This is the reason we have सीमन्तोन्नयन Samskar. Once the pregnant lady crosses 6th or 7th month, she becomes अगृहिणी (Temporary relief from household chores) and stops worrying about her duties towards family. No one then gives her any responsibility.
Stress-free life -> Rich Gut bacteria -> Rich brain formation for fetus
Up to सीमन्तोन्नयन Samskar, pregnant mother lives routine life as गृहिणी and she takes care home as head of the family. After सीमन्तोन्नयन samskar, mother becomes अगृहिणी and relieves from daily chores. Generally, this samskar is performed around 6 or 7th month. Last 2-3 months are critical for brain and mind development. This is the time when pregnant mother must live stress-free life.
Stress-free life -> Rich Gut bacteria -> Rich brain formation for fetus
Now slap all dumb driven cattle who debate with you that dharmic rituals are useless.
Becoming अगृहिणी plays CRITICAL role in development of healthy brain and gut for newborn.
Same role is played by breast-feeding.
For reference, read article shared in comment.
Hint: Ideal stress-free life is possible when you live with mother i.e. Pregnant’s mother and/or mother nature. Farm life. Jungle life. Mother’s home.
If you are pregnant or expecting soon, take care! No stress of whatsoever!! Even if a building collapses in front of you, smile! 
🙂 Develop that level of intolerance towards stress. 🙂
Research
Pregnant mother’s stress affects baby’s gut and brain
https://www.newscientist.com/article/dn24586-pregnant-mothers-stress-affects-babys-gut-and-brain/#.Ut_CJeWryc9
Pregnant women may pass on the effects of stress to their fetus by way of bacterial changes in their vagina, suggests a study in mice. It may affect how well their baby’s brain is equipped to deal with stress in adulthood.
The bacteria in our body outnumber our own cells by about 10 to 1, with most of them found in our gut. Over the last few years, it has become clear that the bacterial ecosystem in our body – our microbiome – is essential for developing and maintaining a healthy immune system.
Our gut bugs also help to prevent germs from invading our bodies, and help to absorb nutrients from food.
A baby gets its first major dose of bacteria in life as it passes through its mother’s birth canal. En route, the baby ingests the mother’s vaginal microbes, which begin to colonise the newborn’s gut.
Chris Howerton, then at the University of Pennsylvania in Philadelphia, and his colleagues wanted to know if this initial population of bacteria is important in shaping a baby’s neurological development, and whether that population is influenced by stress during pregnancy.
Stressful pregnancy
The first step was to figure out what features of the mother’s vaginal microbiome might be altered by stress, and then see if any of those changes were transmitted to the offspring’s gut.
To do this, the team exposed 10 pregnant mice to a different psychologically stressful experience, such as exposing them to fox odour, keeping their cages lit at night, or temporarily restraining them every day for what would be the equivalent of the first trimester of their pregnancy. Another 10 pregnant mice were housed normally during the same time.
The team took samples of their vaginal bacteria throughout the pregnancy and again just after the mice had given birth. These samples were genetically sequenced to see what types of bacteria were present.
The microbiomes of the stressed mice were remarkably different to those of the unstressed mice after they had each given birth. There were more types of bacteria present, and the proportion of one common gut bacteria, Lactobacillus, was significantly reduced.
