Toddlers can remember smells from the womb

By Stephen Beech

Toddlers can remember vegetable smells from the womb, according to a new study.

Three-year-olds are less likely to react negatively to the smell of vegetables they were repeatedly exposed to before birth, say scientists.

They believe their findings could help establish healthier eating habits in children.

The Durham University-led research team examined the facial reactions of three-year-olds to the non-bitter smell of carrot or the bitter smell of kale.

The experiment followed two previous studies when the researchers recorded the reactions of the same children to carrot or kale — first before birth using ultrasound, and then in the weeks after birth.

The team found that the three-year-olds whose mothers had taken carrot powder capsules as part of a controlled experiment when pregnant were less likely to show negative facial reactions towards the smell of carrot.

Similarly, those whose mothers had taken kale powder capsules while pregnant reacted less negatively to the smell of kale.

The researchers say their latest findings, published in the journal Developmental Psychobiology, support the argument that exposure to flavors in late pregnancy can result in long-lasting odor or flavor memory in children.

They say the study also suggests that experiencing bitter or non-bitter flavors before birth can shape taste likes or dislikes after being born.

Lead author Nadja Reissland, of Durham University's department of psychology, said: "We first observed these children before they were born, at 32 and 36 weeks gestation, using ultrasound scans and then again at about three weeks of age before observing them once more at age three.

"Each time, we coded their facial expressions when exposed to either the carrot or kale flavor or smell.

"What we see over time is that the children are still more favorable to the vegetables they were exposed to while they were in the womb.

"From this we can suggest that being exposed to a particular flavor in late pregnancy can result in long-lasting flavor or odor memory in children, potentially shaping their food preferences years after birth."

For the latest study, the research team followed 12 three-year-olds who had taken part in the pre-birth and newborn studies.

Each child's mother had taken either carrot or kale capsules while pregnant.

Wet cotton swabs dipped in either carrot or kale powder were held under each child's nose.

Their reaction to the different smells was captured on video. The children did not taste the swabs.

The researchers then analyzed the footage to examine the children's facial reactions — either "laughter face" or "cry face" — and compared those with the reactions seen before birth and when they were newborns.

In the pre-birth study, fetuses exposed to the carrot flavor showed more "laughter-face" responses while those exposed to the kale flavor showed more "cry-face" responses.

When studying the children at three weeks, those whose mothers had taken carrot powder capsules while pregnant were more likely to react favorably to the smell of carrot.

Likewise, babies whose mothers had taken kale powder capsules while pregnant reacted more positively to the smell of kale post-birth.

In the latest study, when looking at the children at age three, the researchers found a "significantly reduced" rate of negative facial expressions in response to the odor the children had been exposed to in the womb.

They say that indicates that the sensory experience of babies in the womb continues to influence how they respond as young children.

Co-author Beyza Ustun-Elayan, of Cambridge University and Radboud University Medical Center in the Netherlands, said: "These findings open up new ways of thinking about early dietary interventions, suggesting that flavors from the maternal diet during pregnancy may quietly shape children's responses to foods years later."

Co-author Jacqueline Blissett, of Aston University, said: "These findings give further support to the use of pre-natal exposure for improving children's acceptance of often disliked vegetables."

Co-author Benoist Schaal, of the French National Centre for Scientific Research (CNRS), added: "This study confirms that human fetuses can sense the flavors of foods that pregnant mothers eat, which might affect what they will like for years after birth.

"Research is needed on other odorants and how they affect the fetus and child."

The researchers say further work would be needed to see if the effect of prenatal exposure on children's facial responses to vegetable odors has a meaningful effect on vegetable consumption.