Spotting during pregnancy is common, affecting 15 to 25 percent of pregnancies in the first trimester alone. Most of the time, light spotting has a harmless explanation, but it can also signal something that needs medical attention. The cause depends heavily on how far along you are, how much blood there is, and whether you have other symptoms like pain.
Implantation Bleeding in Very Early Pregnancy
One of the earliest causes of spotting happens before many people even know they’re pregnant. When a fertilized egg attaches to the uterine lining, it can cause light bleeding about 10 to 14 days after ovulation. This is called implantation bleeding, and it’s often mistaken for a light or unusual period.
Implantation bleeding is typically pink or brown, not bright red. It looks more like vaginal discharge than a true period, lasting anywhere from a few hours to about two days. You might need a thin liner, but you won’t soak through pads or pass clots. If the blood is bright red, heavy, or contains clots, something else is likely going on.
Cervical Changes and Sensitivity
Pregnancy floods the body with estrogen, which changes the cervix in ways that make it more prone to bleeding. One common change is cervical ectropion, where delicate cells that normally line the inside of the cervix become visible on its outer surface. These cells are fragile and bleed easily when disturbed.
This is why spotting after sex is so common during pregnancy. A pelvic exam or even a Pap smear can trigger the same kind of light bleeding. It’s usually just a small amount of pink or brown blood that resolves on its own within a day or so, and it doesn’t pose a risk to the pregnancy.
Subchorionic Hematoma
A subchorionic hematoma is a pocket of blood that forms between the pregnancy membranes and the uterine wall. It’s the most common abnormality found on ultrasound in pregnancies that have a visible, living embryo. Among pregnancies with vaginal bleeding, 18 to 22 percent involve a subchorionic hematoma. The rate is even higher in pregnancies conceived through IVF, at roughly 22 percent compared to 11 percent in non-IVF pregnancies.
These hematomas often cause intermittent spotting or light bleeding, which can be alarming. The good news is that most of them, particularly small to moderate ones, resolve on their own as the pregnancy progresses. Your provider will likely monitor it with follow-up ultrasounds but may not recommend any specific treatment beyond watching and waiting.
Infections That Cause Spotting
Vaginal and cervical infections can irritate tissue enough to cause light bleeding during pregnancy. Sexually transmitted infections like chlamydia and gonorrhea are known culprits, as are urinary tract infections. These infections are treatable with antibiotics that are safe during pregnancy, but they need to be identified first. If your spotting comes with unusual discharge, odor, burning, or fever, an infection is worth investigating.
Ectopic Pregnancy
An ectopic pregnancy occurs when a fertilized egg implants outside the uterus, most often in a fallopian tube. It cannot develop into a viable pregnancy, and if the tube ruptures, it becomes a medical emergency.
The first warning signs are often light vaginal bleeding paired with pelvic pain. Some women initially have no symptoms at all, or they experience the same early pregnancy signs as anyone else: a missed period, nausea, breast tenderness. As the ectopic pregnancy grows, symptoms can become more specific. Shoulder pain or a sudden urge to have a bowel movement can occur if blood leaks internally and irritates nearby nerves. Extreme lightheadedness, fainting, or severe abdominal pain with bleeding are signs of rupture and require emergency care immediately.
Miscarriage
Spotting or bleeding in the first trimester can be a sign of miscarriage, though it’s important to remember that many pregnancies with early bleeding continue normally. A miscarriage typically involves bleeding that gets progressively heavier, along with cramping and the passage of tissue or clots. Brown spotting alone, without worsening symptoms, is less concerning than bright red bleeding that increases in volume.
Your provider can track whether the pregnancy is progressing by measuring levels of a pregnancy hormone in your blood over 48 hours. In a healthy early pregnancy, those hormone levels rise by at least 33 to 49 percent every two days, depending on the starting level. A slower rise raises concern for a miscarriage or ectopic pregnancy. Once you’re further along (around 10 weeks), ultrasound becomes the primary tool for checking on the pregnancy.
Late Pregnancy Causes
Spotting or bleeding in the second and third trimesters has a different set of causes, some of them serious.
Placenta Previa
Placenta previa means the placenta is covering part or all of the cervix. The hallmark symptom is bright red vaginal bleeding without pain, most commonly in the third trimester. Because the placenta is in a vulnerable position, bleeding can become heavy and dangerous. Placenta previa also raises the risk of preterm birth and slowed fetal growth.
Placental Abruption
Placental abruption happens when the placenta partially or fully separates from the uterine wall before delivery. Unlike placenta previa, abruption typically causes dark red bleeding accompanied by abdominal pain and contractions that don’t relax. You may also feel nauseous, thirsty, faint, or notice decreased fetal movement. Severe abruption is rare but dangerous because of the risk of uncontrolled hemorrhage.
The key distinction: painless bright red bleeding points toward placenta previa, while painful dark red bleeding with cramping suggests abruption. Both require prompt medical evaluation.
How Spotting Gets Evaluated
When you report spotting, your provider will typically start with a transvaginal ultrasound. This can detect a pregnancy in the uterus, identify ectopic pregnancies, reveal subchorionic hematomas, and check the location of the placenta. Signs of ectopic pregnancy, like a mass near the ovary or free fluid in the pelvis, can sometimes be spotted on ultrasound even very early on.
If it’s too early to see anything on ultrasound, your provider may use serial blood draws to track your pregnancy hormone levels over 48 hours. At hormone levels between 1,500 and 3,000, a pregnancy sac should be visible on ultrasound. One recent study found a 99 percent probability of seeing the sac once hormone levels reach about 3,510. If your levels are above that threshold and no pregnancy is visible in the uterus, your provider will investigate further for ectopic pregnancy or early loss.
When an early pregnancy is seen on ultrasound but viability is uncertain, a repeat scan in 7 to 10 days can confirm whether things are progressing.
Rh Factor and Spotting
If you have Rh-negative blood (your blood type has a minus sign, like A- or O-), any bleeding during pregnancy matters for an additional reason. Bleeding can allow small amounts of fetal blood to mix with yours, and if the fetus is Rh-positive, your immune system may develop antibodies against it. This can cause problems in future pregnancies. If you experience bleeding after 20 weeks, your provider will likely recommend an injection that prevents your body from forming these antibodies.
When Spotting Needs Emergency Attention
Light pink or brown spotting that stops on its own is rarely an emergency, but certain combinations of symptoms require immediate care. Head to an emergency department if you’re soaking through two pads per hour or passing large clots, experiencing severe or widespread abdominal pain (especially if it extends to your shoulders), feeling faint or dizzy, running a fever or having chills, or noticing foul-smelling discharge. These can indicate a ruptured ectopic pregnancy, heavy hemorrhage from a placental problem, or a serious infection, all of which need treatment quickly.