Fetal Heart Development

Nothing is as terrifying as finding out that all is not right with the most important organ your baby has. Angela Thomas from Englewood Cliffs, New Jersey, remembers that feeling all too well. Last year she gave birth to her daughter, Maia, knowing that her daughter had a serious heart problem. "The problem was detected at the 5-month ultrasound check," Thomas says. "Needless to say, we went through a tailspin especially where doctors mentioned the termination word. Something kept telling me not to terminate and I was vigilant for the remaining months with meditation and outstanding medical care. It was surreal but with faith and wonderful guidance at Columbia Medical University, Maia is doing incredible."

Maia was born with a hole in the heart, and she had to have one of her valves detached and re-routed. Thomson's vigilance and care was rewarded. After Maia was delivered, she went right into a very successful surgery."I would like other mothers to know there are good stories that exist, and the utmost thing for a mom to do is to remain positive and enjoy her pregnancy and delivery," Thomson says.

Heart Formation

Dr. Gail Pearson, a board certified pediatric cardiologist with the National Heart, Lung, and Blood Institute, says the heart develops very early in the fetus' development. "The heart is among the earliest organs to develop, and a primitive version is already beating and pumping blood to the developing fetus by 7 weeks' gestation," Dr. Pearson says. "The early rapid growth of the embryo requires a system of nutrient delivery beyond simple diffusion from one cell to another, so the early development of the heart and blood vessels is a key step."

The formation of an infant's heart begins as a simple tube, which over the next few weeks becomes a four-chambered heart with outflow tracks and venous return. "The heart develops from specialized cells in at least two parts of the early embryo," Dr. Pearson says. "These cells coalesce to become a primitive heart tube, which then expands in certain areas and undergoes a process known as looping to arrive at the final heart structure."

The heart's development can be affected at any point in this process by things that affect how cells signal to each other, how they migrate during development and how they divide and grow, Dr. Pearson says.

Factors Affecting Heart Development

Dr. Pearson says that although scientists are still learning about factors that control normal heart development and specific causes of congenital heart malformations, they have found that the following contribute to problems with heart development:

• Chromosomal abnormalities: For example, Trisomy 21, the chromosomalabnormality associated with Down syndrome, is associated with cardiac abnormalities in 50 percent of babies.
• Other genetic abnormalities: A single gene can develop abnormally and this canbe associated with the development of a congenital heart defect.
• Maternal diseases such as diabetes: Poor blood sugar control in a mother with diabetes is known to be associated with increased risk of heart defects in the baby.
• Maternal infections like rubella (German measles): Fortunately, German measles is now very rare, but obstetricians always check to be sure a mother is protected against German measles at the beginning of a pregnancy.
• Drugs or substances taken by the mother: Dilantin (used to treat seizures), cocaine, alcohol, and Accutane (used to treat acne) can all affect fetal heart formation.
• Exposure to certain substances in the environment: Paints, solvents,degreasers, pesticides; air pollutants such as trichloroethylene; and possibly radiation are all things to be avoided.