At the time of the first birth, the mother is young (generally speaking, except special), with good physical quality, adequate supply of nutrients in the body, and good detoxification function such as maternal blood circulation, which can better bring out the waste toxins from the placenta, so generally speaking, the first-born child can be in better health.
However, there are gains and losses. At the time of primiparity, expectant mothers generally have no experience in childbirth and childbirth, and can't be the most favorable in diet and living habits, which is prone to emotional fluctuations and anxiety, and will also affect the development and growth of the fetus.
Therefore, it is only a general and one-sided statement that the first-born fetus will be better, mainly depending on the mother's conditioning of her body and emotional stability. If you have a plan or are pregnant with your first child, I wish your mother and son peace and good health!