It was the last piece of advice Thomas and Amanda Stansel wanted to hear. But their fertility doctor was delivering it, without sugarcoating.

Reduce, or you will lose them all, he told them.

For more than a year the Stansels had been relying on Dr. George Grunert, one of the busiest fertility doctors in Houston, to produce his industry’s coveted product — a healthy baby. He was using a common procedure called intrauterine insemination, which involved injecting sperm into Mrs. Stansel’s uterus after hormone shots.

But something had gone wrong. In April, an ultrasound revealed that Mrs. Stansel was carrying not one but six babies, and Dr. Grunert was recommending a procedure known as selective reduction, in which some of the fetuses would be eliminated.

The Stansels rejected Dr. Grunert’s advice and, since then, their vision of a family has collapsed into excruciating loss: the deaths of three children after their premature births on Aug. 4. More than two months later, the three other infants remain in neonatal intensive care, their futures uncertain. One of them, Ashlyn, is near death.

“I feel like we bonded with all of them, the short time they were here,” Mr. Stansel said. “We were able to hold them before they passed away.”

The birth of octuplets in California in January placed the onus for large multiple births on in vitro fertilization, a treatment in which eggs are joined with sperm in a petri dish and returned to the womb for gestation.

But the procedure the Stansels used is actually the major cause of quadruplets, quintuplets and sextuplets — the most dangerous pregnancies for both mother and children. While less effective than IVF, intrauterine insemination is used at least twice as frequently because it is less invasive, cheaper and more likely to be covered by insurance, interviews and data show.

Multiples can occur when the high-potency hormones frequently used with the procedure overstimulate the ovaries and produce large numbers of eggs. Parents are then left with the kind of tough choices the Stansels faced: whether to eliminate some of the fetuses or keep the babies and face extraordinary risks.

“I think, and so many of my colleagues think, it’s a primitive approach,” said Dr. Sherman Silber, a fertility doctor in St. Louis. “The pregnancy rate is lower than IVF, and you don’t have control over multiples.”

In treating women who are having trouble getting pregnant, most doctors try low-potency fertility pills first, then intrauterine insemination with the hormone injections and in vitro fertilization as a last resort. Some insurance plans require women undergoing fertility treatments to have several rounds of intrauterine insemination before they will pay for in vitro fertilization. Because of the cost, other plans cover intrauterine insemination but not in vitro.

But a recent study led by Dartmouth Medical School suggested that because IUI often requires repeated tries, it would ultimately lower both costs and the risk of large multiple births if many patients avoided the procedure and moved straight to IVF.

Unlike IVF, intrauterine insemination is not tracked by any government agency, so there are no official statistics on how many pregnancies result from it. But other studies and the Centers for Disease Control and Prevention have found that IUI and other similar treatments cause more large multiple births than in vitro fertilization, contributing to the nation’s 12.7 percent rate of preterm babies.

Experts agree that at least 20 percent of the pregnancies are multiples. Most are twins, but one 1999 study found that 8 percent of the pregnancies with injectable hormones and insemination were triplets and quadruplets. The more babies, the greater the risk. Quadruplets, for example, have a more than 10 percent chance of dying in infancy.

Pregnancies with quadruplets or more are unusual, and shocking when they occur.

Jon and Kate Gosselin, who already had twins, had wanted just one more baby, but IUI resulted in the sextuplets made famous on the TLC program “Jon & Kate Plus 8.” The same thing happened to Jenny and Bryan Masche, stars of “Raising Sextuplets,” the TV program on WE, the Women’s Entertainment network.

Mrs. Masche became seriously ill from acute heart failure brought on by her pregnancy, but she has recovered. The Gosselins have separated under the stress of raising multiples. But the Masche and the Gosselin sextuplets are the success stories. They are healthy.

Women who have gone through large multiple pregnancies with poorer results say the shows give viewers a misleading picture by failing to present the wreckage left behind in many cases — babies who are stillborn, spend months in the hospital undergoing painful procedures that require morphine or suffer from long-term disabilities.

