Irrespective of the size of the organization one should look into statutory compliance when any particular Labor Law becomes applicable to it rather than the industry practice.
You may, please, refer to the definition of the term "woman" u/s 3(o) of the Maternity Benefit Act,1961 which means a woman employed, whether directly or through any agency, for wages in any establishment.
Yes. Contract employees are also entitled to maternity leave of 180 days. As per the Maternity Benefit Act, 1961, every woman employee working in any establishment is entitled to maternity leave of 180 days.