What causes spotting during pregnancy?

Light spotting is usually not serious and caused by one of the following:

* Implantation bleeding. In the earliest part of pregnancy, implantation of the embryo into your uterine wall causes spotting in about 20 to 30 percent of women. It usually occurs before (or in some cases around the time) you expected your period.
* Sex or an internal pelvic exam/pap smear. During pregnancy, your cervix becomes tender and engorged with blood vessels, and any kind of minor bumping (like intercourse or an internal exam) can sometimes irritate the cervix, causing some bleeding.
* Infection of the vagina (such as bacterial vaginosis) or cervix. Again, if your cervix is irritated or inflamed, it might bleed a little.
* Subchorionic bleed. Blood accumulates within the folds of the chorion (the outer fetal membrane, next to the placenta) or within the layers of the placenta itself, causing light to heavy spotting. In most cases, it resolves on its own and does not become a problem for the pregnancy.
* You’ve lost your mucous plug. Later in pregnancy, blood-streaked mucus may indicate the beginnings of labor.
What causes bleeding during pregnancy?

Vaginal bleeding can occur at almost any time in your pregnancy, on the other hand, is rarely an entirely benign sign. Because it can accompany any number of pregnancy complications, pinpointing the cause is best left to your gynecologist. Here are a few possible causes:

In your first trimester

* Ectopic pregnancy, where a fertilized egg implants outside of the uterus, requires immediate medical attention. You’ll notice sharp, crampy pain in your lower abdomen, often accompanied by nausea, vomiting, dizziness or weakness.
* Molar pregnancy is a rare condition discovered within weeks of conception where a placenta becomes a mass of cysts accompanied by a malformed or nonexistent embryo. You’ll sometimes also experience severe nausea, vomiting and cramping.
Late in your second trimester or anytime in your third

* Placenta previa, considered the most common cause of bleeding in the latter part of pregnancy, occurs when the placenta covers part of the cervix (your doctor should able to spot it on an ultrasound). In most women, the placenta moves away before birth, but placenta previa can lead to more serious conditions (like vasa previa, which occurs when the umbilical cord blocks the cervix), so be sure to consult your doctor right away.
* Placental abruption, which almost always occurs in the second half of pregnancy and usually in the third trimester, is the early separation of the placenta from the uterine wall. You’ll usually also notice abdominal aching or cramps, uterine tenderness and pain in the back or abdomen. If the separation is slight there’s usually little danger to you or your baby. But if it’s more severe, the risk to your baby is reasonably higher — which is why it’s so important to see your obstetrician .
* Preterm labor, or labor that starts anytime after week 20 and before week 37 of pregnancy, is accompanied by other signs of labor including regular contractions, period-like cramps, back pain and increased pelvic pressure. If you suspect labor is starting prematurely, contact your practitioner immediately.
What you need to know

Remember, light spotting is common and usually nothing to be concerned about. Heavy bleeding that soaks through a pad, however, always warrants a call to your doctor. But keep in mind, it’s not necessarily a sign that you’re miscarrying. Some women bleed — even heavily — throughout their pregnancies and still deliver healthy babies.