Here's a nicely written summary of the research, along with evolution of beliefs in the medical community. The original (pre-80's) prevailing assumption was that it was urine, no further discussion needed. That has changed quite a bit with more data.
This reminds me of the same issues regarding prostate cancer -- the assumption that high testosterone both caused and fueled tumors was regarded as so self-evident that it was never challenged... until about ten years ago when it was turned on its head and hypogonadism was shown to be a greater oncogenic risk.
Female ejaculation
The relevant sections:
Is female ejaculation caused by urine leakage?
Until the 1980s, most doctors who were aware of the phenomenon of ejaculation used to assume the fluid must be urine. As a treatment, they would tend to recommend exercises to build up the pelvic muscles.
And many women do leak a little urine during sex and during other activities as well. This is called 'stress incontinence' and it happens to vast numbers of females when they sneeze, cough or laugh. It is particularly common in those who have had children.
However, when urine leaks during sex, it's often during foreplay or vigorous intercourse rather than at orgasm.
In 1982 the publication of a highly influential book by US sex experts Whipple, Perry and Ladas changed these views. They suggested the fluid wasn't urine, but was instead a 'juice' secreted by glands that were said to be the equivalent of the male prostate.
What research has been done on the fluid?
There hasn't been enough research on the fluid (ejaculate) ? partly because it's difficult to obtain adequate supplies of it for investigation. Also, large scientific funds tend to be available for life-threatening diseases rather than for sexual problems.
However, recent research suggests the ejaculate is an alkaline liquid that isn't like urine, because it doesn't contain urea or creatinine, which are normal urinary constituents.
The fluid tends to be clear coloured and doesn't stain bedclothes yellow ? again, unlike urine.
Researchers have claimed that it contains some chemical ingredients similar to those produced by the male prostate ? notably PSA (prostate-specific antigen). It is also said to contain two sugars: glucose and fructose.
Since 2000, an increasing number of researchers have suggested the liquid may be the secretion of Skene's glands (the paraurethral glands). These are tiny structures which lie around the female urethra (the urinary pipe).
In 2007, the well-known Viennese researcher Dr Florian Wimpissinger published an important study on two women who habitually ejaculated. He and his colleagues found that the ejaculate from these two females was chemically very different from that of their urine.
In particular, it contained more prostatic acid phosphatase (PAP), more prostate-specific antigen (PSA), and also some glucose.
She certainly got her foreplay every night so make your woman happy and do her right or she won't recipocate.
