What all pregnant women should know about blood clots

For several hundred years, and as recently as 40 years ago, women were advised to decrease physical activity in the days leading up to delivery, as well as a few weeks after. The thought was that staying in bed would allow a woman to save her energy for labor and recovery after the baby was born. That’s why one of the first maternity hospitals in Great Britain was called the General Lying-In Hospital.

Today, we now know the exact opposite is true: Women should remain active right up to delivery, and they should get up and walk as soon as possible after delivery to reduce the risk of potentially harmful blood clots, even after a cesarean section (C-section). While the overall risk of this happening is low – one or two cases for every 1,000 deliveries – almost 10 percent of maternal deaths in the U.S. are related to blood clots that travel to the lungs. It’s split fairly evenly, with half of the clots happening before delivery and half afterward.

Unfortunately, too many women aren’t aware of this risk. Not long ago in our clinic, I checked on a patient who’d delivered about a week earlier and had a painful sore on her thigh. I asked, “Does it hurt when you walk?” The patient looked baffled and said she’d been in bed all week. I explained that changes in a woman’s body during pregnancy create a prime opportunity for blood to pool in the legs, where clots can form easily. If a clot breaks free, it can travel to the lungs, causing shortness of breath, low oxygen levels, and even death if left untreated. 

Thankfully, this patient was fine, and she left with a better understanding of healthy postpartum activities. But her story easily could have gone the other way. It’s important for women to know the symptoms of a blood clot and how to prevent them during and after pregnancy.

Why does this happen?

Pregnancy poses an unusual set of circumstances that predispose women to the development of clots. First, as any pregnant woman who developed varicose veins during pregnancy can tell you, the growing uterus puts pressure on veins in the pelvis and the major vein returning blood from the legs. The sluggish return of blood predisposes to the development of clots. Second, factors in the blood that favor the development of clots are increased in pregnancy.

Signs of blood clots before and after delivery

Blood clots related to pregnancy tend to have specific symptoms, depending on whether the clot is located to the leg or has traveled to the lung. Evidence of blood clots in the extremities, which is more common before delivery, include the abrupt development of:

● Tenderness in the affected area

● Swelling of the affected leg

● Warmth over the clot location

Blood clots to the lung, which are more common following delivery, manifest as experiencing chest pain, coughing (including coughing up blood), and fainting.

The diagnosis is fairly straightforward, depending on what we are suspicious for. We use an ultrasound to examine the flow of blood through the legs and to check for any blockages. Magnetic resonance imaging also can be useful. Special CT tests look for blood clots in the pulmonary vessels. 

Risk factors for developing clots

Any pregnant woman is at increased risk for developing a blood clot. However, some women have additional factors that put them at increased risk. Factors specific to pregnancy include diabetes, preeclampsia, or a having a C-section delivery. Prolonged bedrest, say for preterm labor or premature rupture of the membranes, also will add additional risk. 

Other general conditions that increase a pregnant woman’s risk include age over 35, being obese, and being a smoker. Women who have a known genetic predisposition for developing clots are at highest risk during pregnancy.

How providers and patients can prevent blood clots

If bed rest is necessary due to an obstetric complication, your provider should assess your risk. If indicated, you might need to take blood thinners during pregnancy or following delivery. If a woman requires a C-section, we generally place sequential compression devices on her legs. These devices gently squeeze the calf muscles, reducing pooling of blood and improving return to the heart. 

It’s important to follow your doctor’s recommendations about resuming activity as soon as possible after delivery. At the hospital, we’ll have you up and walking around within hours of delivery. Even after a C-section, we’ll remove your bladder catheter and have you at least sitting up in a chair within a few hours of surgery. Don’t be surprised if we encourage you to walk a few steps that same day.

It’s important to continuing moving once you get home as well. We aren’t asking that you start an exercise routine immediately – walking to the bathroom, going to a chair to hold your newborn, and moving around your home in general is all it takes to reduce your risk for developing a blood clot. Women at particular risk, including those with a history of blood clots or those who developed clots in the hospital, might need additional measures to prevent the development of blood clots.

Pregnancy and the weeks following delivery are a high-risk time for developing blood clots, which can cause serious health problems if not detected early. But with proper interventions, more women can reduce the risk of dangerous blood clots related to pregnancy.

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