What women used to be like during pregnancy.
Most women, like most men, did hard physical work all their lives, through most of human history. That included women throughout their pregnancies.
Pregnancy in itself is a normal condition of the female body: not a medical crisis, not trouble with a capital T.
Having said that, there are certainly times and conditions and situations in which women should take it easy. However, pregnancy in itself is a normal state. We forget that sometimes.