Ummmmmmm I'm not sure.
I do know that rh blood types can only have one sex baby.
Like my sister is rh- i think it is. . . sorry my brain is lost right now but she has had 3 girls and misscarried on her baby boy.
The same with her dad he has only had a girl (my sister)
Her granmother and uncles also have all had either boys and lost their girls or girls and lost their boys.

The sex of the baby is determined from the father... because the chromosones of a female is xx and the chromosomes of a male is xy so they get split up when eggs and sperm are made. so no matter what the females egg is going to be an x. However the male has an even amount of x sperms and y sperms so it just depends on which one makes it to the egg first. I also heard that the smartest sperm of the bunch is the one that reaches the egg.

This happened with my fiance's family they have all boys, as far back as you go they are all boys!!! but they also all only seem to have had two children. My fiance's dad had his third child last year and it was a girl!!!!!! Everyone was amazed!

This is my third child, but its only my fiance's second but we are hoping we can follow the trend and bring on some girls!! lol!

LittleCaseysMommyJen - My sister is rh negative, she had a miscarriage with her first baby then went on to have 2 boys safely does this mean that her first child was more likely to have been a girl then?? I didnt know they were only likely to have one sex, I thought it was more down to the babies blood type

How i look at it I would believe it was a girl. I am not a scientist and I don't think it's been fully proved yet, but my sister disscussed it with her Obgyn and her doc. told her that studies were being done.

same thing with my husband...his whole family is males.. they have 2 female cousins and about 30 boys and we are having.................... a girl.
everyone was shocked and thought for sure it would be a boy but.. weve had 5 4d ultrasounds and are pretty positive its a girl.
i think it can really go either way.

There are more boys in both mine and .Dom's family but we're having a little girl, all my cousins are boys my dad only has brothers and .Dom has a brother and only one girl cousin and only one aunt

I'm not sure but I know it can be true that first borns have a certain gender, like in my family, all of my nan's 8 children, that have had children, apart from her first daughter had a girl first. My mum had me, my nan had her first girl so I was expecting Paige to be a girl really. Unless its just the blokes we go for. lol. I wouldn't worry too much. You never know what might happen.

i dont think thats quite true, my sister is rh- she had a daughter, aborted one due to circumstances then got pregnant again and had a baby boy. so the rh- i dont think that one holds up

my family is weird, my grandpa had 6 brothers, no girls my grandma had 3 boys and 1 girl, my mom had 2 girls 1 boy in that order. my uncle has aboy and a girl in that order, my sister has a girl and boy in that order then i have a boy and a girl in that order. SO hmm i dunno how genetics would work, but so far my familys pretty evened out with the boy girl thing maybe we just got lucky, i think it all has to do with sex positions and such

My friend has a rh blood type and has a boy (2) and a little girl (4months)

I am rh- and I have never heard of that.

i did some google searching and found several places that talks about techniques to increase the chances for having a girl or a boy. Seems interesting. They talk about the ph and how X sperm survive better at higher ph than y sperms and so on. I think I'm going to do more research on that one.

i'm rh- and i have a healthy 3 month old son.. & .in my family, it's girls, girls, girls.. hardly any boys. but i had a boy. it's really just the luck of the draw..

RH Factor doesn't work like that.

If the mother is RH- and the dad is RH , it can make a baby with RH blood. In the off chance that the baby's blood crossing into the mother's bloodstream, the mother's body will create antibodies to fight the RH in the baby's blood. This causes anemia and other hemolytic (blood destroying) issues. So, before the mother's body is "sensitized" (when it gets a taste of the 'badguy'), they give her shots to inhibit the production of those antibodies.

Basically, it's got nothing to do with gender.

uh, i studied a little bit about genetics in my university classes and i don't remember them ever mentioning sex positions being a factor lol. i think these things are random for a reason. we can't start manufacturing our babies to suit ourselves. if you have heard something about increasing your p.H that's one thing, but you're talking about millions of microscopic sperm cells that each have a unique genetic code. nature designed it that way because it's the way that works best. why not just be amazed at the randomness of it all and be just as happy whether it's a boy or a girl?

i agree!

I have rh- and i have 2 boys and a girl.

My husbands family favour boys. They do determine the gender, and i was so surprised that we got a girl. We had 2 boys, his brother had 1 boy, his father had 3 boys and his father's father has 11 boys 2 girls. I think #7 or 8 was the first girl

I remember reading somewhere that (x) female sperm were stronger than (y) male sperm. But the males were smaller and quicker. So the position thing would work if the sperm was ejaculated near the opening of the cervix the female sperm would be better of because they were the stronger ones and were more able to make the longer journey. Where as, if sperm was ejaculated at the top of the cervix the boys would fare better because they were quicker!! It works for ph too. one sort (I cant remember which!) Can kill of sperm meaning that the stronger females will have a better chance, the other ph helps the sperm so boys would do better. It works for lots of situations, such as timing intercourse around ovulation.
I looked up on it quite abit and the was quite alot of evidence to back it. Although for me it ttc was hard enough as it was without having to think about this lot too!! I have 2 boys and am quite likely pregnant with the third!! But who cares what the sex is, just be happy with what you have got!