Hello and thank you for using healthcaremagic. I understand your concern about events. Before talking about susten and spotting, first something about normal pregnancy. In a normal pregnancy spotting and sometimes even menstrual bleeding can occur upto 12 weeks of pregnancy. Mostly it is harmless, barring a few condition like reduced progesterone which can cause problems for the baby. For a normal pregnancy to continue the body needs to be able to secrete a hormone called progesterone. If it is secreted in adequate quantities the the pregnancy goes on normally. For the 1st 2 months of pregnancy it is produced by ovaries. There after, the placenta takes over the function for the rest of the pregnancy. If sufficient quantity of progesterone is not secreted, there is a chance of pregnancy loss/abortion . Here comes the role of susten, which is an artificial progesterone, which keeps the pregnancy viable till the body is able to do so by itself, or till the end of pregnancy. Probably your doctor has documented reduced progesterone in your blood work, and hence susten. Susten buy itself doesn t cause spotting. Hope you have a normal pregnancy and childbirth. I hope to have cleared your queries with adequate information. If you have any more queries feel free to ask. Thanks again.