老牛亲过。没算时间。但肯定不止半小时。没准有一小时。看来人生完整啊。
从来不理解亲嘴有啥快感？
版主： kazaawang， wh
怎么能亲那么长啊…… 
#84 Re: 从来不理解亲嘴有啥快感？
还真的有科学依据！不过又说被近年的研究推翻了，新研究认为姿势和深度与婴儿性别无关。不知道哪个更科学……
Sex positions when trying for a baby girl: What does the science say?
... Shettles recommended that the best sex positions to conceive a girl are those where penetration isn’t very deep.
Shallow penetration will more likely result in a baby girl, the theory goes, because the sperm has to live longer to fertilize the egg. To do that, it needs to survive the acidic environment of the vagina, which favors the X chromosome sperm.
On that basis, face-to-face positions are ideal for conceiving a baby girl, with old-fashioned missionary the best option. Deep penetration — for example, from behind — makes Y chromosome sperm more likely to fertilize an egg, because they're ejaculated closer to the cervix where it's less acidic and more alkaline.
But, more recent research has refuted the basis of Shettles’s claims. In 2020, scientists in South Korea reviewed a bunch of studies from as far back as the 1950s that looked into the characteristics of male (Y) and female (X) sperm. They concluded that any difference between them is limited to the content of their DNA.
In other words, there’s no evidence that X chromosome and Y chromosome sperm differ in shape, size, or speed, nor in how they respond to the pH of their environment. So, sexual position has no bearing on which is more likely to fertilize an egg.
A similar idea is that sex with the female partner on top can increase the chances of conceiving a girl, because you can control the depth of penetration. But it’s also been suggested that “girl on top” makes it less likely you’ll get pregnant at all, because gravity is working against you.
However, Twogood points out that sex position makes absolutely no difference to conception of a baby girl or a baby boy. “Sperm don’t use gravity to help or hinder them,” she says. “No matter the position, when sperm is released inside the vagina, it’s close to the cervix. Within just a few minutes, sperm can travel through the female reproductive system to the tubes.”
