It's been sinking since 2000s and intuitively, Indian TFR is not high enough to explain such low female labour force participation, where world average is 50%. Also plenty of of countries with much better maternity benefits and significantly higher participation rates, but not fair to compare OECD. Culturally, I think it's driven by traditional social pressure for women to stay at home if husband can be bread winner, or jobs get deferred to men when times are tough.