There are specific times during a baby’s development when a certain body part is especially vulnerable to damage from harmful substances and exposures. These substances can include alcohol, medications, and cigarette smoking. The chart below shows these critical periods. If something interferes or disrupts development during these times, the result may be a birth defect.
*Image courtesy of NOFAS.
The dark blue segments on the picture above show when certain body parts are most at risk for major birth defects. Major birth defects cause significant medical problems and may require surgery or other treatment. Some examples of major birth defects include heart defects and spina bifida.
The light blue sections of the chart show periods when fetal development is susceptible to minor birth defects and functional defects. Minor birth defects do not cause significant problems and usually do not require medical intervention, such as treatment or surgery. Minor birth defects include things like the shape of the ears or certain facial features. Functional defects affect how a part of the body works. For example, hearing loss can be a functional defect.
Timing of exposures
According to MotherToBaby, “Harmful exposures during the first trimester have the greatest risk of causing major birth defects. This is because of the many, important developmental changes that take place during this time. The major structures of the body form in the first trimester. These include the spine, head, arms and legs. The baby’s organs also begin to develop. Some examples of these organs are the heart, intestines and lungs.”
While exposures during the first trimester do pose the greatest risk of birth defects, exposures during the second and third trimester can cause problems with growth as well as minor birth defects. Factors that affect growth can put babies at risk for other health problems.
The brain continues to develop throughout pregnancy, after the baby is born, and into young adulthood. Harmful substances and exposures during the second and third trimester can cause developmental delays and learning disabilities.
Planning for pregnancy is important
Looking at the chart above, it is easy to see why preconception care is so important. Crucial fetal development happens very early in pregnancy– in many cases, before a woman even knows that she is pregnant. Seeing your health care provider BEFORE pregnancy and discussing any medications you are taking and underlying medical conditions, like diabetes or high blood pressure, can help you be better prepared for pregnancy and to reduce your risk of birth defects.
*We would like to thank the National Organization on Fetal Alcohol Syndrome (NOFAS) for allowing us to use their fetal development chart. Please visit their website for more important information about fetal alcohol spectrum disorders.
Have questions? Email us at AskUs@marchofdimes.org.