Blood Clots and Pregnancy

Source: March of Dimes

A blood clot (also called a thrombosis) is a mass or clump of blood that forms when blood changes from a liquid to a solid.

The body normally makes blood clots to stop the bleeding after a scrape or cut. But sometimes blood clots can partly or completely block the flow of blood in a blood vessel, like a vein or artery. This can cause damage to body organs and even death.

If you are pregnant or are trying to get pregnant and have had problems with blood clots in the past, tell your physician at your first prenatal care checkup. Also tell your provider if someone in your family has had problems with blood clots. This means the condition may be in your family history.

Attention New Moms
Know the Symptoms of Deep Vein Thrombosis (Blood Clot) That Could Save Your Life [PDF]

Symptoms to know

Pulmonary Embolism (PE) is when a blood clot breaks free and travels to the lungs.

It can block blood flow and can be life-threatening. This is an emergency and a leading cause of death during pregnancy.

Call 911 or an ambulance immediately if you have any of the following symptoms:

  • Shortness of breath or difficulty breathing
  • Sharp or stabbing pain in your side, back or chest that may worsen with deep breaths
  • Fast heart beat
  • Fast breathing
  • Sudden, unexplained cough (may have bloody mucus)

Who is at risk for having blood clots?

Certain things may increase your chances of having a blood clot. Risk factors for blood clots include:

  • Being pregnant. Your blood clots more easily during pregnancy to help your body get ready to lessen blood loss during labor and birth. Also, blood flow in your legs gets slower late in pregnancy. This is because the blood vessels around your pelvis and other places are more compressed (narrow) and your growing uterus (womb) puts pressure on your pelvis
  • Health conditions. Thrombophilia, disseminated intravascular coagulation (DIC), high blood pressure, diabetes or being overweight or obese. A family history of blood clotting problems also increases your chances of blood clots.
  • Certain medicines. Birth control pills or estrogen hormones. These medicines can increase the risk of clotting. Talk to your health care provider about other birth control options.
  • Smoking. Smoking damages the lining of blood vessels, which can cause blood clots to form.
  • Having surgery. A cesarean section (also called c-section) is considered surgery. The American College of Obstetricians and Gynecologists recommends that doctors help prevent blood clots in women during a c-section. This may include using compression devices that put pressure on your legs to help keep your blood flowing during the c-section.
  • Being dehydrated. This means you don’t have enough water in your body. Dehydration causes blood vessels to narrow and your blood to thicken, which makes you more likely to have blood clots.
  • Not moving around much. This may be because you’re on bed rest during pregnancy or recovering from surgery or an accident. Being still for long periods of time can lead to poor blood flow, which makes you more likely to have blood clots. Even sitting for long periods of time, like when travelling by car or plane, can increase your chances of having a blood clot
  • Having a baby. You’re more likely to have a blood clot in the first 6 weeks after birth than women who haven’t given birth recently.

How are blood clots treated?

  • Your obstetrician may use tests like ultrasound or MRI to find out if you have a blot clot or clotting conditions.
    • Ultrasound uses sound waves and a computer screen to show a picture of your baby inside the womb. 
    • MRI uses magnets and computers to make a clear picture of the inside of the body. These tests are painless and safe for you and your baby.
  • If you’re pregnant and have a clotting condition, you may need to go for prenatal care checkups more often than women who don’t have these blood clot conditions. At these visits, your provider checks your blood pressure and can use other tests, like blood tests, to monitor your health.
  • Your provider also checks your baby’s health in the womb using tests like:
    • A special kind of ultrasound called Doppler to check your baby’s blood flow in the umbilical artery, a blood vessel in the umbilical cord. The umbilical cord connects your baby to the placenta. It carries food and oxygen from the placenta to the baby. 
    • Fetal heart rate monitoring to check your baby’s heart rate in the womb and sees how the heart rate changes when your baby moves to make sure your baby’s getting enough oxygen. 
  • During pregnancy your provider may give you a blood thinner. Your provider also may refer you to a hematologist. This is a doctor who treats blood conditions. 
  • After you give birth, your provider may continue to treat you a blood thinner. 

What problems can blood clots cause during pregnancy?

If you have a blood clot you may be more likely to have complications that can affect your health and your baby’s health, including: 

  • Blood clots in the placenta. The placenta grows in your uterus (womb) and supplies the baby with food and oxygen through the umbilical cord. A blood clot in the placenta can stop blood flow to your baby and harm your baby. 
  • Heart attack. This usually happens when a blood clot blocks blood and oxygen flow to the heart. Without blood and oxygen, the heart can’t pump blood well, and the affected heart muscle can die. A heart attack can lead to lasting heart damage or death. 
  • Intauterine growth restriction (IUGR). This is when your baby grows poorly in the womb. 
  • Miscarriage. A miscarriage is when a baby dies in the womb before 20 weeks of pregnancy.
  • Placental insufficiency. This is when the placenta doesn’t work as well as it should so your baby gets less food and oxygen.
  • Preeclampsia. Preeclampsia is a condition that can happen after the 20th week of pregnancy or right after pregnancy. It’s when a pregnant woman has high blood pressure and signs that some of her organs, like her kidneys and liver, may not be working properly. Some of these signs include having protein in the urine, changes in vision and severe headache. 
  • Premature birth. This is when your baby is born before 37 weeks of pregnancy. 
  • Pulmonary embolism (also called PE). An embolism is a blood clot that moves from where it formed to another place in the body. When the clot moves to a lung, it’s a PE and can cause low oxygen levels in your blood and damage your body organs. It’s an emergency and a leading cause of death during pregnancy. Signs and symptoms of PE may include:
    • Trouble breathing
    • Fast or irregular heartbeat
    • Chest pain
    • Fainting
    • Feeling anxious
    • Coughing up blood
  • Stillbirth. This is when a baby dies in the womb after 20 weeks of pregnancy.
  • Stroke. This happens when a blood clot blocks a blood vessel that brings blood to the brain, or when a blood vessel in the brain bursts open. Pregnancy and childbirth cause strokes in about 8 in 100,000 women. Stroke can cause lasting damage to the body or death.
  • Thrombosis. This happens when a blood clot forms in a blood vessel and blocks blood flow. It most often happens in the deep veins of the legs but can be in other places of the body.
  • Venous thromboembolism (also called VTE). This happens when a blood clot breaks off and travels through blood to vital organs, like the brain, lungs or heart. This condition includes DVT and PE. VTEs that block blood vessels in the brain or heart can cause stroke or heart attack.