Intrauterine device insertions: which variables matter?

Objectives: Many factors are suspected to influence the intrauterine device (IUD) insertion process. This study sought to examine the effects of a few key variables on IUD insertion tolerability, complications and follow-up issues.

Methods: A retrospective chart review was undertaken of all IUD insertions over an 11-month period at an urban Canadian women's clinic.

Masculinized finger length patterns in human males and females with congenital adrenal hyperplasia.

The ratio of the length of the second digit (2D) to the length of the fourth digit (4D) is greater in women than in men. Since androgens are involved in most somatic sex differences and since the sexual dimorphism in 2D:4D is stable from 2 years of age in humans, it was hypothesized that finger length pattern development might be affected by early androgen exposure. Human females with congenital adrenal hyperplasia (CAH) are exposed prenatally to higher than normal levels of adrenal androgens, providing an opportunity to test the effects of early androgen exposure on digit ratios.

Sexual dimorphism in digit-length ratios of laboratory mice.

The lengths of the index finger (2D) and ring finger (4D) are sexually dimorphic in humans, and men have a smaller 2D:4D ratio compared to women. Prenatal androgens appear to be important in the development of the 2D:4D sex difference, since it has been reported in children as young as 2 years old, and since humans exposed to supernormal prenatal androgen levels display a smaller 2D:4D ratio. We tested whether another mammalian species in which the process of peripheral sexual differentiation is androgen-dependent might also show a sex difference in digit ratios.

Differences in finger length ratios between self-identified "butch" and "femme" lesbians.

There is indirect evidence that heightened exposure to early androgen may increase the probability that a girl will develop a homosexual orientation in adulthood. One such putative marker of early androgen exposure is the ratio of the length of the index finger (2D) to the ring finger (4D), which is smaller in male humans than in females, and is smaller in lesbians than in heterosexual women. Yet there is also evidence that women may have different sexual orientations at different times in their lives, which suggests that other influences on female sexual orientation, presumably social, are at work as well.