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We all know that smoking during pregnancy is an absolute no-no for baby's health. But a new study is literally putting a face to the statistics.

The new research from Durham University as well as Lancaster University and Nadja Reissland, M.D., includes 4-D ultrasound images of fetuses whose mothers smoke compared against nonsmokers'.

It turned out that the unborn babies of the smoker group touched their faces more, which can indicate delayed development. And they also moved their mouths more, which is an action that would be expected to decline during normal development, according to the authors.

And as the pregnancies went on, the differences between the two groups became even more pronounced.

Basically, the scans appear to show unborn babies wincing when their moms go for cigarettes—and it's heartbreaking.

However, the good news is that the babies in the study, which was published in the journal Acta Paediatrica, were all eventually born healthy.

The study's authors hope to use the images as an educational tool for mothers-to-be in the future, who might be more inclined to stop smoking after seeing the scans.

Related: 10 Bad Habits to Kick Before Getting Pregnant

Co-author Brian Francis wrote, "Technology means we can now see what was previously hidden, revealing how smoking affects the development of the fetus in ways we did not realize. This is yet further evidence of the negative effects of smoking in pregnancy."

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Alesandra Dubin is a new twin mom. She's also a Los Angeles-based writer and the founder of home and travel blog Homebody in Motion. Follow her on Facebook, Instagram, Google+ and Twitter.

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