Not to sound too stupid i hope but, when exactly is the sex of your baby?

The sex of your baby is determined at conception, but the extenal genitals don't appear until week 9 and by week twelve they are completely developed into either male or female genitals. But we can't see anything until about week 20 during an ultra-sound!!! Hope that answers your question...

It is determined at conception, as in if a sperm with the X chromosome reaches the egg first it's a girl, and if it's a Y chromosome it's a boy. But it won't show at all physically for a while, at least until the third month, all fetuses will look the same with a small lump between the legs. In a girl, this shrinks in and becomes the clit. In a boy, it grows and becomes the penis. The internal sex organs become either ovaries or testicles at this time. But the biological makeup to determine which will happen was chosen the instant a sperm touched an egg.

At conception.

It depends on which chromosome the fertilizing sperm is. Women always carry the X chromosome. So X could be considered female, and Y is male.

XX=girl, and XY= boy

I just looked up a site, and here is a more detailed explanation:

Background

The sex of a child is determined by the specific sperm cell fertilizing the egg at the time of conception (view sperm cells). Sperm cells carrying an X chromosome result in a female and those carrying a Y chromosome result in a male. Semen contains approximately 50% female and 50% male sperm cells. Any system designed to separate X- (female) and Y- (male) sperm cells must have (1) the ability to identify and measure a difference between female and male sperm cells, (2) separate the cells based on the measurable difference, and (3) directly determine the results of the separation process.

Scientific Basis

The MicroSort technology is based on the fact that the X chromosome is substantially larger than the Y chromosome (view X&Y chromosome). Since chromosomes are made of DNA, human sperm cells having an X chromosome will contain approximately 2.8% more total DNA than sperm cells having a Y chromosome . This DNA difference can be measured and the X- and Y-bearing sperm cells individually separated using a modified flow cytometer instrument (view representative instrument). The resulting purity (enrichment) of the separated sperm cells can be determined by a DNA analysis method called FISH (fluorescence in situ hybridization) in a small unused portion of the sorted sample. FISH uses DNA probes that specifically attach to either the X or Y chromosome in sperm and emit a red/pink color for X-bearing sperm and green for Y-bearing sperm. The X- and Y-bearing sperm can be identified and counted under a microscope to determine the purity (view FISH analysis).

Conception, x and y chromosomes.

All of what we are made of is stored in our genetic material called chromosomes. Humans have 23 pairs of chromosomes (46 in all) which are arranged in eight groups based on size and shape (It takes a geneticist to tell the difference). The last group are called the sex chromosomes. Females (46,XX), are composed of 2 (X) sex chromosomes. Males (46,XY) have an (X) and a (Y) sex chromosome.

In formation of the egg and sperm, only one-half (23) of the total number (46) of chromosomes is present in each. The mother can only contribute an X chromosome The egg has 23 chromosomes with an X chromosome). Whereas the father can contribute either an X or a Y chromosome (The sperm has 23 chromosomes with either an X or a Y chromosome). If the sperm cell that combines with the egg contains an X chromosome the result will be a GIRL (XX). If the sperm cell contains a Y chromosome the result will be a BOY (XY).

From the moment of conception the babys sex is determined. Anything you do after that to insure one sex over the other is pointless!!

It is determined the moment of conception, a woman has the X chromosome and the male can add another X to create a girl or add a Y to create a boy.

Conception. The man's sperm determines what the sex of the baby will be.

the sex of the baby is determined by the sperm at the moment of conception. the male chrosome of XY can contribute an X (for girl) or a Y (for boy) . The feamle is XX.

At the moment of conception. It depends on whether the sperm carries an X (girl) or Y (boy) chromosome.

Still, some babies that are genetically male develop physically as girls because, for some reason, the male hormones that would cause them to develop male anatomy aren't released.

Conception-the sperm determines the sex of the baby.