Multiple babies who arrive very early require the highest level of acute care for a longer time than any other patients. Despite the lower cost of IUI on the front end, many doctors point out that insurance plans bear higher costs when IUI goes awry and large broods are born.

“We have families that have babies here for three or four or five months, and they’re having discussions with their insurance companies because they have reached the lifetime limit of their medical coverage,” said Dr. Scott Jarriel, a neonatologist who works at the Woman’s Hospital of Texas and treats the Stansel babies.

An Unwelcome Surprise

The Stansels’ decision to use intrauterine insemination was based largely on finances. The treatment can cost as little as $2,000 to $3,000, compared with $12,000 to $25,000 for in vitro fertilization.

Mrs. Stansel’s insurance would not cover IVF but would pay for six rounds of IUI. She consulted Dr. Grunert in April 2008, just over a year after the Stansels were married.

Mrs. Stansel, 33, first tried clomiphene, a fertility pill, but that did not work. Then she moved to the next step, a popular injectable drug, Gonal-F. The drug stimulated her ovaries in preparation for intrauterine insemination.

She became pregnant with twins after her first round of IUI. But she miscarried on Sept. 24, 2008, at 18 weeks.

Within months, Mrs. Stansel underwent another round of intrauterine insemination, but in January she learned that it was an ectopic pregnancy, one that develops outside the uterus.

The Stansels decided to try again.

Before conducting their third insemination procedure in March, Dr. Grunert was monitoring Mrs. Stansel’s ovaries with ultrasound. He saw only two developing eggs mature enough to potentially be fertilized.

Instead, six fetuses developed.

“It was obviously a shock,” Dr. Grunert said, “hopefully a once-in-a-lifetime experience.” Dr. Grunert has been in practice for 30 years and said it had never happened to him before.

Dr. Richard P. Dickey, a specialist in the New Orleans area who has conducted research on hormone use in reproductive medicine, said that IUI is normally a safe procedure. But, he said, some doctors prescribed excessive doses of the hormone injections, which could overstimulate the ovaries.

Or they use the injections before trying a cheaper oral drug that produces fewer multiples, Dr Dickey said. The drug is less successful than the injections.

A round of oral drugs is available for $20 and does not require extensive monitoring. A round of injectable drugs costs $1,000 or more. Clinics can make additional money when the injectables are used because they require the use of repeated ultrasounds and other testing, which can add up to $1,000 to $2,000.

“There’s a money factor, unfortunately, in this,” Dr. Dickey said. “There is a factor of not paying enough attention, and doctors aren’t sufficiently aware of the dangers of multiple pregnancy.”

Deciding to Eliminate

Three years ago, Keira Sorrells, an interior decorator in Monroe, Ga., had found herself in a predicament similar to the Stansels’. After intrauterine insemination, Mrs. Sorrells learned that she was carrying quintuplets.

She said she was in shock at hearing the news and ill prepared for the next step. Before he had even closed the door to his office, her fertility doctor suggested selective reduction to Mrs. Sorrells and her husband, Richard. “We had never heard of it,” Mrs. Sorrells said.

“I think there’s a huge problem in the reproductive technology industry,” Mrs. Sorrells said. “I was told the chances that I would have triplets were less than 1 percent. There was no talk of being faced with a decision like that until the day that we had the ultrasound. Then you have two weeks to decide. And you don’t get counseling from anybody.”

In the next two weeks, Mrs. Sorrells and her husband struggled to make a decision on whether to eliminate fetuses and, if so, how many. The specialist gave her 50-50 odds that her babies would survive and said twins or a single baby would be safer.

The process of “selective reduction” involves injecting potassium chloride to the heart region of the fetuses, which then generally disappear on their own, absorbed into surrounding tissue.

Hoping to save as many babies as possible, Mrs. Sorrells decided instead to eliminate two of the fetuses, reducing her pregnancy to triplets. Even then, her pregnancy was troubled. She developed pre-eclampsia, a complication of pregnancy that includes rapidly increasing blood pressure.

