BABY2BEE.. i have just found this but i really have no idea hun but trying to help ya ok im no dr pmsl.....dr smith lol...

Before pregnancy: 1 to 28 ng/ml
Conception to 12 weeks: 9 to 47 ng/ml
12 to 28 weeks: 17 to 146 ng/ml
28 weeks till birth: 55 to 200 ng/ml