Blood clots and pregnancy
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.
Most women with blood clotting conditions have healthy pregnancies. But these conditions may cause problems for some pregnant women. In severe cases, they can cause death for both mom and baby. But testing and treatment can help save both you and your baby.
If you’re pregnant or trying to get pregnant and have had problems with blood clots in the past, tell your health care provider at a preconception checkup (before pregnancy) or at your first prenatal care checkup. Also tell your provider if someone in your family (your parent or a brother or sister) has had problems with blood clots. This means the condition may be in your family history (run in your family).
If you or someone in your family has had problems with blood clots, talk to your provider about getting a blood test to see if you have a thrombophilia. This is a health condition that increases your chances of making abnormal blood clots. Some pregnant women with thrombophilias need treatment with medicines called blood thinners. They stop clots from getting bigger and prevent new clots from forming.
Who is at risk for having blood clots?
Certain things make you more likely than others to have a blood clot. These are called risk factors. Having a risk factor doesn’t mean for sure that you’ll have a blood clot. But it may increase your chances. Talk to your health provider about what you can do to help reduce your risk.
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.
- Having certain health conditions, like a thrombophilia, high blood pressure, diabetes or being overweight or obese. A family history of blood clotting problems also increases your chances of blood clots.
- Taking certain medicines, like birth control pills or estrogen hormones. These medicines can increase the risk of clotting. If you’ve had problems with blood clots or thrombophilias or have a family history of these conditions, birth control pills may not be safe for you to use. 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, like a cesarean section (also called c-section). A c-section is a surgery in which your baby is born through a cut that your doctor makes in your belly and uterus. The American College of Obstetricians and Gynecologists (ACOG) 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.
What problems can blood clots cause during pregnancy?
If you have a blood clot or a kind of thrombophilia called antiphospholipid syndrome (also called APS), 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 (also called 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. PE 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
- Feeling anxious
- Coughing up blood
Stillbirth. This is when a baby dies in the womb before birth but 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:
- Cerebral vein thrombosis (also called CVT). This happens when a blood clot forms in a vein in the brain. CVT can lead to stroke. Signs and symptoms include headache, vision problems and seizures.
- Deep vein thrombosis (also called DVT). This happens when a blood clot forms in a vein deep in the body, usually in the lower leg or thigh. DVT can be diagnosed with ultrasound or other imaging tests. Signs and symptoms may include warmth and tenderness over the vein and pain, swelling or skin redness in the affected area.
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.
How are these conditions treated?
Your provider may use tests like ultrasound or magnetic resonance imaging (also called MRI) to find out if you have a blot clot or clotting conditions. Ultrasound uses sound waves and a computer screen to make a picture of a baby in 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:
- Ultrasound to check your baby’s growth and development. She may use 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 (also called a nonstress test or NST). This test checks your baby’s heart rate in the womb and sees how the heart rate changes when your baby moves. Your provider uses this test to make sure your baby’s getting enough oxygen.
During pregnancy your provider may give you a blood thinner called heparin (low-molecular weight heparin or unfractionated heparin). 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 with heparin. Or he may treat you with a blood thinner called warfarin. Warfarin is safe to take after pregnancy, even if you’re breastfeeding. Warfarin is not safe to take during pregnancy because it may cause birth defects.
For more information
The Shane Foundation
Last reviewed February 2015
See also: Thrombophilias, Maternal death
Frequently Asked Questions
What is mononucleosis?
Mononucleosis (also called mono) is an infection usually caused by the Epstein-Barr virus (EBV). It’s sometimes caused by another virus called cytomegalovirus (CMV). EBV and CMV are part of the herpes virus family. Mono is most common in teenagers and young adults, but anyone can get it. Mono is called the “kissing disease” because it’s usually passed from one person to another through saliva. In addition to kissing, it can also be passed through sneezing, coughing or sharing pillows, drinks, straws, and toothbrushes.
You can have mono without having any symptoms. But even if you don’t get sick, you can still pass it to others. Symptoms can include:
- Achy muscles
- Belly pain
- Fatigue (feeling tired all the time)
- Sore throat
- Swollen glands in your neck
If your symptoms don’t go away or get worse, tell your health care provider. He’ll most likely do a physical exam and test your blood to find out for sure if you have mono.
There’s no vaccine to prevent mono. There’s also no specific treatment. The best care is to take it easy and get as much rest as you can. It may take a few weeks before you fully recover.
Can Rh factor affect my baby?
The Rh factor may be a problem if mom is Rh-negative but dad is Rh-positive. If dad is Rh-negative, there is no risk.
If your baby gets her Rh-positive factor from dad, your body may believe that your baby's red blood cells are foreign elements attacking you. Your body may make antibodies to fight them. This is called sensitization.
If you're Rh-negative, you can get shots of Rh immune globulin (RhIg) to stop your body from attacking your baby. It's best to get these shots at 28 weeks of pregnancy and again within 72 hours of giving birth if a blood test shows that your baby is Rh-positive. You won't need anymore shots after giving birth if your baby is Rh-negative. You should also get a shot after certain pregnancy exams like an amniocentesis, a chorionic villus sampling or an external cephalic version (when your provider tries to turn a breech-position baby head down before labor). You'll also want to get the shot if you have a miscarriage, an ectopic pregnancy or suffer abdominal trauma.
I had a miscarriage. How long should I wait to try again?
Before getting pregnant again, it's important that you are ready both physically and emotionally. If you don't need tests or treatments to discover the cause of the miscarriage, it's usually OK for you to become pregnant after one normal menstrual cycle. However, it may take longer for you to feel emotionally ready to be pregnant again. Everyone responds differently to a miscarriage. Only you will know when you are ready to try to get pregnant again.
Are gallstones common during pregnancy?
Not common, but they do happen. Elevated hormones during pregnancy can cause the gallbladder to function more slowly, less efficiently. The gallbladder stores and releases bile, a substance produced in the liver. Bile helps digest fat. When bile sits in the gallbladder for too long, hard, solid nuggets called gallstones can form. The stones can block the flow of bile, causing indigestion and sometimes serious pain. Staying at a healthy weight during pregnancy can help lower your risk of gallstones. Exercise and eating foods that are low in fat and high in fiber, like veggies, fruits and whole grains, can help, too. Symptoms of gallstones include nausea, vomiting and intense, continuous abdominal pain. Treatment during pregnancy may include surgery to remove the gallbladder. Gallstones in the third trimester can be managed with a strict meal plan and pain medication, followed by surgery several weeks after delivery.