After giving birth to three boys, Laura Diamond wanted balance. She wasn’t going to take chances.

“I really, really wanted a girl,” she said. “I was going to do whatever I could to make it happen.”

The personal trainer and her husband, David, a film studio vice president, went through an in vitro procedure to pick the sex of pre-embryos before they were implanted. Gender selection is banned in Canada, Great Britain and several other countries except for situations in which the tests limit exposure to certain diseases or serve other medical needs.

The procedure, although it raises concern for ethicists, is legal in the United States.

The process, pre-implantation genetic diagnosis, can cost as much as $14,000, although Diamond’s costs were about one-third of that because she went through in vitro with her eldest boys, who are twins. She used frozen embryos, and the result was a baby girl.

Now 3, Cecilia wears her hair straight and long. She wheels around on a pink tricycle.

“Everyone calls her Mini-Me,” said Laura Diamond, trying to explain how genetic testing meant closure for her family. “I can move on. You don’t feel complete unless you have one of each. It brings a balance.”

Ethicists, however, worry that choosing a baby’s sex can bring gender inequity, citing China, where laws limiting families to one child mean parents sometimes abort pregnancies in which the fetus is female.

Critics worry, too, about using genetics for purposes beyond minimizing the risk of illness.

“I think it’s a bad idea,” said ethicist Miriam Piven Cotler, visiting professor at the Bioethics Institute at Loyola Marymount University in Los Angeles. “It’s part of a larger question: What are the limits beyond which we shouldn’t go to dictate what kind of children we want? It’s this general notion that children are commodities and we can mail-order them.”

Different methods are available, with the DNA analysis of chromosomes generally considered the most accurate. Three days after eggs are fertilized in a laboratory, one cell is removed and can be evaluated for genetic vulnerability to Down syndrome, hemophilia, kidney disease and cystic fibrosis.

The testing also identifies whether the pre-embryos have XY chromosomes, indicating a boy, or XX chromosomes for a girl. The desired embryos are implanted, and the rest are stored or discarded.

“People have been trying to control the sex of their offspring since the dawn of man,” said David Hill, scientific director of the ART Reproductive Center lab in Beverly Hills. “Wearing socks at certain parts of the day there are all sorts of things that have been thrown up against the wall.”

The ART Reproductive Center is affiliated with the Southern California Reproductive Center.

Many embryos analyzed by the center come from couples who are just starting families and can’t have children naturally.

In the United States, the American Congress of Obstetricians and Gynecologists and the American Society for Reproductive Medicine are concerned about gender selection.

The latter group says the least justifiable scenario involves couples who go through in vitro only to choose the sex of a child.

Ethicists say prohibitions and concerns are driven by fears of creating or reinforcing gender biases.

“I think that’s not only immoral; it also makes for lousy demographics,” Cotler said. “In some cultures, boys are highly preferred over girls. We’re sort of messing with Mother Nature here. There are some limits beyond which we have to say it’s not wise to go.”

Other skeptics say the issue revolves around the discarded embryos or cite the role of DNA screening in medicine.

“In medicine, you don’t treat preferences. You treat disease,” said Art Caplan, director of the Center for Bioethics at the University of Pennsylvania. “Gender is not a disease. What we’re really talking about is pure preference. At the end of the day, sex is a lousy reason to get a medical procedure.”