Before science gave us a better understanding of what happens during conception, pregnancy, and birth, there were many old wives’ tales and myths. Most of these tales were trying to make sense of why bad things like birth defects, congenital problems, or stillbirths happened.
One of the earliest beliefs was the theory of maternal impression. This was the idea that if the mother received a bad fright, had some other strong emotion, or saw something horrible, that the experience would impress itself on the baby.
A common version of this belief was that if a baby was born with a cleft lip, it meant that the mother had seen or been startled by the sight of a rabbit or hare. This is why an old name for a cleft lip was “hare lip.” Even if the mother didn’t remember having seen a rabbit, it didn’t matter. The baby had a hare lip and rabbits were not uncommon, so therefore it must have happened. If she hadn’t seen a rabbit, maybe she had been thinking of one or saw one in a dream.
Another version was that a baby born with webbed fingers or toes was caused by the mother seeing a frog or toad or just dreaming or thinking of one.
The concept of maternal impression, which was also called maternal imagination, was based on the idea that women were more strongly affected by their emotions than were men. These emotions were impressed on the infant as it was being formed and marked the baby in some way.
One of the most famous examples of a birth defect being attributed to maternal impression was the Elephant Man, Joseph Merrick (often called John Merrick), who was born in 1962. He started developing growths on his skin and bones that disfigured him. He became so disfigured that he was displayed as a freak at circuses and fairgrounds starting in his late teens. His skin came to look like that of an elephant. His circus employers told the crowds who saw him that his condition was caused because his mother had been knocked down by a circus elephant while she was pregnant with him.
Joseph Merrick’s life has been told in both a play and a movie. Although there have been several ideas on what actually caused his condition, including genetic conditions like neurofibromatosis and Proteus syndrome that cause growths and misshapen bones, it has never been clear exactly what caused his deformities. But it was not caused by maternal impression.
A less well-known case of supposed maternal impression was that of Mary Toft. Toft was a woman who lived in England in the 1700s. Toft said that she had been fascinated by rabbits during a pregnancy which she said caused her to give birth to rabbits. She convinced doctors that she was giving birth to a series of rabbits. Toft finally confessed that the whole thing was a hoax, but the whole incident gave the English medical profession a reputation of being gullible.
In addition to birth defects, other issues with the child could be blamed on maternal impression. If the mother experienced a great sadness during her pregnancy, it would cause the baby to be depressed and sad through their life.
Maternal impression, even though it was a myth and didn’t work, would sometimes be put to use. Pregnant women were sometimes told to think of beautiful things and look at fine art so that they would have a good-looking baby. Some women even used the idea to say that they had seen a picture or dreamed of another man, to explain why the child didn’t look that much like the husband. This excuse may or may not have helped them out of a sticky situation.
As people learned more about how birth defects are caused and how the science of genetics works, the idea of maternal impression was finally recognized as a myth. If a pregnant woman has a bad dream, a passing fancy, sees an animal, or even has a bad fright, it cannot cause a genetic or congenital condition in her baby.
However, there is a concept in genetics called genomic imprinting that actually exists. This is different than maternal impression and is based on new understandings of how genes behave as they are passed from the parents to the child.
Genomic imprinting can influence how some genetic conditions are passed down by parents. Everyone gets half their genes from their mother and half from their father. In genomic imprinting a chemical modification to a DNA sequence changes how the gene works.
With most genes, both versions of a gene are active, but with some only one version is active. In some genetic conditions it is the mother’s version of the gene that is active and with others it is the father’s version of the gene. It is a normal process of genetic inheritance but can have a serious effect with a mutated gene. One example of genomic impression is a gene deletion on part of chromosome 15. If the affected chromosome is imprinted and is inherited from the father, the baby has a condition called Prader-Willi syndrome. If the affected chromosome is imprinted and is inherited from the mother, the baby has a condition called Angelman syndrome.