Children whose mothers smoked while pregnant still carry molecular evidence in their blood at least to age 5, new research shows.

The findings offer strong evidence that environmental exposures that go as far back as the womb remain in the body and may affect a person’s health for years after birth.

With further research, it may be possible to detect less-evident fetal exposures, including to chemicals in plastics, undetected infections, or contaminants in drinking water.

Ultimately, the hope would be to link these exposures to chronic diseases such as obesity or heart disease to better understand how diseases develop and possibly help prevent them.


Says study leader M. Daniele Fallin, professor and chair of mental health at Johns Hopkins University’s Bloomberg School of Public Health:

“Smoking is one thing. But if this turns out to be possible for other kinds of exposures, this could be a paradigm shift.

We have long known that the body is an accumulator of past exposures—evidence of lead exposure lives on in our bones, for example. But we did not know that something as easy to collect as blood could contain evidence of exposures not only during your life but prenatally. That’s what makes this so compelling.

If you have a blood sample, you may be able to ask research questions that you could never ask before.”

The new study, published online in the journal Environmental Research, involved epigenetics, the study of molecules that regulate which genes are turned on and off at various times and in various parts of the body.

Two years ago, other researchers looked at newborns’ cord blood and found that the amount of an epigenetic mark, known as DNA methylation, at 26 locations on the genome was correlated with whether that baby’s mother had smoked during pregnancy.

Secondhand Smoke Exposure?

Fallin and her colleagues took the experiment a step further. They tested the blood of 531 preschoolers from six US sites and also spoke to the children’s mothers about whether they had smoked while pregnant.

They again analyzed methylation patterns at the same 26 locations in the genome and found that 81 percent of the time their test accurately predicted prenatal smoking exposure. It had not been previously known whether this epigenetic signature would still be around as many as five years later, but the scientists found that the children’s blood still contained this molecular memory.

It is possible that the signature is also related to exposure to secondhand smoke after birth, but that would not account for all of it since at birth—before they could be exposed to secondhand smoke—those whose mothers smoked while pregnant already had the signature.

Fallin says she hopes this area of research has broader reach. It is relatively easy to determine if someone was exposed to cigarette smoking in the womb.

You simply ask the mother or someone else whether the mother smoked while pregnant. But exposures to other toxins are more difficult to tease out. For many, the mother may not know if she was exposed.

“If epigenetic signatures can be found for other environmental exposures, these could provide clues to how certain prenatal exposures affect health … potentially decades into life,”

says coauthor Christine Ladd-Acosta, assistant professor of epidemiology.

Fallin, who also directs the school’s Wendy Klag Center for Autism and Developmental Disabilities, says she hopes to determine if in utero exposures contribute to the development of autism. It remains unclear whether these epigenetic biomarkers are a direct cause of chronic diseases later in life or what else they may indicate.

M. Daniele Fallin, et al. Presence of an epigenetic signature of prenatal cigarette smoke exposure in childhood Environmental Research Volume 144, Part A, January 2016, Pages 139–148

For future updates, subscribe via Newsletter here or Twitter