Even at the youngest, conception, babies don't need to understand language since they can remotely feel the emotions of those around them and it may influence what they turn out to be.
My second aunt had a miscarriage. She said that when she knew she was carrying she said that she thought that maybe she should give the baby to her brother's family who was childless, her husband scolded her saying "what do you think our baby is? A puppy to be given away?!". It was meant as a joke but the baby must've felt unwanted so hence the miscarriage. Another time when my mother brought over her friend, I listened to the story of how her eldest child was different from other children. He had the face and the impression of an older person, he would scold other children for playing at slides, swings and other such things recklessly. When his mother was pregnant with him they hardly had money. When she felt contractions signaling she was about to give birth, she found out the money for it would not come for a few days, so she told her baby in the womb that "if he could will he wait for the money to come?". Immediately thereafter the contractions stopped until she had the money. Another time she ran out of milk for the baby after he was born. He was crying and she apologized saying if he could wait for awhile while she looked for a way to acquire some money for it, and he stopped crying. Later on though, she and her husband were living well and then she was pregnant with her next child. This child had no restrictions whatsoever. Later on the results could be seen, the eldest was quite reserved while the second child was as just as any child should be.
Some have opposite effects. I friend of my acquaintance was going to have a second child but didn't want it. Instead of having to spend for abortion she thought she could miscarry it by doing heavy work and jumping up and down. Needless to say the baby was stubborn and was born. The child has allergies, when you scratched or slapped her skin it immediately inflamed, the effect of the mother's attempt. But the child grew up proving her worth by excelling in her studies and becoming a renowned violinist in her area. Seeing this from her daughter, she regrets what she had done and silently begs her daughters forgiveness.