Ovulation usually occurs 14 days before the next menstrual cycle. Implantation can occur as early as 5 or 6 days after conception or as late as 11 or more days after fertilization. Older research indicates that the days 8, 9, and 10 DPO are the most prevalent for successful implantation. More recent studies have shown that the risk of miscarriage increases if implantation does not occur by day 10. Because of this, some clinicians recommend that women avoid pregnancy tests on days 11 and 12 to allow time for an embryo to become implanted. Early pregnancy symptoms include mood changes, nausea, and vaginal bleeding. If you think you may be pregnant, it is important to call your doctor immediately to confirm the diagnosis and begin treatment plans as soon as possible. It is normal to experience some bleeding during pregnancy. The amount will vary from woman to woman depending on their age, previous pregnancies, and other factors. Some women may even notice they are bleeding heavily one day and hardly at all the next. This is known as "menses irregularity" and it is entirely normal. If you do not bleed regularly throughout your pregnancy then this could be a sign that you have suffered a loss earlier in your pregnancy. See your doctor to determine the cause of the irregular bleeding. Implantation bleeding is the term used to describe the light spotting or bleeding between one and four weeks after conception.