Sign up now Fetal development:
Sex-typed behavior[ edit ] The hormonal theory of sexuality and gender identity holds that, just as exposure to certain hormones plays a role in fetal sex differentiation, such exposure also influences the sexual orientation and or gender identity that emerges later in the adult.
Differences in brain structure that come about from chemical messengers and genes interacting on developing brain cells are believed to be the basis of sex differences in countless behaviors, including sexual orientation. As seen in young children as well as in vervet and rhesus monkeys, sexually differentiated behavior in toy preference is differing in males versus females, where females prefer dolls and males prefer toy balls and cars; these preferences can be seen as early as 3—8 months in humans.
Sketching the argument briefly here, the authors say that sexual organs are differentiated first, and then the brain is sexually differentiated "under the influence, mainly, of sex hormones such as testosterone, estrogen and progesterone on the developing brain cells and under the presence of different genes as well The changes brought about in Prenatal period stage are permanent.
Girls with CAH are born with masculinized genitalia, which is corrected surgically as soon as possible.
However, "CAH is not a perfect experiment", since, "social responses to masculinized genitalia or factors related to the disease itself" can confound results.
Children born through artificial insemination with donor sperm and consequently raised by lesbian couples have typically been heterosexually oriented.
Hypermasculinity There is evidence of a correlation between sexual orientation and traits that are determined in utero.
Fraternal birth order[ edit ] According to some studies, gay men have more older brothers on average, a phenomenon known as the fraternal birth order effect. It has been suggested that the greater the number of older male siblings the higher the level of androgen fetuses are exposed to.
No evidence of birth order effects have been observed in women. The theory holds that the fraternal birth order effect is a result of a maternal immune response that is produced towards a factor of male development over several male pregnancies.
Antimale antibodies might bind to these molecules and thus interfere with their role in normal sexual differentiation, leading some later born males to being attracted to men as opposed to women. The chance of such an immune response to male factors would increase with every pregnancy resulting in the birth of a son.
Some did not find any statistically significant difference in either the sibling composition or rate of older brothers of gay and straight men,   including large, nationally representative studies in the US and Denmark.
Other correlates to handedness e. The Rh gene hypothesis is a strong candidate because not only does it involve the maternal immune response, but it has been implicated in handedness as well.
A theory that high prenatal testosterone leads to neuronal and axonal loss in the corpus callosum is supported by this hypothesis. Hypomasculinity In a study, Simon LeVay demonstrated that a tiny clump of neurons of the anterior hypothalamus —which is believed to control sexual behavior and linked to prenatal hormones—known as the interstitial nuclei of the anterior was, on average, more than twice the size in heterosexual men when contrasted to homosexual men.
Due to this area also being nearly twice the size in heterosexual men than in heterosexual women, the implication is that the sexual differentiation of the hypothalamus in homosexuals is in a female direction.
Later studies in humans, however, have yet to confirm this finding. Together with congenital adrenal hyperplasia, DES studies have provided little support of the prenatal hormone theory of sexual orientation; they do, however, provide the framework for possible pathways to a homosexual orientation for a small number of women.
Gender dysphoria In individuals with gender dysphoriapreviously known as gender identity disorder GIDprenatal exposure to testosterone has been hypothesized to have an effect on gender identity differentiation.
The 2D;4D finger ratio, or relative lengths of the 2nd "index" and 4th "ring" fingers, has become a popular measure of prenatal androgen because of accumulated evidence suggesting the 2D;4D ratios are related to prenatal exposure to testosterone.
Adults with "late onset", or those without a childhood history of said behavior, are more likely to have a non-homosexual orientation. Transsexualism Because organ differentiation and brain differentiation occur at different times, in rare cases transsexualism can result.
Endocrine disruptors[ edit ] Endocrine disrupting chemicals EDCs are chemicals that, at certain doses, can interfere with the endocrine system in mammals. Such agents are not hormones. They should not be expected to act precisely as hormones.Pregnancy, also known as gestation, is the time during which one or more offspring develops inside a woman.
A multiple pregnancy involves more than one offspring, such as with twins. Pregnancy can occur by sexual intercourse or assisted reproductive technology. Childbirth typically occurs around 40 weeks from the last menstrual period (LMP).
This is just over nine months, where each month. Renovate Right: Important Lead Hazard Information for Families, Child Care Providers, and Schools. General information about legal requirements for safe lead practices for homeowners, tenants, child care providers and parents during renovation activities.
May 20, · Having a healthy pregnancy is one of the best ways to promote a healthy birth. Getting early and regular prenatal care improves the chances of a healthy pregnancy. This care can begin even before pregnancy with a preconception care visit to a health care provider.
A . Sep 03, · OBSTETRICS & GYNECOLOGY ASSOCIATES initiativeblog.com For Women. For Health.
For Life. The sperm and egg unite in one of your fallopian tubes to form a one-celled entity called a zygote. If more than one egg is released and fertilized or if the fertilized .
Chapter The Prenatal Period Edelman: Health Promotion Throughout the Life Span, 8th Edition. MULTIPLE CHOICE. 1. A pregnant woman reports to the nurse that the first day of her last menstrual period was January