Nature’s Stress Test: Understanding How Pregnancy Affects Your Heart

Your heart pumps about 30-50% more blood during pregnancy than it does when you’re not pregnant. This increased workload begins early in your first trimester and continues through delivery, making pregnancy one of the most cardiovascularly demanding experiences your body experiences.

At The Birth Center of New Jersey in Union, New Jersey, our certified professional midwives understand the cardiovascular changes that come with pregnancy. We monitor your heart health throughout your time with us and help you recognize when changes fall within normal ranges versus when they need closer attention.

How pregnancy changes your cardiovascular system

Changes to your heart function start early in pregnancy — often before you even get a positive test — and affect everything from your resting heart rate to your blood volume.

Blood volume increases dramatically

Your body produces about 50% more blood during pregnancy, with most of this increase happening by the end of your second trimester. This extra blood feeds the placenta, supports your baby’s growth, and prepares your body for blood loss during delivery.

Heart rate climbs

Your resting heart rate rises by 10-20 beats per minute during pregnancy. What felt like a normal 70 beats per minute before pregnancy might jump to 85-90 beats per minute by your third trimester.

This faster heartbeat helps move the increased blood volume through your body. You might notice your heart pounding when you're lying down or feel your pulse racing after climbing stairs. Both are normal responses to your body’s increased demands.

Blood pressure drops, then rises

Blood pressure typically decreases during the first half of pregnancy as your blood vessels relax and widen. This drop can lead to dizziness when you stand up quickly or cause lightheadedness in warm environments.

By your third trimester, your blood pressure usually returns to pre-pregnancy levels. Your expanding uterus also puts pressure on the large vein that returns blood from your lower body to your heart, which is why lying flat on your back can make you feel faint later in pregnancy.

Normal cardiovascular symptoms during pregnancy

Your heart is working harder than usual, and that shows up in ways that can feel alarming, even when everything is functioning exactly as it should. You might experience:

• Shortness of breath as your uterus pushes your diaphragm upward
• Heart palpitations when lying down or after physical activity
• Swelling in your feet, ankles, and hands
• Fatigue as your body builds the placenta and grows your baby

These symptoms stem from your body’s increased demands rather than heart problems. Your lungs have less room to expand, and your cardiovascular system is working overtime to support both you and your baby.

Cardiovascular red flags during pregnancy

Some warning signs mean your heart needs help or that a serious complication is developing, including:

Severe or sudden shortness of breath

Breathlessness that comes on quickly or wakes you from sleep can indicate heart failure or blood clots in your lungs. 

Chest pain or pressure

Pain that spreads to your arm, neck, or jaw, or that comes with sweating and nausea, needs emergency assessment. 

Irregular heartbeat with other symptoms

An irregular heart rhythm that feels sustained, chaotic, or makes you feel faint differs from occasional palpitations. 

Severe headaches with vision changes

Headaches paired with vision problems, upper abdominal pain, or significant swelling can signal preeclampsia, a serious pregnancy complication that affects your cardiovascular system and other organs.

Fainting or near-fainting

Actually losing consciousness or coming very close indicates your heart isn’t maintaining adequate blood flow to your brain.

Protecting your heart during pregnancy

Your cardiovascular system needs support to handle the extra work pregnancy demands. A few key habits can help, such as:

• Attending all prenatal care appointments for regular monitoring
• Staying physically active through walking, swimming, or prenatal yoga
• Managing your weight gain within recommended ranges
• Limiting sodium to prevent excess fluid retention
• Trusting your instincts and seeking care when something feels wrong

Pay attention to how you feel during exercise rather than trying to hit specific heart rate targets. If something feels off or different from the usual pregnancy discomforts, get it checked.

Schedule your prenatal care 

Understanding how pregnancy affects your heart helps you know what to expect and when to seek care. At The Birth Center of New Jersey, we monitor your cardiovascular health throughout your pregnancy and postpartum.

To schedule a prenatal appointment or discuss your heart health during pregnancy, call our office at 908-627-4455 or book a visit online.