues, whether it's in a mother that has been eating a sugary, fatty diet, or in a pregnancy where there is rivalry between the siblings when there's more than one baby, but what I think is probably the
most novel aspect is that the way the placenta does adapt seems to depend
on whether the baby's female or male." The studies show the importance
of designing sex-specific therapies for placental insufficiency and fetal growth abnormalities, as well as personalised lifestyle interventions
or therapies for obese pregnant women.



==========================================================================
"The data that we've been generating in the lab has really shown us that
we have to consider the sex of the baby when monitoring a pregnancy,"
said Dr Sferruzzi-Perri. "Therefore maybe treatments should be tailored
based on the sex of the baby." Scientists already know that male and
female risk for diseases such as type two diabetes and cardiovascular
disease is dependent on sex -- males tend to have a higher incidence of
both. "Whether part of this originates from early life exposures is quite
a key area that people like myself and others are really eager to try
and address. One way we are doing this is in mice using environmental conditions, such as diet-induced obesity, which is really widespread
globally, including even in the developing world where urbanisation is
meaning that women are having more access to sugary, fatty diets than
what they have been before," said Dr Sferruzzi-Perri.

In the UK more than half of pregnant women have a body mass index above
the normal healthy range. This is concerning as maternal obesity increases
the risk of pregnancy complications, such as miscarriage, gestational
diabetes, pre- eclampsia and stillbirth. Abnormal birth weights can also
lead to neurodevelopmental issues and immune disorders in childhood,
and to obesity, diabetes and heart disease in adulthood.

"We're now building more and more evidence of what to measure in the
mum in pregnancy like her starting body mass index, her growth, her
gestational weight, but also considering fetal sex. Routinely, clinicians
do consider sex when they're looking at ultrasound images, because sex is
an important determinant of how the fetus is growing. However, we've not
really understood before how that might be determined; how that might
be interacting with the environment of the mother or the way in which
the pregnancy is occurring. So our studies are giving more information
to the clinician to provide more informed decisions about how to manage
that pregnancy.

"It might be that a woman who has a male baby might need to adopt
different lifestyle conditions, than a woman that is carrying a
female." Currently, there are very few ways to treat women with
pregnancy complications other than bed rest, dietary advice, or
delivering the baby early, because of the risks of drugs passing over
the placenta and affecting individual organs of the fetus, which are
very sensitive. Scientists are now trying to think of ways to design
treatments that just go to the placenta.

"These therapies would increase the way in which the placenta functions,
how it develops, even how at the level of its mitochondria, it produces
energy to support fetal growth," said Dr Sferruzzi-Perri. "A lot of this groundwork is reinforcing to us that the placenta is fundamental for
healthy pregnancy outcome, and that fetal sex is important. But by looking
at the different sort of gene, protein and cellular mechanisms, we might identify targets that could be like biomarkers and specifically targeted
in the placenta to improve outcomes for mothers and their babies."

========================================================================== Story Source: Materials provided by
St_John's_College,_University_of_Cambridge. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Esteban Salazar-Petres, Daniela Pereira-Carvalho, Jorge Lopez-Tello,
Amanda Nancy Sferruzzi-Perri. Placental structure, function,
and mitochondrial phenotype relate to fetal size in each fetal
sex in mice.

Biology of Reproduction, 2022; DOI: 10.1093/biolre/ioac056 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/04/220426101645.htm

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