Drajeesh

The main factor that determines the gender of a baby are the chromosomes.
(Chromosome=A circular strand of DNA in bacteria (and also a protein) that contains the hereditary information necessary for cell life).
 
In a wider concept, there are two kinds of chromosomes: an X chromosome and a Y chromosome.
 
The unfertilised egg already contains an X chromosome, which leaves two options at the time of conception:
 


An X chromosome can be added to the already present X chromosome, in which case the baby will be a girl.
A Y chromosome can be added to the already present X chromosome, in which case the baby will be a boy.

There is also a risk factor: sometimes, on top of the X or Y chromosome, an extra chromosome gets added at the time of conception, in which case the baby is usually born with Down's Syndrome. 
There are some methods, which claim to help determine the baby's gender, such as calculating the ovulation time, and then having sex at a certain number of days from ovulation time, but that is very theoretical, and difficult to plan properly.
 
Furthermore, there are also lots of old wives tales about when and/or how to have sex in order to make sure your baby is the gender you want it to be.
 
But, coming back to the original question: I understand from your question that you would like to know the gender of your baby, based upon your and your husband's blood groups, well, blood groups do not determine the gender of a baby, but they do influence the blood type your baby will be born with.
 
The best thing to do if you want to know what gender your baby will be is to have an ultrasound (or, a scan, as it is more commonly known).
Doctors have been known to get the gender wrong using this type of test, although the chances for that are very minimal, mistakes can happen, of course, when the baby is laying in an awkward position.
 
There is also a home testing gender kit available, which is similar to a home pregnancy test, but this type of test is highly questioned on its reliability by a majority of scientists.
 
So, do not rely on tales you hear or things people write about blood types determining the gender of your baby, just do it the proper way, make an appointment with a gynaecologist and have an ultrasound done, this is still your best bet.
 
Also, if gender were determined by the blood groups of the father and mother, that would mean all your children would be of the same sex, which is clearly not the case in many families.
 
Finally, all the best of luck with the pregnancy, and best wishes for a smooth birth of a happy and healthy baby.