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Your immune system is a complex network of cells, tissues, and organs. Together they help the body fight infections and other diseases.

When germs such as bacteria or viruses invade your body, they attack and multiply. This is called an infection. The infection causes the disease that makes you sick. Your immune system protects you from the disease by fighting off the germs.

The immune system has many different parts, including:

• Your skin, which can help prevent germs from getting into the body
• Mucous membranes, which are the moist, inner linings of some organs and body cavities. They make mucus and other substances which can trap and fight germs.
• White blood cells, which fight germs
• Organs and tissues of the lymph system, such as the thymus, spleen, tonsils, lymph nodes, lymph vessels, and bone marrow. They produce, store, and carry white blood cells.

Your immune system defends your body against substances it sees as harmful or foreign. These substances are called antigens. They may be germs such as bacteria and viruses. They might be chemicals or toxins. They could also be cells that are damaged from things like cancer or sunburn.

When your immune system recognizes an antigen, it attacks it. This is called an immune response. Part of this response is to make antibodies. Antibodies are proteins that work to attack, weaken, and destroy antigens. Your body also makes other cells to fight the antigen.

Afterwards, your immune system remembers the antigen. If it sees the antigen again, it can recognize it. It will quickly send out the right antibodies, so in most cases, you don't get sick. This protection against a certain disease is called immunity.

There are three different types of immunity:

• Innate immunity is the protection that you are born with. It is your body's first line of defense. It includes barriers such as the skin and mucous membranes. They keep harmful substances from entering the body. It also includes some cells and chemicals which can attack foreign substances.
• Active immunity, also called adaptive immunity, develops when you are infected with or vaccinated against a foreign substance. Active immunity is usually long-lasting. For many diseases, it can last your entire life.
• Passive immunity happens when you receive antibodies to a disease instead of making them through your own immune system. For example, newborn babies have antibodies from their mothers. People can also get passive immunity through blood products that contain antibodies. This kind of immunity gives you protection right away. But it only lasts a few weeks or months.

Sometimes a person may have an immune response even though there is no real threat. This can lead to problems such as allergies, asthma, and autoimmune diseases. If you have an autoimmune disease, your immune system attacks healthy cells in your body by mistake.

Other immune system problems happen when your immune system does not work correctly. These problems include immunodeficiency diseases. If you have an immunodeficiency disease, you get sick more often. Your infections may last longer and can be more serious and harder to treat. They are often genetic disorders.

There are other diseases that can affect your immune system. For example, HIV is a virus that harms your immune system by destroying your white blood cells. If HIV is not treated, it can lead to AIDS (acquired immunodeficiency syndrome). People with AIDS have badly damaged immune systems. They get an increasing number of severe illnesses.

Cleft lip and cleft palate are birth defects that occur when a baby's lip or mouth do not form properly. They happen early during pregnancy. A baby can have a cleft lip, a cleft palate, or both.

A cleft lip happens if the tissue that makes up the lip does not join completely before birth. This causes an opening in the upper lip. The opening can be a small slit or a large opening that goes through the lip into the nose. It can be on one or both sides of the lip or, rarely, in the middle of the lip.

Children with a cleft lip also can have a cleft palate. The roof of the mouth is called the "palate." With a cleft palate, the tissue that makes up the roof of the mouth does not join correctly. Babies may have both the front and back parts of the palate open, or they may have only one part open.

Children with a cleft lip or a cleft palate often have problems with feeding and talking. They also might have ear infections, hearing loss, and problems with their teeth.

Often, surgery can close the lip and palate. Cleft lip surgery is usually done before age 12 months, and cleft palate surgery is done before 18 months. Many children have other complications. They may need additional surgeries, dental and orthodontic care, and speech therapy as they get older. With treatment, most children with clefts do well and lead a healthy life.

Centers for Disease Control and Prevention

Congenital heart defects (CHDs) are problems with the structure of the heart. "Congenital" means that that the problems are present at birth. These defects happen when a baby's heart doesn't develop normally during pregnancy. Congenital heart defects are the most common type of birth defect.

Congenital heart defects can change the way the heart pumps blood. They may make blood flow too slowly, go the wrong way, or block it completely.

