For many people, the second trimester marks a moment of calm in pregnancy. The intense symptoms of the first trimester often dissipate, and the exhaustion, muscle pain, and anxiety about birth that are common during the third trimester may not have appeared.
Small amounts of bleeding during the second trimester are typical and may not signal a problem, though it is important to get checked if something feels wrong. In this article, we look at the possible causes and when to see a doctor.
How much is normal?
Bleeding in the second trimester can cause mild inflammation and problems with the placenta or cervix.
Bleeding is common during the first trimester of pregnancy, affecting 15 to 25 percent of pregnant women.
Bleeding in the second trimester is less usual, with heavier bleeding being a more serious sign than light bleeding. Causes can range from mild inflammation to problems with the placenta or cervix.
Bleeding does not usually mean a woman is going into labor or having a miscarriage.
Women who experience mild bleeding, spotting, or unusual discharge should contact their healthcare providers. When bleeding is heavy or painful, it is a medical emergency.
Causes of bleeding in the second trimester
Possible causes of bleeding in the second trimester include:
Minor cervical irritation
Light spotting does not usually mean that there is a serious problem with the pregnancy, especially if the spotting goes away on its own within a day or two.
During pregnancy, the blood vessels in the cervix may become inflamed, especially when the weight of the uterus puts pressure on them. Some women can experience light bleeding after a pelvic exam or sex.
Cervical polyps are benign, or non-cancerous, growths on the cervix. They are common and rarely cause any problems.
During pregnancy, cervical polyps may swell or become irritated, causing them to bleed. A doctor can often carry out a quick exam to identify whether a cervical growth is a reason for a person's bleeding
The placenta is an organ that nourishes and protects the developing baby. Problems with this organ are a leading cause of bleeding during birth.
Anyone who suspects problems with the placenta must seek immediate treatment, as issues with the placenta can injure the baby and cause dangerous bleeding in the pregnant woman.
Some placenta issues that may cause bleeding in the second trimester include:
- Placenta previa: This is when the placenta is very low in the uterus. It may fully or partially cover the cervix, causing bleeding throughout pregnancy. In severe cases, doctors may recommend extra monitoring or a cesarean delivery.
- Placenta accreta: Placenta accreta causes the placenta to grow much deeper into the uterus than usual. It is more likely to cause bleeding during the third trimester than the second, however. During delivery, the bleeding may become life-threatening, so healthcare professionals will monitor the pregnancy carefully, often in a setting with emergency medical care, which may be critical to the mother's safety.
- Placenta abruption: Sometimes the placenta detaches from the uterus too early. It can cause bleeding, back pain, and intense stomach cramps. Early diagnosis can prevent severe complications to the woman and the baby.
Bleeding can be an early sign of labor. Some women may also notice an unusual discharge, called a mucous plug. A mucous plug looks like a combination of vaginal discharge, mucous, and blood.
When labor begins before 37 weeks, it is more likely that the baby will need to stay in the intensive care unit and may also experience other problems. During the second trimester, preterm labor endangers the baby's life.
Bleeding can be a risk factor for preterm labor. Women who have a history of bleeding during the second trimester can talk to their doctors about whether they are at risk of preterm labor and how best to minimize that risk.
Vasa previa is a problem with the baby's blood vessels. It causes some of the baby's blood vessels to run parallel to the cervix, left unprotected by the umbilical cord or placenta. These blood vessels may cause unusual bleeding, especially late in pregnancy or during preterm labor.
When the membranes burst, these vessels may also burst. Women with vasa previa usually have a cesarean delivery. A woman with a history of preterm labor or bleeding who has contractions or other intense pain should go to the emergency room.
Uterine rupture happens when the uterus tears. This can endanger the mother and the baby by causing severe bleeding and depriving the baby of oxygen. It can also trigger labor.
A woman who experiences bleeding, pain, a fever, or who has recently suffered an injury to the stomach or uterus may be experiencing a uterine rupture and should go to the emergency room.
Gestational trophoblastic disease
Gestational trophoblastic disease (GTD) is a group of rare diseases that causes abnormal cells to grow in the uterus during and after pregnancy. These cells can form tumors and masses. Sometimes these masses turn cancerous, though most forms of GTD are benign.
Women with GTD may have bleeding and an unusually large uterus.
Treatment depends on the type of GTD, how large the growth is, and other factors. A surgeon may need to remove the mass during or after pregnancy.
When to get emergency help
A person should seek emergency medical help if they experience sudden heavy bleeding.
Not all bleeding during the second trimester is an emergency. In many cases, the woman and the baby are fine.
Nevertheless, it is important to be cautious. Prompt intervention in emergencies can save the life of both the woman and the baby. Anyone who is uncertain should go to the emergency room.
Some symptoms that warrant emergency treatment include:
- bleeding after an injury, such as a car accident or fall
- sudden heavy bleeding
- bleeding that is getting progressively heavier
- bleeding that includes blood clots
- bleeding along with pain or contractions
- dizziness or weakness along with bleeding
- bleeding in a person with placenta accreta, placenta previa, or a history of preterm labor
When to call a doctor
Tell a doctor about any bleeding episodes to ensure a prompt and accurate diagnosis. Anyone who is uncertain about their bleeding should call right away.
Bleeding during the second trimester can be worrying. However, even when the bleeding is due to a serious complication, most women go on to have healthy pregnancies and babies.
Prompt medical care can prevent complications and save lives, so always talk to a provider about any bleeding, even if it seems minor.