Anencephaly is an open neural tube defect, meaning that part of the neural tube does not properly close or that it has reopened during early embryogenesis. An embryo with anencephaly develops without the top of the skull, but retains a partial skull, including the face.

Isotretinoin is a molecule and a byproduct (metabolite) of vitamin A, and in greater than normal amounts in pregnant women, it can cause fetal abnormalities including cleft lips, ear and eye defects, and mental retardation. Isotretinoin is commonly called by its trade name Accutane, and it's a chemical compound derived from vitamin A, also called retinoic acid.

Josef Warkany studied the environmental causes of birth defects in the United States in the twentieth century. Warkany was one of the first researchers to show that factors in the environment could cause birth defects, and he helped to develop guidelines for the field of

In 1984, J. David Erickson and his research team published the results of a study titled "Vietnam Veterans' Risks for Fathering Babies with Birth Defects" that indicated that Vietnam veterans were at increased risk of fathering infants with serious congenital

Virginia Apgar worked as an obstetrical anesthesiologist, administering drugs that reduce women's pain during childbirth, in the mid-twentieth century US. In 1953, Apgar created a scoring system using five easily assessable measurements, including heart rate and breathing rate, to evaluate whether or not infants would benefit from medical attention immediately after birth. Apgar's system showed that infants who were previously set aside as too sick to survive,

Sidney Q. Cohlan studied birth defects in the US during the twentieth century. Cohlan helped to discover that if a pregnant woman ate too much vitamin A her fetus faced a higher than normal risk of teratogenic effects, such as cleft palate. A teratogen is a substance that causes malformation of a developing organism. Cohlan

Spina bifida is a birth defect that affects the spines of developing fetuses and infants, and research in the 20th century indicated that chemicals in the herbicide Agent Orange likely led to the birth defect. People with spina bifida can have nerve damage, paralysis, and mental disabilities. During the Vietnam War in the 1960s, the US military employed Agent Orange and other herbicides to

Editor's Note: This article replaces the previous article on this topic, which was published in this encyclopedia in 2012. The 2012 article may be found at http://hdl.handle.net/10776/4202.

In March 1996, the National Academy of Sciences of the United States released "Veterans and Agent Orange Update 1996: Summary and Research Highlights," which summarized research on the health