There are many types of congenital heart defects. They can happen in one or more parts of the heart. The most common types are:

• Septal defects ("hole in the heart") - openings in the wall between the left and right sides of the heart
• Heart valve defects - problems with the valves that control the flow of blood through the heart
• Defects in the large blood vessels that carry blood in and out of the heart

Congenital heart defects can range from very mild problems that never need treatment to life-threatening problems at birth. The most serious congenital heart defects are called critical congenital heart disease. Babies with these defects usually need surgery in the first year of life. But the symptoms of milder heart defects may not show up until childhood or adulthood.

Researchers often don't know what causes congenital heart defects. They do know that changes in a baby's genes sometimes cause a heart defect. The changed genes may come from the parents, or the changes may happen during pregnancy.

Several things may increase the chance that your baby has a congenital heart defect, such as:

• Your health before and during pregnancy, including
  • Having diabetes before pregnancy or developing it in the first 3 months of pregnancy (diabetes that develops later in pregnancy isn't a major risk for heart defects). Carefully controlling your blood sugar before and during pregnancy can lower your baby's risk of congenital heart defects.
  • Having phenylketonuria (PKU), a rare inherited disorder that affects how the body uses a protein in foods. If you have PKU, eating a low-protein diet before getting pregnant can lower your baby's risk of having a congenital heart defect.
  • Having rubella (German measles) during pregnancy.
• Your contact with certain substances during pregnancy, including
  • Smoking or secondhand smoke (breathing smoke from another smoker).
  • Certain medicines, such as angiotensin-converting (ACE) inhibitors for high blood pressure and retinoic acids for acne. If you're pregnant or plan to get pregnant, talk with your health care provider about all the medicines you take.
• Your family history and genetics. In most cases, congenital heart defects don't run in families. But your chance of having a baby with a congenital heart defect does go up if you or the other parent has a congenital heart defect, or if you already have a child with a congenital heart defect.

Congenital heart defects don't cause pain. The signs and symptoms are different, depending on the type and number of defects and how serious they are.

Common signs and symptoms of congenital heart defects include:

• Cyanosis - a bluish color to the skin, lips, and fingernails. It happens when there isn't enough oxygen in the blood
• Fatigue - your baby may be unusually sleepy and may become very tired during feedings
• Poor blood flow
• Fast or difficult breathing
• Heart murmur - an unusual sound between heartbeats

Congenital heart defects don't always cause other problems. If they do, which problems you have would depend on the type and number of defects and how serious the defects are.

Children with congenital heart defects are more likely to:

• Be smaller than other children
• Have problems or delays in mental, and emotional growth, and behavior, such as:
  • Speech and language problems
  • Attention deficit hyperactivity disorders (ADHD)

People with congenital heart defects may develop other health conditions, including:

• Endocarditis - an infection of lining of the heart and valves
• Arrhythmia - a problem with the rate or rhythm of your heartbeat
• Heart failure - when your heart can't pump enough blood to the body
• Pulmonary hypertension - high blood pressure in your lungs
• Kidney and liver disease

• Before a baby is born, your provider may use ultrasound pictures of the baby's heart to look for heart defects. This is called a fetal echocardiogram. It's done between weeks 18 and 22 of pregnancy.
• During the first few days after birth, all newborns are checked for congenital heart defects. A pulse oximeter is clipped to your baby's hands or feet to measure blood oxygen. If it shows low levels of blood oxygen, more tests will be needed to find out if your baby has a heart defect.
• To diagnose congenital heart defects in babies, children, and adults, a provider may use many tools, including:
  • A physical exam.
  • Certain heart tests to see how the heart is working.
  • Genetic testing to see if certain gene problems caused the defect.

Treatment depends on the type of congenital heart defect and how serious it is. Possible treatments include:

• Cardiac catheterization to repair simple defects, such as a small hole in the inside wall of the heart. A catheterization uses a thin tube guided through a vein and into the heart.
• Heart surgery may be needed to:
  • Repair defects in the heart and blood vessels.
  • Repair or replace a heart valve.
  • Place a device in the chest to help the heart pump blood.
  • Do a heart transplant.
• Medicine is often used if your baby has a specific type of congenital heart defect called patent ductus arteriosus.

All children and adults who have congenital heart defects need regular follow-up care from a cardiologist (a doctor who specializes in heart diseases) throughout their life, even if their defect was repaired.

Some people may need several heart surgeries or catheterizations over the years. They may also need to take medicines to help their hearts work as well as possible.

NIH: National Heart, Lung, and Blood Institute