Fetal Taste and Maternal Diet

Babies get plenty of experience with taste before they are born. Flavors, like garlic, change the scent of the amniotic fluid and the flavor peaks around 45 minutes after the mother eats.¹ By the eighth month of pregnancy, babies in the womb are already reacting to the flavors around them — and their faces say it all. In one recent study, mothers were asked to swallow capsules flavored with either carrot or bitter kale. The result? Ultrasound images showed that babies exposed to the sweet carrot flavor made more “laughter-like” facial expressions, while those exposed to kale made more “cry-like” faces.²

But facial expressions aren’t the only clue. The fetus begins swallowing amniotic fluid between 12 and 13 weeks gestation.³ As early as 34 weeks, babies will swallow less amniotic fluid if it tastes bitter,⁴ and more if it tastes sweet.⁵ Thus the fetus is actively tasting and responding to the flavor of the amniotic fluid.

The fetus will swallow less amniotic fluid if it tastes bitter,⁶ and more if it tastes sweet.⁷(Image Credit: Science Source)

Furthermore, by 28 weeks, the fetus can distinguish between different smells in the amniotic fluid.⁸ When researchers presented newborns between one and six days old with unfamiliar odors, the odors activated the same regions of the brain that are active in adults.⁹ The same brain areas are also likely responsible for processing odors a short time before birth.

Together, these findings offer a remarkable insight: even before birth, babies are already reacting to smell and taste molecules that they like and don’t like. Flavor sensations are part of the fetal experience well before the first bite of baby food.

What do babies learn about odors and flavors before they are born?

Researchers have found that babies recognized their own amniotic fluids right after birth. In fact, when researchers brushed amniotic fluid on one breast but not the other, newborns preferred the breast that had been brushed with fluids from their amniotic sac.¹⁰ However, babies lose this preference a few days after birth. When pregnant mothers consumed anise, their babies also recognized the smell of anise on a cotton swab in the first week after birth.¹¹

How long can prenatal taste learning last?

Research shows that prenatal taste learning can last for months. That suggests that what a mother eats during pregnancy can shape the food preferences of her children.

In one experiment, researchers asked pregnant women to drink carrot juice following one of these three protocols:

Drink carrot juice 4 days per week while pregnant, then stop drinking carrot juice altogether. The women drank the juice for 3 weeks starting when they were 33 weeks pregnant (31 weeks after conception).
Avoid carrot juice and carrots while pregnant, then drink carrot juice 4 days per week for the first two months of breastfeeding.
Avoid carrot juice and carrots while pregnant and breastfeeding.

The food that mom eats changes the flavor of the amniotic fluid, giving the fetus experience with his mom's diet long before he is born.

When a woman only drank carrot juice during pregnancy, this allowed researchers to test for the effects of flavored amniotic fluid. When a woman only drank carrot juice after pregnancy, this allowed researchers to test for the effects of flavored breastmilk. Then, more than five months after the babies were born, when they were just starting to eat their first solid foods, the researchers gave the babies two kinds of cereal – carrot-flavored or plain.

Babies who had been exposed to carrot flavors in utero or in the breastmilk made fewer negative facial expressions while they ate the carrot-flavored cereal than when they ate the plain cereal.¹² But babies whose mothers never drank carrot juice showed no preference in cereal. This taste learning is impressive considering that the babies who were exposed to carrot flavors in utero were only exposed 12 times over the course of 3 weeks, and that they had no further exposure to carrot flavors over the next 5 months.

While a healthy maternal diet can influence a baby’s preferences, an unhealthy diet can do so as well. For example, long before a baby is at risk of fetal alcohol syndrome, the taste of alcohol in the amniotic fluid influences the unborn baby’s reaction to the smell of alcohol. In fact, the more frequently a mother drinks alcohol during pregnancy, the more pleasure her one week old baby will display when he smells alcohol.¹³

...the more frequently a mother drinks alcohol during pregnancy, the more pleasure her one week old baby will display when he smells alcohol.¹⁴

In rats, even a single dose of alcohol added to the amniotic fluid on the day that a pup is born made the rats drink more alcohol and display more pleasure for the smell of alcohol eight days later.¹⁵ Finally, multiple epidemiological studies have shown that maternal alcohol consumption changes the ways that her future children consume alcohol as they grow older.¹⁶ So, drinking alcohol during pregnancy may give babies a taste for alcohol.

Eating junk food during pregnancy may also have long term consequences. Research on rats have found that when mothers ate lots of high-fat and high-sugar foods – like chips, doughnuts and processed meats – their offspring had altered brain reward pathways. In other words, compared to rat pups whose mothers ate a healthy diet, the rat pups born to mothers who ate junk food had to eat more sugary, high-fat food to get the same “rush” of dopamine that makes eating junk food so pleasurable.¹⁷ Unsurprisingly, these rat pups also consumed more junk food than pups whose mothers had eaten a healthy diet.¹⁸

It is important to note that the rat mothers ate junk food daily throughout their pregnancies, and the carrot juice study involved consumption of carrot juice four times a week. If the women only drank carrot juice twice a month, would their babies have responded the same way? We do not know. But frequency and dosage matter. So don’t stress that an occasional ice cream sundae will program a baby to love sugary food. Moderation is key.

Newborns can recognize scents from the mother's diet in the first week after birth.¹⁹(Image Credit: Science Source)

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Fetal Taste and Maternal Diet