Both the common yeast infection and common bacterial vaginosis can also cause bleeding. Bacterial vaginosis is a harmless infection but has been linked to a possible increase in risk of preterm labor later on. A microscopic evaluation can diagnose both these infections. Pills and antibiotic gel easily get rid of them.
Cervical polyps are another reason for bleeding. These are delicate, benign overgrowths of internal cervical cells that protrude into the vagina. You may get polyps for the first time because the increased estrogen of pregnancy makes them grow suddenly into a noticeable size. A cervical polyp can bleed from intercourse or even just from walking. Polyps can be twisted off in the office or watched until delivery when a passing baby destroys them.
Sometimes a small piece of tissue becomes loose and disintegrates for some reason, which can also cause spotting. It's usually a hormonally stimulated collection of menstrual-like tissue debris, which can often be confused with a miscarriage but means nothing. However, if it's actual fetal or placental tissue, then there is serious concern of risk for a miscarriage.
Sexually transmitted diseases, such as gonorrhea, chlamydia, and trichomonas, can cause bleeding—and are more worrisome. Chlamydia and gonorrhea infections may be silent for years, so even if there is no suspicion of infidelity for a couple now, there may have been an infection long before they even met each other. Cultures for STDs have become standard in all pregnancies.
Reasons for a Possible Miscarriage
Any first-trimester bleeding may be a threatened miscarriage and needs to be proven otherwise. Also, the cramping of a threatened miscarriage can feel exactly like the growing pains of a normal uterus. In early pregnancy, a threatened miscarriage also presents with abnormally low progesterone. (It is still unclear whether the baby is threatened because the progesterone is low, or that the progesterone is low because the baby is threatened.)
Fortunately, obstetricians now have the tools to give a patient peace of mind. For instance, blood tests can prove that the pregnancy hormone is increasing as expected, confirming a healthy pregnancy. Also, ultrasound can demonstrate the physical well-being of a growing baby by showing a healthy heart rate or by ruling out an ectopic pregnancy (a pregnancy outside of the uterus, usually in a fallopian tube).