Gordon Watkins Douglas researched cervical cancer, breach delivery, and treatment of high blood pressure during pregnancy in the US during the twentieth century. He worked primarily at Bellevue Hospital Center in New York, New York. While at Bellevue, he worked with William E. Studdiford to develop treatments for women who contracted infections as a result of illegal abortions performed throughout the US in unsterile environments. Douglas also established the first contraception and pregnancy termination clinic at Bellevue Hospital shortly after the legalization of abortion as a result of the 1973 US Supreme Court ruling in Roe v. Wade. Furthermore, Douglas showed that fetal and maternal cells exchange between the pregnant woman and fetus during pregnancy, which led to the later development of non-invasive prenatal testing in the early twenty-first century.

In 2004, a team of researchers at Tufts-New England Medical Center in Boston, Massachusetts, investigated the fetal cells that remained in the maternal blood stream after pregnancy. The results were published in Transfer of Fetal Cells with Multilineage Potential to Maternal Tissue. The team working on that research included Kiarash Khosrotehrani, Kirby L. Johnson, Dong Hyun Cha, Robert N. Salomon, and Diana W. Bianchi. The researchers reported that the fetal cells passed to a pregnant woman during pregnancy could develop into multiple cell types in her organs. They studied these differentiated fetal cells in a cohort of women fighting different diseases. The researchers found that the fetal cells in the women differentiated into different cell types under the influence of maternal tissues, and that those differentiated cells concentrated in the tissue surrounding diseased tissues. According to the team, this response could be a therapeutic response to the disease in the once pregnant woman. The research indicated the long lasting effects of pregnancy in a woman's body.