The number of male babies born to couples who perform fertility treatments or which is known as sperm injection or ICSI (intracytoplasmic sperm injection) is less than the woman carrying naturally.

In a national study in the United States there are an average of 105 baby boys every 100 girls. However, recent research has found this ratio is reversed when the baby is conceived through sperm injection or ICSI program.

More than 15,000 babies born in America in 2005 found that male babies born with ICSI program fewer than average number of children born male who was born naturally.

The effect was seen when ICSI is done by using blastocyst embryos, - that is, embryos that matured a few days longer before it moved to the mother's womb. This allows doctors to transfer fewer embryos to reduce the chances of having twins three or more.

Among couples who undergo this procedure, there are only birthrate boys under 50 percent, compared with the normal average of 52.5 percent in 2005, according to findings published in the journal Fertility & Sterility.

ICSI is done by injecting a single sperm from the father directly into an egg taken from the mother. If one or more embryos developed for several days, it will be transferred to the womb.

ICSI treatment done for reasons of fertility problems such men low sperm count or low quality. However, ICSI was also performed because of infertility problems is not clear who ultimately many clinics in the U.S. generalize ICSI treatment for infertility patients.

As quoted by Reuters research led by Dr. Barbara Luke from Michigan State University in East Lansing United States, have not been able to find the connection clear why ICSI reduce the number of births boys.

But the researchers concluded ICSI may reduce the sex ratio and did ICSI is recommended only if absolutely necessary to prevent side effects.