Twins and hCG Levels | babyMed.com
1/31/2019 · In early pregnancy, a 48-hour increase of hCG by 35% can still be considered normal. As your pregnancy progresses, the hCG level increase slows down significantly. Between 1,200 and 6,000 mIU/ml serum, the hCG level usually takes 72-96 hours to double. Above 6,000 mIU/ml, the hCG levels often take over four or more days to double.