On Dec. 20, 2006, at 25 weeks and 5 days gestation, Mrs. Sorrells had to have an emergency Caesarean section.

The most severely ill of her three premature daughters, Zoe Rose, was born with multiple problems. Zoe died last year of a drug-resistant staphylococcus infection at age 14 months — nine of them spent in a neonatal intensive care unit. The Sorrellses’ two surviving daughters, Lily and Avery, are doing well despite their extreme prematurity and four-month stays in neonatal intensive care.

The Sorrellses have formed the Zoe Rose Memorial Foundation with the goal of helping parents who have premature children.

Dr. Brian Kirshon, a doctor in Houston who specializes in high-risk pregnancies, says some couples do not understand the implications of multiple births, even when the risks are explained.

“I think a lot of them don’t really understand the risks of prematurity, the risks of losing their babies, the risk of long-term complications, blindness, deafness, cerebral palsy, development delay when they have extremely premature babies, or the ultimate risk of losing their marriage,” Dr. Kirshon said.

Taking Another Path

When Dr. Grunert discovered that Mrs. Stansel was carrying multiple fetuses, he handicapped her odds of delivering six healthy infants at practically zero.

Eliminating some of the fetuses would give the others the best chance for survival.

Dr. Mark I. Evans, a doctor in Manhattan who is among a small group nationwide that specializes in selective reductions, estimates that 1,000 to 2,000 reductions are performed annually in this country, usually in the first trimester. Doctors generally discuss reduction as a possibility in pregnancies with triplets or more.

Many opponents criticize selective reduction as a form of abortion. And for many parents who elect to carry all of the fetuses, the decision often hinges on religious convictions. There is also a chance, up to 5 percent, that selective reduction will be followed by a miscarriage of all the fetuses, according to the American Society for Reproductive Medicine.

For the Stansels, the decision was influenced by their membership in the Church of Jesus Christ of Latter-day Saints. The church generally opposes abortion. After learning that Mrs. Stansel was carrying sextuplets, the Stansels decided to meet with church elders and consult with a reduction specialist.

“It just never felt right,” Mr. Stansel said. “We prayed many nights. A lot of sleepless nights. Originally we thought we might do the reduction. We chose to carry all six and, we believe, let God do what he’s going to do.”

On July 3, in her 19th week of pregnancy, Mrs. Stansel was admitted to the Woman’s Hospital of Texas for monitoring, under the care of Dr. Kirshon, an expert at delivering multiples. By early August, she began having contractions that did not stop with medication and threatened to rupture her cervix.

“There wasn’t anything we could do,” Dr. Kirshon said. Instead, Mrs. Stansel delivered the sextuplets on Aug. 4, about 14 weeks premature. The babies were born so early that no medical care would have been rendered unless the parents requested it.

Dr. Jarriel, the neonatologist, said the survival rate of babies at the stage they were born was about 60 percent to 65 percent. If they survived, the Stansels were told, there was a 100 percent chance that they would have problems.

But the couple asked the hospital for the most extraordinary measures to save them.

“We wanted to do all we could for them, to save them,” Mr. Stansel said.

“Give them that chance,” Mrs. Stansel added. “That’s the doctors giving their statistics. God doesn’t work in statistics.”

The babies — Ashlyn, Braden, Dallin, Haley, Kaitlyn and Rachel — ranged in weight from 12.3 ounces to 1 pound, 1 ounce. They were each less than a foot long.

Dallin was the first to die. Blood seeped into his lungs from an open heart valve, the Stansels said. Kaitlyn soon followed. Braden lived for two weeks before an infection entered his trachea and killed him.

“He fought hard,” said Mr. Stansel, 32. “His lungs just got so inflated, they crowded out his heart.”

The three were buried on Aug. 22 in Austin, Mrs. Stansel’s hometown, in a single casket. “They came into the world together, and they’ll leave together,” Mr. Stansel said.

The three remaining Stansel babies have been in precarious health in the neonatal intensive care unit.

The couple has been making daily visits to the hospital and are now able to hold the girls for a short time. All three of the infants are still attached to ventilators and feeding tubes, which deliver their mother’s milk.

Rachel, who now weighs 3 pounds, 7 ounces, is doing better than the other two girls and is slowly being weaned off intravenous nutrition. On Thursday, Haley, who now weighs about three pounds, underwent surgery to remove a bowel obstruction.

Ashlyn, the most severely ill, was experiencing kidney failure Sunday. Her father said in an e-mail message that he did not think she was going to make it.

“Our heart breaks for her,” her parents wrote in a posting on a blog they are keeping.

The blog has drawn thousands of comments from supporters. But some critics have also written, saying the Stansels should not have continued the pregnancy knowing the poor odds. Some cited the pain and suffering of extremely preterm babies.

“I knew the babies would come early,” Mr. Stansel said in a recent interview at the couple’s suburban Houston home, near Humble. “I knew they’d be in the NICU. I knew there would be challenges.”

Mrs. Stansel added: “I don’t think I realized how tough it would be.”

Scary. Like aliens. That is how Kerry Mastera remembers her twins, Max and Wes, in the traumatic days after they were born nine weeks early. Machines forced air into the infants’ lungs, pushing their tiny chests up and down in artificial heaves. Tubes delivered nourishment. They were so small her husband’s wedding band fit around an entire baby foot.

Having a family had been an elusive goal for Jeff and Kerry Mastera, a blur of more than two years, dozens of doctor visits and four tries with a procedure called intrauterine insemination, all failures. In one year, the Masteras spent 23 percent of their income on fertility treatments.

The couple had nearly given up, but last year they decided to try once more, this time through in-vitro fertilization. Pregnancy quickly followed, as did the Mastera boys, who arrived at the Swedish Medical Center in Denver on Feb. 16 at 3 pounds, 1 ounce apiece. Kept alive in a neonatal intensive care unit, Max remained in the hospital 43 days; Wes came home in 51.

By the time it was over, medical bills for the boys exceeded $1.2 million.

Eight months later, the extraordinary effort seems worth it to the Masteras, who live in Aurora, Colo. The babies are thriving and developing their own personalities — Wes, the noisy and demanding; Max, the quiet and serious. Like many other twins conceived through in-vitro fertilization, the Mastera boys will go down in the record books as a success — both for the fertility clinic that helped create them and the neonatologists who nursed them to health.

But an exploration of the fertility industry reveals that the success comes with a price. While IVF creates thousands of new families a year, an increasing number of the newborns are twins, and they carry special risks often overlooked in the desire to produce babies.

While most twins go home without serious complications, government statistics show that 60 percent of them are born prematurely. That increases their chances of death in the first few days of life, as well as other problems including mental retardation, eye and ear impairments and learning disabilities. And women carrying twins are at greater risk of pregnancy complications.

In fact, leaders of the fertility industry and government health officials say that twins are a risk that should be avoided in fertility treatments. But they also acknowledge that they have had difficulty curtailing the trend.

Many fertility doctors routinely ignore their industry’s own guidelines, which encourage the use of single embryos during the in-vitro fertilization procedure, according to interviews and industry data. Some doctors say that powerful financial incentives hold sway in a competitive marketplace. Placing extra embryos in a woman’s womb increases the chances that one will take. The resulting babies and word of mouth can be the best way of luring new business.

Doctors are also often under pressure from patients eager for children, who have incentives to gamble as well. Frequently, they have come to IVF as a last resort after years of other treatments, are paying out of pocket, and are anxious to be successful on the first try. And many do not fully understand the risks.

Dr. William E. Gibbons, incoming president of the American Society for Reproductive Medicine, said his organization was concerned about the risks of twin pregnancies and would issue new guidelines at a meeting next week to further discourage multiple births. “People should be made aware of the concerns that we think twins are not a good outcome,” Dr. Gibbons said.

The industry creates preterm infants with in-vitro and other fertility treatments even as government and nonprofit groups work to fight the nation’s 12.7 percent rate of prematurity, regarded as a major national health care problem.

While IVF multiples are typically the children of affluent women, much of the effort at reducing premature birth has been focused on prevention and prenatal care for low-income women. A study released last week by the March of Dimes cited fertility treatments as one of the main reasons for a 36 percent increase in prematurity in the last 25 years.

The government estimates that caring for premature infants costs $26 billion a year, including $1 billion for IVF babies, expenses that eventually get passed through the system and on to businesses and consumers.

The unusual birth of octuplets in California in January notwithstanding, the American Society for Reproductive Medicine and its affiliate, the Society for Assisted Reproductive Technology, have succeeded in reducing the number of larger multiple births from in-vitro fertilization over the last several years.

The two medical organizations and the federal Centers for Disease Control and Prevention have been promoting the use of single embryos in many cases to reduce the number of twins. But that has not translated into major action at the 483 fertility clinics across the country. The latest figures from the industry show that women under 35, the group most likely to get pregnant from the treatments, choose to use single embryos in only 4.5 percent of in-vitro rounds.

“You can’t convince a couple that having twins is a bad thing,” said Dr. Maurizio Macaluso, who runs the C.D.C.’s women’s health and fertility branch. “That’s a major communication problem.”

In 2006, a record 137,085 twins were born in the United States, double the number in 1980. Of that total, 23,284 were the result of IVF, according to government statistics. The number does not include twins born as a result of other fertility treatments.

Most fertility doctors acknowledge the potential problems with twins, whether conceived naturally or through fertility treatments. But many say that the good done by their industry — creating new families — outweighs the bad, and that twins are not such a risky bet because most are healthy.

“At the end of the day, when you dissect the statistics out, our patients are interested in establishing a family and a pregnancy,” said Dr. Michael Swanson, a Colorado fertility doctor who treated Ms. Mastera.

It is a tricky cost-benefit analysis, however, and one that potentially involves the worst kind of collateral damage, the type that figures in the nightmares of expectant parents.

Erin and Scott Hare of Houston lost their twin daughter, conceived through in-vitro fertilization. Her surviving brother, Carter, who was born at just over 24 weeks, is doing well but needs therapy for lingering problems.

George and Narine Nazaretyan of Van Nuys, Calif., have twin daughters conceived through IVF. One of the girls, Natlie, has a severe case of cerebral palsy, which occurs four to six times as frequently in twins as in single babies.

Cutting down preterm births from IVF would be an easy way to make a small dent in reducing the nation’s prematurity problem. Dr. Macaluso calls them “low-hanging fruit” — a partial solution that is within reach.

But there is concern among public health officials that the problem may instead grow as fertility treatments become available to more people.

“In the past few years, we have felt increasingly uncomfortable because we feel like we are sitting on the tip of the iceberg,” Dr. Macaluso said.

Pressure for Success

In the competitive marketplace for fertility medicine, success rates are the metric by which in-vitro clinics thrive or fail. The rates — meaning the chances of producing a baby at each clinic — are published by the C.D.C. and are widely used by couples to choose a doctor.

Congress passed a law in 1992 that required the data to be disclosed after some clinics were exaggerating their numbers to lure potential clients. But there is evidence that the law has had the unintended effect of pressuring doctors to transfer multiple embryos to maximize their success rates.

“If a person does not have as high a pregnancy rate as his neighboring competitor, they’re going to lose those prospective patients,” said Dr. David Kreiner, medical director of East Coast Fertility, a network of fertility centers based in Plainview, N.Y.

A busy fertility clinic can be extraordinarily lucrative, generating millions of dollars a year. And fertility doctors can take on godlike status in their communities for delivering their priceless commodities.

Knowing that prospective parents can easily seek IVF elsewhere, doctors give them unusual autonomy in deciding how many embryos to transfer.

