Since the 1950s, scientists have developed interspecies blastocysts in laboratory settings, but not until the 1990s did proposals emerge to engineer interspecies blastocysts that contained human genetic or cellular material. Even if these embryos were not permitted to mature to fetal stages, their ethical and political status became debated within nations attempting to use them for research. To study cell differentiation and embryonic development and causes of human diseases, interspecies-somatic-cell-nuclear-transfer -derived (iSCNT) humanesque blastocysts provided opportunities for research and therapy development. Such a technology also involved ethical debates.

Turtle morphology is unlike that of any other vertebrate. The uniqueness of the turtle's bodyplan is attributed to the manner in which the turtle's ribs are ensnared within its hard upper shell. The exact embryological and genetic mechanisms underpinning this peculiar anatomical structure are still a matter of debate, but biologists agree that the evolution of the turtle shell lies in the embryonic development of the turtle.

Two main elements characterize the skeletal morphology of turtles: the carapace and the plastron. For a turtle, the carapacial ridge begins in the embryo as a bulge posterior to the limbs but on both sides of the body. Such outgrowths are the first indication of shell development in turtle embryos. While the exact mechanisms underpinning the formation of the carapacial ridge are still not entirely known, some biologists argue that understanding these embryonic mechanisms is pivotal to explaining both the development of turtles and their evolutionary history.

Methylmercury (MeHg) is an organic form of mercury that can damage the developing brains of human fetuses. Women who consume methylmercury during pregnancy can bear children who have neurological issues because methylmercury has toxic effects on the nervous system during embryonic development. During the third week of gestation, the human nervous system begins to form in the embryo. During this gestational period, the embryo's nervous system is particularly susceptible to the influence of neurotoxins like methylmercury that can result in abnormalities. Furthermore, the fetal brain can incur damage despite the lack of signs of poisoning in the pregnant woman. In children, defects due to methylmercury can result in deficits in attention, behavior, cognition, and motor skills.

The hedgehog signaling pathway is a mechanism that regulates cell growth and differentiation during embryonic development, called embryogenesis, in animals. The hedgehog signaling pathway works both between cells and within individual cells.

Estrogen is the primary sex hormone in women and it functions during the reproductive menstrual cycle. Women have three major types of estrogen: estrone, estradiol, and estriol, which bind to and activate receptors within the body. Researchers discovered the three types of estrogen over a period of seven years, contributing to more detailed descriptions of the menstrual cycle. Each type of estrogen molecule contains a slightly different arrangement or number of atoms that in turn causes some of the estrogens to be more active than others. The different types of estrogen peak and wane throughout women's reproductive cycles, from normal menstruation to pregnancy to the cessation of menstruation (menopause). As scientists better explained the effects of estrogens, they used that information to develop oral contraceptives to control pregnancy, to map the menstrual cycle, and to create hormone therapies to regulate abnormal levels of estrogen.

The use of blood in forensic analysis is a method for identifying individuals suspected of committing some kinds of crimes. Paul Uhlenhuth and Karl Landsteiner, two scientists working separately in Germany in the early twentieth century, showed that there are differences in blood between individuals. Uhlenhuth developed a technique to identify the existence of antibodies, and Landsteiner and his students showed that humans had distinctly different blood types called A, B, AB, and O. Once doctors differentiated blood into distinct types, they could use that information to safely perform blood transfusions. Furthermore, forensic scientists could use that information to exculpate people suspected of some types of crimes, and they could use it to help determine the paternity of children.

Between 1925 and 1961, a Roman Catholic order of nuns called the Bon Secours Sisters operated the Bon Secours Mother and Baby Home, or the Home, an institution where unmarried pregnant women gave birth in Tuam, Ireland. Pregnant women who delivered their infants at the Home were required to work at the Home for no less than one year without pay. The Irish government and the Catholic Church endorsed the Mother and Baby Home as a means to limit the number of children born out of wedlock by discouraging women from getting pregnant before marriage. During the Home’s thirty-six years of operation, the nuns reported that almost 800 children died in their care. In 2015, researchers discovered a tomb of 796 infant and child skeletons in a septic tank underneath where the Home once stood. The acceptance and use of Mother and Baby Homes revealed the way Ireland treated pregnant women in the twentieth century.

Hydrocephalus is a congenital or acquired disorder characterized by the abnormal accumulation of cerebrospinal fluid within the cavities of the brain, called ventricles. The accumulation of cerebrospinal fluid, the clear fluid surrounding the brain and spinal cord, causes an abnormal widening of the ventricles. The widening creates potentially harmful pressure on the tissues of the brain that can result in brain damage or death. The most obvious sign of hydrocephalus is the rapid increase in head circumference or an unusual large head size due to the accumulation of cerebrospinal fluid in the brain. In infants, hydrocephalus can be caused by congenital factors such as malformations of the brain, or acquired factors such as tumors, cysts, meningitis, or bleeding. Treatment after the infant is born can lead to normal cognitive and physical development with few limitations.

Sprayed extensively by the US military in Vietnam, Agent Orange contained a dioxin contaminant later found to be toxic to humans. Despite reports by Vietnamese citizens and Vietnam War veterans of increased rates of stillbirths and birth defects in their children, studies in the 1980s showed conflicting evidence for an association between the two. In 1996, the US National Academy of Sciences reported that there was evidence that suggested dioxin and Agent Orange exposure caused spina bifida, a birth defect in which the spinal cord develops improperly. The US Department of Veterans Affairs' subsequent provision of disability compensation for spina bifida-affected children marked the US government's first official acknowledgement of a link between Agent Orange and birth defects. By 2016, spina bifida and related neural tube defects were the only birth defects associated with Agent Orange.