Like Suse said, it'll most likely only work if your body is read to go into labour. But it is great for during labour especially if contractions start to fizzle out.

No harm in using it though if you use it correctly. Also, don't just use it once and think 'oh that didnt work' and not use it again. Keep trying. Make a time each day and massage your belly or bathe in it while burning some in an oil burner.