Many countries, rich and poor, and of varying cultures, allow women to fly fighters. USA, Indonesia, Singapore, Pakistan, China, Israel, Russia, Serbia, Uruguay, Brazil, Ethiopia (the first missile kill achieved by a woman was by Capt. Aster Tolossa who flew a Su-27 flanker that shot down a mig 29), Norway, South Africa, New Zealand, South Korea, Nigeria....and more.
If all these countries, even dirt poor ones like Ethiopia can invest in female fighter pilots, I am sure that India can too. Why did all these countries decide to invest in their training, although few of them are teeming with cash? Didn't the question of pregnancy come up in these countries? I don't see why a way cannot be found around the issue of pregnancy. For one thing, I don't think that your assertion that they cannot fly anymore after delivering a baby is true. It will be their duty to train and stay in shape. (actresses do it all the time, so why can't warriors? If aishwarya rai can get back to being slim and curvy in a year after pregnancy, I don't see why trained air warriors can't get back in shape.)
So although a year and a half will be lost during pregnancy, they can still be made to put in the mandatory number of flying years. Besides, although a law can't be made against them getting pregnant, they can certainly be discouraged from getting pregnant multiple times, there are lots of ways to pressure them on that. Their career advancement will suffer if they do not give their best for the service and for the nation. Besides, so many women in private jobs plan their family with their career in mind (some call them career oriented rather than family oriented.) Women who work for a living do not usually have ten children like women who are confined to their homes do.
Also, it's not like every woman pilot who enters the fighter stream will get pregnant and leave the force. Only a very small percentage will. After all, a fighter pilot's job wont be handed to them on a platter, it will have to be earned through very hard work. And all that time, they will be well aware of these issues, and they would bear all that in mind while struggling to get selected as a fighter pilot. They get there only because they have volunteered to serve the nation, and because they worked hard for it. If they have the determination to become a fighter pilot, and to train themselves to fly F-16s or flankers, they will not simply get pregnant and leave after a year or two. Only people who are that dedicated and motivated reach those positions in the first place. If a few of them do become a liability because they get pregnant multiple times, that would be a cost we have to bear for giving one gender their rights. After all, hundreds of pilots took premature retirement in the 2000s, to join private airlines. (263 pilots between 2002 and 2004 alone.) The number of pilots who get pregnant multiple times will be miniscule compared to that wastage.
By the way, talking about pregnancy and flying fighters:
That's Major Stephanie Kelsen, who has been flying F-16s for the past 23 years, and mothered two children in between. She was the commander of a major air national guard unit in 2009. Here she is, maneuvering her F-16 into position for an aerial refueling: