After years of infertility treatments and three heartbreaking miscarriages, Molly Magnani stared at the black and white monitor as an ultrasound wand moved over her belly. She saw one fetus, then another. Then — wait — were there more?

You have four, her doctor said. Her 8-year-old son cheered. Her husband, David, turned white and was told to sit down.

"And I just was laying there thinking, 'What have I gotten myself into?"' Magnani recalled. "You're overjoyed and excited, but I remember being scared to death."

For infertile couples who have longed to fill their homes with children, the sudden prospect of twins, triplets or more can be thrilling at first. But the risks of a multiple pregnancy means they may quickly face the agonizing decision of whether to abort some fetuses to give the others a better chance to live.

It's an issue highlighted this month by the births of sets of sextuplets in Minnesota and Arizona. Four of the six babies born June 10 to a Minnesota mother have died, and the others are in critical condition. In Arizona, the mother was treated for acute heart failure after giving birth.

"I think that these instances give the whole question of fertility treatment a black eye because the results are so tragic, and the costs are so enormous," said Dr. Theodore Nagel, a reproductive endocrinologist at the University of Minnesota.

Having a high number of fetuses can be prevented if the treatments are done carefully, he said.

The random removal of fetuses is called multifetal reduction. More frequent is selective reduction, in which couples pinpoint fetuses to be removed — perhaps those with abnormalities.

The parents of the Minnesota sextuplets, Ryan and Brianna Morrison, used fertility drugs. Doctors encouraged them to consider removing some of the fetuses, but it was "not an option for us," the couple wrote on their Web site.

"We understand that the risk is high, but we also understand that these little ones are much more than six fetuses. Each one of them is a miracle given to us by God," they wrote before the births.

The Morrisons have declined to be interviewed.

Prematurity is the prime complication in multiple births, where underdeveloped babies are more likely to face serious problems like cerebral palsy, mental retardation and chronic lung disease. While just 7 percent of twins are born early, 92 percent of triplets are born prematurely, said Dr. Diane Ashton, deputy medical director of the March of Dimes. Quadruplets or higher-count births are always premature, she said.

The Morrison sextuplets were born about 4 1/2 months early, and they ranged in size from just 11 ounces to a little more than a pound.

That gestation period is right on the edge of viability. Babies born at 21 weeks usually do not live, Ashton said; at 23 weeks, viability jumps to about 70 percent.

Nagel, who is not involved in the Morrison case, said it's important to control infertility treatments. Skilled doctors manage the process to avoid the possibility of multiples. But sometimes, he said, fertility drugs are administered inappropriately by obstetricians, gynecologists and internists without special training.

Even when the drugs are properly managed, multiple-fetus pregnancies do happen.

Los Angeles Times columnist and automotive critic Dan Neil and his wife, Tina Larsen, used in vitro fertilization to conceive. On their third attempt, they ended up with five embryos — none of which seemed particularly strong.

Their doctor said the embryos would be implanted only if the couple agreed to a reduction if too many developed. They agreed — and ended up with four fetuses.

"We are pro-choice people," said Neil. "Yet no sensible person takes this decision lightly. ... They were potential babies, and we had been trying so hard to have babies."

Neil, who wrote a piece in May about his decision, said considering the risks, eliminating two fetuses was a smart choice.

"(Reduction) wasn't something that we would want ... but when you start to emotionally and politically marginalize obstetrical procedures, you create vast unintended consequences for fertility medicine," Neil said.

Larsen is in her 23rd week and the couple is looking forward to two baby girls — already named Rosalind and Vivian — due in October.

Magnani was undergoing intrauterine insemination and her doctors told her during one cycle that she had a potential for six fetuses. She was asked if she wanted to proceed.

After so many miscarriages and years of trying, she thought the more eggs the better. When she found out she was having four, she and her husband decided they would choose selective reduction only if there was a genetic problem that would affect the other fetuses. Plus, she worried the procedure could force a miscarriage.

"We had tried too hard, and come too far," Magnani said. "And I thought, you know, I couldn't do that. I couldn't deal with losing all of them."

In the 25th week, one of the fetuses began moving down the birth canal — a process that took about a week. Martin lived only 2 1/2 hours, but Magnani believes he saved his brother and sisters, who were born a day later. Now, they're happy, healthy 5-year-olds.

"Everything's normal," she said. "Whatever they encounter now, they probably would've anyway. So a little of the guilt starts to dissipate. You feel that you did your best for them."