The following individuals made significant impact in the history of the unborn child in the fields of science and medicine. The links lead to their biographies on Wikipedia.
Wilhelm His: (1831-1904) Swiss anatomist pioneer of embryology. He tried to explain embryological development and he made a series of famous drawings of human embryos, the first widely published images. His work laid the foundation for future work, including that of American embryologist Franklin P. Mall.
Franklin P. Mall (1862-1917), groundbreaking embryologist who developed a famous collection of human embryo specimens collected from miscarriages. The collection was donated to the department of embryology of the Carnegie Institution (housed at Johns Hopkins University). He donated his collection to the department, and his successors continued to add to it until the description of human embryonic development was completed in the 1930s.
Ian Donald(1910-1987) British Obstetrician credited with the invention of the ultrasound in the 1950s. He was active in opposing the liberalization of Britain's abortion law in 1967, but he did not oppose abortions in "cases of necessity". I remember reading that he would give presentations about the unborn child while projecting images of ultrasound on large screens to his audience.
Kazunori Baba: Japanese inventor of the 3D ultrasound in 1984. I don't have a lot of information about him, unfortunately.
Stuart Campbell: British giant of fetal medicine, still active in the field. He popularized the use of 3D and 4D ultrasound. He was one of the first to suggest 3D ultrasound as a means of maternal bonding with the child. He also developed the procedure to aspirate ova in order to facilitate in vitro fertilization. In 2008, he called for the gestational limit of Britain's abortion law to be reduced from 24 weeks to 20 weeks, but he believed that the requirement for two doctors to sign off on 1st trimester abortions should be removed.
William Liley: (1929-1983). Deemed the father of foetology. An obstetrician from New Zealand who invented life-saving fetal blood transfusions for Rh disease. This provided the groundwork for future fetal surgery.
Although an atheist, he was a strong proponent of fetal personhood. In 1970 he founded New Zealand’s Society for the Protection of Unborn Children. He was also appointed to the Pontifical Institute of Science.
At the end of his life, he despaired that his research was used to further abortion. He became depressed and took his own life.
In 1972 he wrote a classic text called The Fetus as Personality. (More info).
Aleck Bourne: (1886-1974). British doctor who, in 1938, was tried and acquitted for having performed an abortion on a 14-year-old victim of a gang rape. The Bourne Decision effectively legalized abortion in the Commonwealth in limited circumstances. He later became a founding member of the Society for the Protection of Unborn Children and opposed Britain’s 1967 abortion law.
Michael Harrison: Considered the Father of Fetal Surgery. He operated on the first survivor of fetal surgery, Michael Skinner, in 1981, when his patient was aged 7 months gestation. Dr. Harrison is still active at the Fetal Treatment Center at the University of California at San Francisco.
Kyprios Nicolaides (1953-): The Father of Fetal Medicine. He opened Britain's first fetal medicine unit in 1984. He specializes in prenatal diagnosis. One of his most important contributions is his research on nuchal transparency to identify babies with Down Syndrome.