(CNN) -- Genetic screening techniques that allow parents to choose their children's gender are now more accurate than ever and are becoming increasingly mainstream, but experts are divided over whether the technology should be used in this way.
A technique called pre-implantation genetic diagnosis (PGD) was originally developed two decades ago to allow embryos to be tested for genetic disease. It requires parents to use in vitro fertilization, where eggs are fertilized outside the womb.
With PGD, the embryos are tested for genetic disorders and only those that are free of disease are transferred to the mother's uterus. It means that parents who carry genetic defects can ensure they don't pass on a genetic illness to their children.
But PGD also can also be used to allow people undergoing in-vitro fertilization to select the gender of the embryo implanted in the mother's uterus.
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Using PGD for gender selection is banned in most countries, but it is legal in the U.S., where the procedure costs around $18,000, including in-vitro fertilization.
Los Angeles fertility expert Dr. Jeffrey Steinberg uses PGD for gender selection. He told CNN's Vital Signs program that many of his American clients already have children of one gender and are trying to achieve "family balancing."
He added that 70 percent of his patients are from countries where the procedure is banned.
Critics question the ethics of gender selection, and some argue that it could lead to a gender imbalance, particularly in societies with a traditional preference for boys.
"If anything, there's a slight preponderance for females, and this is contrary to everything that is publicized, and clearly it varies by country," said Steinberg.
"China is strongly in favor of boys, as we would suspect. India, strongly in favor of boys. But when you look at the world in general, it's 50-50"
Dr. Mark Hughes, who pioneered PGD, he has concerns about its use for non-medical purposes. He told CNN, "It definitely is an expanded reproductive choice. The question is, is it medicine? Is it something that doctors should be involved in?"
But Steinberg argues that it's wrong to limit scientific capabilities. "I say to critics that the last thing in the world that you want to do is put the handcuffs on science.
"We've been giving women expanded reproductive choices for 50 years. This is another choice."
Although the technology for gender selection is becoming more widespread, it remains controversial. Some feel that it's "playing God," while others welcome having more choice in family planning.
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