美国还是加拿大？

https://www.nextsource.com/2015/05/14/the-laws-of-pregnancy-and-contractual-labor/

你自己看这篇文章，就知道你没有说清楚很多事实。

On appeal, the court found that only the primary employer, (Perma-Temp) was responsible for compliance with leave according to the FMLA.  Yet, the court ruled that the secondary employer (Keppel) did bear a conditional burden.  The secondary employer was obligated to accept a returning FMLA employee, provided they continued to engage the same staffing firm to fill that position. In this case, since the secondary employer replaced Cuellar without using Perma-Temp to fill the position, neither entity was found to have broken their FMLA obligations.

也就是说，你的孕妇身份主要是你的直接雇主（小老板）保护。在你的产假期间，你的合同雇主（大老板）可以用别的合同公司的人来替代你的合同。

但是如果你的合同雇主（大老板）用你的直接雇主（小老板）的其他人来代替你的合同，而且如果你的直接雇主（小老板）执意把你送回原职位，你的合同雇主（大老板）必须接受你回去。