One of the questions that comes up on the boards all the time is "does swaying work?" These are my thoughts on the subject.
I've read the studies in the FAQ, I've read other information available here and elsewhere online, I've followed information about people's sways, and I've even done my own extensive research into one aspect of swaying (timing). My feeling is that swaying absolutely does "work" (in the sense that it increases your odds of a particular gender). I've seen lots of evidence that various things influence the gender ratio, and I think logically it makes sense that various environmental factors could influence gender.
I do think our knowledge of swaying is incomplete. There isn't a whole lot of research available, and so we don't really know how much various factors sway (does it sway 10%? 5%? 2%?), we may be unaware of some factors that sway, and we might even be wrong about the way certain factors sway. With incomplete information, there is some disagreement about how various factors sway. Some people think the moon sways; others of us are extremely skeptical that it has any influence at all. Some people think frequent BD through ovulation is a great girl swaying method; I think if it sways at all, it sways for boys. Still, despite our incomplete knowledge about swaying, I do believe we have identified a number of things that can influence the gender ratio.
However, I don't really think that swaying is all that effective. The most optimistic odds I have seen anyone give for a perfect sway is 75-80% effective. (The odds might be higher with extreme gender swaying, but since we have so few examples of people who have tried it, it's hard to know for sure.) People with near perfect sways are often stunned when they get an opposite and decide swaying doesn't work. People who see near perfect sways fail have their "faith" in swaying shaken. Personally, I agree with the 75-80% effectiveness rate for a near perfect sway. However, I guess I am different from most people in that I don't see 75-80% as being very good odds.
Look at it this way. The "normal" odds for gender are 50/50. So if you have 4 women who don't sway, 2 should end up with girls (or boys). In contrast, the odds for a near perfect sway are, perhaps, 75%. So if you have 4 women who all have near perfect sways, 3 should end up with girls (or boys). Even with a near perfect sway, the odds of an opposite are 1 in 4. And lots of people don't think perfect sways are even 75% effective.
Here's another way to look at it. I just had a miscarriage at 13 weeks. Two weeks earlier I saw the baby's heartbeat on an ultrasound and saw it move. My odds of having a take home baby at that point were 90-95+%. Those odds were significantly higher than my odds of a having a girl, even if my sway had been a lot better than it was. And yet, my baby still died. Loads of other women also lose their babies in the second and third trimester even when the odds are drastically in their favor. Does this mean doctors are wrong and seeing a heartbeat or reaching various pregnancy milestones have no impact on the chances of a healthy pregnancy? Nope. It just means that sometimes people end up on the unlucky side of the statistics, and it sucks. :(
I suspect the effectiveness of the "average" incomplete sway that most people do is 60-70%. 60% is definitely better than 50%, and if most sways are 60% effective, that means women have increased their odds of getting the gender they desire. Now, instead of having 5 women in 10 having girls (or boys), 6 in 10 will. But people need to keep in mind that neither 60% nor 70% nor even 80% is the same thing as 100%. It is inevitable that there will be opposites with swaying, and it is impossible to judge swaying by looking at a single person's experience. While I do think swaying increases a person's odds, I don't think swaying is even remotely close to a guarantee of one's desired gender.