Pregnancy and the heart: what changes and what to watch

A 2024 review in the Turkish Journal of Medical Sciences describes pregnancy as inducing significant cardiovascular changes, including increases in heart rate, blood volume and cardiac output (the amount of blood the heart pumps each minute). It reports that cardiac output rises by up to 50% by 20 to 24 weeks, that heart rate can rise by up to 30 beats per minute, and that by 34 weeks plasma volume is up by 40% to 50% compared with normal levels.

The same review notes that blood pressure falls from the first trimester, reaches its lowest point around 18 to 20 weeks, and then rises during the third trimester. These changes meet the needs of the mother and baby. They can also unmask previously undiagnosed heart disease or make an existing condition harder to manage. For the basic anatomy behind this, see how the heart works.

Tommy's, a UK pregnancy information service, says many people with a heart condition cope well with pregnancy, but that during pregnancy and birth the heart has to work harder than usual, so there can be risks for the woman and baby. It lists possible risks such as heart rhythm problems, heart failure and blood clots, and says the right care helps reduce them.

Rheumatic heart disease is one such cause. The World Health Organization (WHO) says that where the disease is endemic it is the principal heart disease seen in pregnant women, and that it remains prevalent in sub-Saharan Africa as well as other regions. WHO adds that it is not uncommon for women to be unaware that they have it until pregnancy, and that pregnant women with it are at risk of adverse outcomes such as arrhythmias and heart failure. The Turkish Journal review likewise says rheumatic valvular disease is a leading cause of cardiac complications in pregnant women in low-income countries. Background reading is in rheumatic heart disease, sore throats and rheumatic fever and heart valve problems.

The NHS describes pre-eclampsia as a pregnancy-related condition that causes high blood pressure. It is most likely from 20 weeks onwards, but can happen at any point in pregnancy, and the NHS notes you may not notice raised pressure yourself, which is why blood pressure and urine are checked at antenatal appointments. WHO says it affects 3 to 8% of women who give birth worldwide, and that hypertensive disorders account for around 16% of maternal deaths globally.

WHO states that early and consistent prenatal care is essential for monitoring and managing risk factors. Readers wanting the general picture of raised pressure outside pregnancy can read high blood pressure explained.

Peripartum cardiomyopathy is a weakening of the heart muscle. The Cleveland Clinic describes it as happening in the last month of pregnancy or up to five months after delivery. It is rare but can cause heart failure and can be life-threatening. The Cleveland Clinic says symptoms include fatigue, heart palpitations and shortness of breath, and that they are easy to miss because many resemble ordinary pregnancy. The Turkish Journal review calls it the leading type of cardiomyopathy seen in pregnancy.

Recovery varies. The Cleveland Clinic says that for some people the condition becomes permanent, while for others treatment can restore some or all heart function, and that anyone planning another pregnancy should discuss risk with a clinician first. The sources opened for this page did not give reliable figures for how common it is in any African country, so none are given here. Heart failure basics explains the wider condition.

Tommy's advises that anyone with a heart condition talk to their doctor before pregnancy. This appointment, sometimes called preconception counselling, can include reviewing the condition in detail, checking how well the heart is working, discussing medications, and identifying risks and ways to reduce them. It adds that a woman should be referred to a specialist team with experience in pregnancy and heart conditions, and that everyone with a heart condition will have consultant-led care. The review in the Turkish Journal also stresses preconception counselling, risk assessment and continuous monitoring.

Medicines deserve particular care. Tommy's says a team will review heart and other medicines carefully during pregnancy; some may be adjusted, changed or stopped, and others continued with monitoring. Nobody should start, stop or change a medicine on their own, because the decision depends on the condition and the stage of pregnancy. Availability of specialist services differs between countries and between regions.

Tommy's says to call the maternity unit or doctor straight away for breathlessness that stops you finishing sentences, breathlessness when lying flat or at rest, sudden or worse swelling, swelling of the face, or tiredness so great that everyday tasks become difficult. It advises calling emergency services or going to emergency care for chest pain that does not go away, or for palpitations with chest pain, breathlessness or fainting. The NHS lists a severe headache that does not go away with simple painkillers and sudden swelling of the face, hands or feet as symptoms needing immediate checking, in pregnancy or after recent birth. Emergency numbers differ by country, so use your local emergency number or maternity contact.

Pregnancy raises blood volume, heart rate and cardiac output, which most hearts handle well but which can strain a damaged valve or weakened muscle. Rheumatic heart disease, high blood pressure and pre-eclampsia, and peripartum cardiomyopathy are the main conditions covered here. Planning before pregnancy, specialist antenatal care and a clinician's review of every medicine give women with heart conditions the best chance of a safe pregnancy.