Human fetal tissue is currently defined in the U.S. Code (42 U.S.C. 289g–1(g)) as the resulting “tissue or cells obtained from a dead human embryo or fetus after a spontaneous or induced abortion, or after a stillbirth.” To further break down this definition, “embryo” refers to the first stages of fetal development, from fertilized egg through the 10th week of pregnancy. At the 9th week, the embryo technically becomes a fetus. A spontaneous abortion is a naturally occurring loss of a pregnancy that takes place before the 20th week. A spontaneous abortion is also referred to as a “miscarriage.” This is usually distinguished from a stillbirth, which refers to the loss of a fetus that takes place between the 20th week of pregnancy and birth. It is important to note that HR 1203 uses the term “stillbirth” broadly to refer to a natural loss of pregnancy at any stage of development, embryonic or fetal.
According to a report from the Congressional Research Service, the majority of human fetal tissue that is useful for scientific and medical research is derived from induced abortions. This is largely due to the fact that human tissue can deteriorate rapidly postmortem unless properly preserved, which requires preparation and consent from the mother. Thus, the unplanned nature of spontaneous abortions and stillbirths make them much less conducive for fetal tissue donation.
Human fetal tissue is particularly beneficial for scientific and medical research and is often used to establish cell lines or for transplantation into other organisms. The fetus undergoes rapid development of organs and tissues during the first 14 weeks of pregnancy, when the vast majority of abortions take place. Cells derived from fetal tissues at these stages are valuable in that they have already started to differentiate into organs (such as the fetal liver, thymus, eye, and nervous system) but still retain renewable stem cell potential, enabling them to grow and divide rapidly and adapt to new environments once extracted.
Cell lines from these fetal tissues can be used to conduct tissue- or organ-specific studies on human development or diseases. Fetal tissue can also be used to develop humanized animals (i.e., human-animal hybrids) in order to study human tissues in a living environment or to produce human or human-like organs for transplantation. Alternatively, fetal tissue cells can be directly implanted into patients as a therapy, such as the landmark study conducted in 1987, in which fetal brain tissue was transplanted into patients with Parkinson’s disease.
Via these applications, human fetal tissue has been instrumental in the development of vaccinations for polio, chickenpox, rubella, measles, rabies, tetanus, whooping cough, and more. In 2015 alone, the National Institutes of Health granted around $80 million in funding for medical research involving human fetal tissue. These studies investigated HIV, retinal degeneration, lupus, hepatitis, typhoid, diabetes, sudden infant death syndrome, and other serious health conditions.