Did women work in production at the start of WWII and leading up to it?
The basic answer to this is “not very often.” However, that is not to say that there were no women working in production. There were relatively large numbers of women in some types of production, but there were generally not very many women at all in anything that would have been seen as heavy industry.
Before World War II, the vast majority of women worked in service industries. They worked as nurses and teachers and as domestics. There were, however, a large number of women who worked in some sort of production jobs. This did not mean, however, that they were making things like cars or airplanes. Instead, those who worked in production were largely doing light industrial work. That is, they were engaged in making cloth or clothing. They were processing food. They were working in tobacco plants in the South. These are jobs that can be seen as production, but they are not part of heavy industry.
Women did not start to move into heavy industry at the very beginning of World War II. That took longer. As more and more men went into the military, more women took industrial jobs.