A bit of bleeding during pregnancy can signal problems, but in most cases is usually no cause for worry. It is believed to occur in about one out of ten pregnant women. It usually happens during the first trimester as your reproductive system tries to adapt to its new role. A period during pregnancy is physiologically impossible; bleeding in this case is usually a discharge caused by some other process.

Bleeding during pregnancy is usually accompanied by a general feeling of heaviness. Some women have reported a lack of energy and light nausea. This is a result of your hormone levels changing as your womb tries to stem blood loss in areas where the placenta doesn’t cover it. This is called decidual bleeding and is completely normal during the first three months of pregnancy.

“Normal” bleeding is usually light; that is, no more than a few spots. The blood also tends to be dark or brown. If you lose more than a few drops and if the blood is bright red, it means there is active bleeding. In this case you should get some rest and call your doctor to get tested. The most common cause of this type of bleeding is a low-lying or detached placenta.

Bleeding that’s accompanied by sharp back or abdominal pain should also be brought to the doctor’s attention. Dark or brown spots in this case can signal a tubal or ectopic pregnancy (where the fetus is attached to the Fallopian tube or outside the womb, instead of inside it). This is rare, but if it’s the case it’s best to have it diagnosed as soon as possible.

A less common source of bleeding during pregnancy is a cervical polyp. These are usually benign and may even occur after you have sexual intercourse. You can opt to have them removed, but most doctors will only do this if it seriously obstructs fetal development (which is rarely the case). Vaginal infections and taking birth control pills before getting pregnant are also common causes of bleeding.

After the first trimester, bleeding should stop completely or at least slow down considerably. Any spots or drops past this point will potentially require medical attention, so pay extra attention to any discharges. While the cause isn’t always serious, getting in touch with your doctor and correcting any problems early on can prevent complications in the next few months, or even after childbirth.