Embryo Project Encyclopedia

The figure depicts three different molecular structures of estrogen found in mammals’ that differ by the arrangement of bonds and side groups. The molecular structures of the three estrogen molecules differ by the arrangement of chemical bonds and side groups attached to the core steroid structure, cholesterol, which contains three cyclohexane rings and one cyclopentane ring. Compared to the molecular structure of estriol, the molecular structure of estradiol is missing one oxygen-hydrogen or OH group, and estrone lacks the OH group, and one hydrogen molecule that results in a double bonded oxygen atom. These steroid hormones bind to specific cell receptor molecules and induce transcriptional changes in cells. The production of estriol increases during pregnancy, estradiol production increases during stages of the menstrual cycle, and estrone levels increase during menopause. The differing bonds and chemical arrangements enable scientists to determine the different concentrations of the molecules.

Katharina Dorothea Dalton was a physician in England in the twentieth century who defined premenstrual syndrome (PMS) as a cluster of symptoms suspected to begin one to two weeks before menstruation and disappear upon the onset of a new menstrual cycle. Prior to Dalton, there was little research on pre-menstrual issues and those that existed linked the problem to excessive water retention or estrogen. Dalton hypothesized that PMS resulted from a deficiency in the hormone progesterone and advocated for hormone replacement therapy to lessen the symptoms of the syndrome. Dalton established an early PMS clinic in London, England, and she testified on behalf of women in over fifty court cases claiming to have committed crimes while suffering from PMS.

In the early twentieth century US, Jean Paul Pratt and Edgar Allen conducted clinical experiments on women who had abnormal menstrual cycles. During the clinical tests, researchers injected the hormone estrogen into their patients to alleviate their menstrual ailments, which ranged from irregular cycles to natural menopause. The hormone estrogen plays a prominent role in the menstrual cycle by signaling the tissue lining the uterus (endometrium) to thicken in preparation for possible pregnancy. In their clinical tests, Pratt and Allen showed that injecting estrogen into female human subjects restored their normal menstrual cycle, removed symptoms such as hot flashes, and caused uterine tissue to grow. The clinical tests conducted by Pratt and Allen provided experimental evidence and justification for the injection of isolated estrogen in women to alleviate, for a short amount of time, different menstrual problems, and it contributed to later hormone therapy research.

Polycystic ovarian syndrome or PCOS is one of the most common reproductive conditions in women, and its symptoms include cystic ovaries, menstrual irregularities, and elevated androgen or male sex hormone levels. During the 1930s, Irving Freiler Stein and Michael Leventhal identified the syndrome and its symptoms. Women who experience symptoms of PCOS may also experience secondary symptoms, including infertility and diabetes. Though estimates vary and the causes of the syndrome are not clear as of 2017, PCOS affects approximately ten percent of women of reproductive age. Women who suspect they have symptoms of PCOS should see a doctor, as early treatment may help prevent long-term implications such as infertility, diabetes, and some types of cancers.

The article Experimental Studies on Congenital Malformations was published in the Journal of Chronic Diseases in 1959. The author, James G. Wilson, studied embryos and birth defects at the University of Florida Medical School in Gainesville, Florida. In his article, Wilson reviewed experiments on birds and mammals from the previous forty years to provide general principles and guidelines in the study of birth defects and teratogens, which are things that cause birth defects. Those principles included what species are convenient for conducting teratological research, what principles act in human embryological and fetal development, and what agents impact those processes. Wilson's article was one of the first attempts in the twentieth century to synthesize basic research conducted in the field of teratology. The article helped to establish teratology as a field in medicine during the twentieth century.

George Nicholas Papanicolaou developed the Pap test in the United States during the twentieth century. The Pap test is a diagnostic procedure used to test for cervical cancer in women. Papanicolaou’s work helped improve the reproductive health of women by providing an effective means of identifying precancerous cells and improving the likelihood of early treatment and survival of cervical cancer.

In June 2017, the Iowa Supreme Court decided the case Plowman v. Fort Madison Community Hospital, or Plowman v. FMCH, and ruled that women who gave birth to children with severe disabilities could sue for wrongful birth in Iowa. Specifically, after Plowman v. FMCH, a woman could sue for wrongful birth if she believed that her physicians failed to disclose evidence of fetal abnormalities that may have prompted her to terminate the pregnancy. Pamela and Jeremy Plowman filed the suit against the Fort Madison Community Hospital in Fort Madison, Iowa, alleging that hospital physicians failed to inform them that a prenatal test showed fetal abnormalities. Plowman v. FMCH gave women in Iowa the legal right to sue if physicians failed to tell them about fetal defects.

Thalidomide is a sedative drug introduced to European markets on 1 October 1957 after extensive testing on rodent embryos to ensure its safety. Early laboratory tests in rodent populations showed that pregnant rodents could safely use it, so doctors prescribed Thalidomide to treat morning sickness in pregnant women. However, in humans Thalidomide interfered with embryonic and fetal development in ways not observed in rodent tests. Pregnant women who take Thalidomide are at grater than normal risk for spontaneous abortion and for giving birth to children with developmental anomalies such as shortened, absent, or extra limbs, as well as a variety of heart, ear, and internal organ defects. The failure of rodent models to inform scientists of Thalidomide's teratogenicity in humans ignited debate about the proper use of cross-species testing during drug development.

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.