Many babies born with atrial septal defects don't have associated signs or symptoms. In adults, signs or symptoms may begin around age 30, but in some cases signs and symptoms may not occur until decades later.

Atrial septal defect signs and symptoms may include:

• Shortness of breath, especially when exercising
• Fatigue
• Swelling of legs, feet or abdomen
• Heart palpitations or skipped beats
• Stroke
• Heart murmur, a whooshing sound that can be heard through a stethoscope

Why do heart defects develop?

Doctors know that heart defects present at birth (congenital) arise from errors early in the heart's development, but there's often no clear cause. Genetics and environmental factors may play a role.

Heart works with an atrial septal defect

An atrial septal defect (ASD) allows freshly oxygenated blood to flow from the left upper chamber of the heart (left atrium) into the right upper chamber of the heart (right atrium). There, it mixes with deoxygenated blood and is pumped to the lungs, even though it's already refreshed with oxygen.

If the atrial septal defect is large, this extra blood volume can overfill the lungs and overwork the right side of the heart. If not treated, the right side of the heart eventually enlarges and weakens. If this process continues, the blood pressure in your lungs may increase as well, leading to pulmonary hypertension.

Atrial septal defects can be several types, including:

• Secundum. This is the most common type of ASD, and occurs in the middle of the wall between the atria (atrial septum).
• Primum. This defect occurs in the lower part of the atrial septum, and may occur with other congenital heart problems.
• Sinus venosus. This rare defect usually occurs in the upper part of the atrial septum.
• Coronary sinus. In this rare defect, part of the wall between the coronary sinus — which is part of the vein system of the heart — and the left atrium is missing.

It's not known why atrial septal defects occur, but congenital heart defects appear to run in families and sometimes occur with other genetic problems, such as Down syndrome. If you have a heart defect, or you have a child with a heart defect, a genetic counselor can estimate the odds that any future children will have one.

Some conditions that you have or that occur during pregnancy may increase your risk of having a baby with a heart defect, including:

• Rubella infection. Becoming infected with rubella (German measles) during the first few months of your pregnancy can increase the risk of fetal heart defects.
• Drug, tobacco or alcohol use, or exposure to certain substances. Use of certain medications, tobacco, alcohol or drugs, such as cocaine, during pregnancy can harm the developing fetus.
• Diabetes or lupus. If you have diabetes or lupus, you may be more likely to have a baby with a heart defect.
• Obesity. Being extremely overweight (obese) may play a role in increasing the risk of having a baby with a birth defect.
• Phenylketonuria (PKU). If you have PKU and aren't following your PKU meal plan, you may be more likely to have a baby with a heart defect.

A small atrial septal defect may never cause any problems. Small atrial septal defects often close during infancy.

Larger defects can cause serious problems, including:

• Right-sided heart failure
• Heart rhythm abnormalities (arrhythmias)
• Increased risk of a stroke
• Shortened life span

  Less common serious complications may include:

• Pulmonary hypertension. If a large atrial septal defect goes untreated, increased blood flow to your lungs increases the blood pressure in the lung arteries (pulmonary hypertension).
• Eisenmenger syndrome. Pulmonary hypertension can cause permanent lung damage. This complication, called Eisenmenger syndrome, usually develops over many years and occurs uncommonly in people with large atrial septal defects.

• Treatment can prevent or help manage many of these complications.

  Atrial septal defect and pregnancy

  Most women with an atrial septal defect can tolerate pregnancy without any problems. However, having a larger defect or having complications such as heart failure, arrhythmias or pulmonary hypertension can increase your risk of complications during pregnancy. Doctors strongly advise women with Eisenmenger syndrome not to become pregnant because it can endanger their lives.

  The risk of congenital heart disease is higher for children of parents with congenital heart disease, whether in the father or the mother. Anyone with a congenital heart defect, repaired or not, who is considering starting a family should carefully discuss it beforehand with a doctor. Some medications may need to be stopped or adjusted before you become pregnant because they can cause serious problems for a developing fetus.