A threatened miscarriage is vaginal bleeding that occurs before 20 weeks of pregnancy while the cervix remains closed and the pregnancy is still viable. It does not mean a miscarriage is happening or will happen. In most cases, the pregnancy continues normally, but the bleeding signals that closer monitoring is needed. The term can sound alarming, but it describes a possibility, not an outcome.
What It Looks Like
The hallmark symptom is vaginal bleeding in the first half of pregnancy, most commonly during the first trimester. The bleeding is typically mild and may range from light spotting to something closer to a light period. Some women also experience lower abdominal cramping or a dull backache, while others have bleeding with no pain at all.
What distinguishes a threatened miscarriage from other types is the status of the cervix. In a threatened miscarriage, the cervix stays closed. If the cervix begins to open, the diagnosis shifts to an “inevitable miscarriage,” meaning the pregnancy can no longer continue. In a missed miscarriage, the embryo or fetus has stopped developing, but there’s no bleeding or cervical opening, so the person may not know anything is wrong until an ultrasound.
How Doctors Assess the Pregnancy
When you show up with bleeding in early pregnancy, the first step is usually an ultrasound. The main question is whether the pregnancy has a heartbeat. A fetal heart rate below 120 beats per minute in the first trimester is associated with a higher risk of pregnancy loss. Heart rates at or below 85 bpm carry the most concern, while rates above 120 bpm are reassuring. That said, a slower heart rate doesn’t guarantee a bad outcome, and a normal rate doesn’t guarantee a good one. It’s one piece of a bigger picture.
Your provider may also check hormone levels in your blood. In a viable early pregnancy, levels of the pregnancy hormone hCG rise predictably. A rise of more than 75% over 48 hours is strongly associated with a continuing pregnancy. If levels plateau or drop, it may suggest the pregnancy is not progressing. In many cases, though, a single blood draw isn’t enough, and you’ll need repeat testing a couple of days later to see the trend.
Subchorionic Hematoma
One of the most common findings on ultrasound during a threatened miscarriage is a subchorionic hematoma, which is a pocket of blood that collects between the uterine wall and the pregnancy sac. Up to about 30% of women with threatened miscarriage bleeding have one. Many subchorionic hematomas resolve on their own as the pregnancy grows, though larger ones may be linked to a higher risk of preterm delivery. Your provider will likely monitor the size of the hematoma on follow-up ultrasounds.
What Causes It
In many cases, there’s no clear explanation for the bleeding. The developing placenta is burrowing into the uterine lining during the first trimester, and this process can cause some bleeding that has nothing to do with the health of the pregnancy. Subchorionic hematomas, as described above, are another common cause.
When a threatened miscarriage does progress to an actual miscarriage, chromosomal abnormalities in the embryo are the most frequent underlying reason. These are random errors in cell division that happen at conception and are not caused by anything the mother did or didn’t do. Other contributing factors can include uterine abnormalities, hormonal issues, or certain medical conditions, but the majority of early pregnancy losses come down to genetics that were never viable from the start.
Treatment and What Actually Helps
This is where expectations often clash with reality. There is no proven intervention that prevents an early pregnancy loss. The American College of Obstetricians and Gynecologists states this directly: therapies historically recommended, including bed rest, pelvic rest, vitamins, and uterine relaxants, have not been shown to prevent miscarriage. Bed rest in particular is specifically not recommended, despite being one of the most common pieces of advice women receive from well-meaning friends and family.
One area where evidence is evolving is progesterone supplementation. The PRISM trial found that vaginal progesterone increased live birth rates in women who had bleeding in early pregnancy and a history of prior miscarriages. For women experiencing their first episode of threatened miscarriage with no history of loss, the benefit was less clear. Some providers will prescribe progesterone for women with recurrent miscarriage who present with early bleeding, but this isn’t a universal standard.
In practical terms, “treatment” for most women with a threatened miscarriage means monitoring. You’ll likely have one or more follow-up ultrasounds to confirm the pregnancy is progressing, and repeat blood work if your initial hormone levels were borderline. You can continue your normal daily activities.
Blood Type Considerations
If you have Rh-negative blood (your blood type has a negative sign, like A- or O-), your provider may discuss whether you need a shot of Rh immune globulin. This medication prevents your immune system from developing antibodies against the baby’s blood cells if they have Rh-positive blood. Historically, this shot was given after any bleeding event in pregnancy. More recent evidence suggests that before 12 weeks, the risk of sensitization from bleeding is extremely low, so some providers may hold off on administering it until later. Your provider will make this call based on how far along you are and current guidelines at your facility.
What Happens Next
The majority of threatened miscarriages do not end in pregnancy loss. Many women experience a single episode of bleeding that resolves within days, and the rest of the pregnancy proceeds without complications. The bleeding can be frightening, but its presence alone is a poor predictor of outcome. The strongest predictors are the ultrasound findings (heartbeat present, normal heart rate) and rising hormone levels.
Some women have intermittent spotting that continues for weeks before stopping entirely. Others may have a second or third episode of heavier bleeding that requires re-evaluation. If the bleeding becomes heavy, soaking through a pad in an hour or less, or is accompanied by severe cramping, tissue passing from the vagina, or dizziness, the situation may be changing and needs prompt evaluation.
After a threatened miscarriage that resolves, most pregnancies are monitored a bit more closely in the weeks that follow. You may get an additional ultrasound or two beyond what’s normally scheduled. If a subchorionic hematoma was found, your provider will want to confirm it’s shrinking. By the second trimester, if the pregnancy is progressing normally, the risk drops significantly and the “threatened” label no longer applies.