Epigenetic Risks
Although a person’s DNA code is identical in every cell, differ-
ences in the DNA’s epigenetic state can determine cell and
tissue type. For instance, a liver cell has different epigenetic
markers than a heart cell in the same person.
There is evidence environmental factors can repress or
amplify gene expression by altering a gene’s epigenetic state.
For example, active smoking alters DNA methylation in a
number of genes, including tumour suppressors and genes asso-
ciated with coronary artery disease.
Likewise dietary and lifestyle factors can alter the epigenetic
state in a variety of human tissues, and lead to the unmasking of
disease states that increase the risk of complications during preg-
nancy. Even the sex of the individual adds to the epigenetic web,
with males and females responding differently to such exposures.
We have even found that sex differences startin uteroso that
maternal health, foetal growth and newborn outcomes are
different in women carrying a male or a female foetus.Other Factors
Folic acid supplementation in the month prior to conception
and during the first trimester of pregnancy can prevent neural
tube defects such as spina bifida in babies. We have found that
first trimester folic acid supplementation also protects women
from developing preeclampsia, delivering preterm and having
a small-for-gestational-age baby.
This suggests that folic acid supplementation may be bene-
ficial to the placenta and how the mother adapts to pregnancy,
as well as to the foetus. This has considerable biological plau-sibility, since folate is the pivotal factor in one-carbon metab-
olism, and thereby production of S-adenosyl methionine, the
universal donor of methyl groups in DNA methylation. There-
fore, folic acid supplementation can contribute to the appro-
priate epigenetic state for correct gene expression and healthy
development.
We have also found that women can significantly reduce
their risk of developing pregnancy complications if they eat
three or more serves of fruit and/or one or more serves of green
vegetables each day in the month prior to conception and during
the first trimester. Fruit and vegetables contain folate as well as
other micronutrients and fibre that together may help to
improve the outcome of pregnancy.
Maternal smoking damages the placenta and impairs foetal
growth, and is associated with foetal growth restriction and
preterm birth. Maternal illicit drug use is similarly damaging.
In fact, we have shown that continued use of marijuana, inde-
pendent of cigarette smoking, at 20 weeks gestation is strongly
associated with preterm birth.
Maternal overweight and obesity are increasingly prevalent,
with more than 50% of Australian women commencing their
pregnancy in these categories. A body mass index above 30
indicates obesity and significantly increases the risk for most
pregnancy complications as well as long-term health issues for
offspring. Obese women are more likely to deliver a baby with
birth defects than lean women, and their children are more
likely to be obese and develop type 2 diabetes early in life.Screening for Those at Risk
The screening tools we have developed to predict the risk of
pregnancy complications include many of these factors in
different combinations for each disease. Importantly, they also
point to potential new interventions.
Despite each of us being at genetic risk, our genes are just a
part of the story. Although we cannot change our genomes, we
can change our epigenomes and modify the effects of our genes.
Fortunately, many of the factors that contribute to pregnancy
complications are modifiable.
Ideally, pregnancies should be planned ahead and women
should achieve a normal weight, have a good diet with recom-
mended supplementation of micronutrients, and engage in
moderate exercise both before and during pregnancy. Pre-
conception planning can help to minimise the risks to maternal
and infant health.
One can’t help but think that mum was right when she told
us to eat our fruit and vegetables.
Claire Roberts is a NHMRC Senior Research Fellow who leads the Pregnancy and Birth
Theme at The University of Adelaide, Robinson Research Institute. Tina Bianco-Miotto is a
lecturer at The University of Adelaide’s School of Agriculture, Food and Wine.28 | JAN/FEB 2016
Epigenetics
Epigenetics refers to chemical additions to our genome that
regulate gene expression without changing the underlying DNA
sequence. These epigenetic changes include DNA methylation,
histone modifications and non-coding RNAs.
DNA methylation is the most widely characterised epigenetic
phenomenon. It is the addition of a methyl group (CH 3 ) to a
cytosine base, and is reversible and heritable. DNA methylation
can be affected by what we eat and drink, pollutants in the air
we breathe and the water we drink, drugs we take, smoking, and
potentially even the creams we put on our skin.Obese women are more likely to
deliver a baby with birth defects
than lean women, and their children
are more likely to be obese and
develop type 2 diabetes early in life.