For many in-vitro patients, the high cost of treatment is often a factor in making that decision. When Ms. Mastera had the procedure at Conceptions Reproductive Associates of Littleton, Colo., in September 2008, she was a candidate for single embryo transfer under industry guidelines. At age 32, and having never before undergone in-vitro fertilization, her chances for pregnancy were excellent.

Conceiving a child had become an obsession for the couple, who had met in 2000 while working as customer service representatives for Nextel. By 2006 they were married, living in a modest split-level home in Aurora and ready to start a family.

“I just told Jeff one day, ‘I think we should get off birth control; I’m ready,’ ” said Ms. Mastera, who was 30 at the time. “He was like, ‘O.K., let’s do it.’ ”

After trying unsuccessfully for more than a year, the couple consulted two fertility specialists in 2007 and spent more than $15,000 on the four rounds of intrauterine insemination.

“You’re an emotional basket case because you’re on these hormones,” Ms. Mastera said. “We’d be constantly worried about money. Like constantly. How are we going to pay our phone bill this month? Or our mortgage? Because we’re having to pay for all these fertility treatments.”

In-vitro fertilization was the next logical step, but the price tag was even more daunting. Depending on the clinic, its location and the extra services included in the treatment, the procedure can run $12,000 a cycle to more than $25,000.

In 2008, the Masteras consulted their third fertility expert, Dr. Swanson at Conceptions. They chose him partly based on his clinic’s high success rates as published by the Centers for Disease Control and Prevention.

Ms. Mastera’s insurance would cover about $8,000 for the procedure and drugs. Frequently, insurance does not cover anything. Almost $18,000 in clinic fees and other costs remained for the couple, who proceeded to cash out their 401(k) and money market accounts and put the remaining balance on a low-interest credit card.

Like many families, the Masteras could not afford a second cycle. So when the couple was given a choice by their doctor of implanting one or two embryos, they decided to increase their chances with two.

“This was our Hail Mary pass,” said Ms. Mastera, now 33. “We thought, let’s just do it. At the time, it was like, twins, they can be fun. They are fun, but holy cow.”

Some public health experts are frustrated by the disconnect between the medical risk of twins and society’s perception.

Twins are celebrities and celebrities have twins. The pop culture media goes into overdrive when stars like Angelina Jolie and Jennifer Lopez give birth to twins.

“When they have their twins, it’s a very acceptable thing,” said Dr. Frank L. Mannino, medical director of the neonatal intensive care unit at the University of California, San Diego, Medical Center. The center expanded the unit last year, citing increased demand for the services, largely because of the use of fertility treatments.

Dr. Alan R. Fleischman of the March of Dimes, which has begun distributing literature discussing single embryo transfer, said a result of playing down the risks of multiple births is that many women undergoing in-vitro prefer to have twins.

“It’s not just a matter of hoping that if you put two embryos in, you’ll get one baby,” Dr. Fleischman said. “There are many women who actually want to have two children and would like to have their full family with one pregnancy.”

The Risks

The problems began at week 24 of Ms. Mastera’s pregnancy.

The human uterus is designed to carry one fetus. An ultrasound on Jan. 7 showed that the extra burden of twins was placing pressure on her cervix, causing the amniotic sac surrounding Max to begin pushing through.

“I was really stunned; I couldn’t believe what was going on,” said Ms. Mastera, who had not been having symptoms. “They came in and said, ‘You are going into surgery right now.’ ” As doctors tried to comfort her, Ms. Mastera said, she began crying uncontrollably.

In a procedure called a cerclage, doctors pushed the sac back into her uterus, then stitched up her cervix.

“The doctor said that if she were pregnant with one, she would have been just fine,” said her husband, Jeff, 31. “The sheer weight of the babies was just pushing them lower and lower.”

After the procedure, Ms. Mastera was ordered to remain in bed at home. Doctors hoped she would make it close to her April due date. But on the night of Feb. 15, Ms. Mastera’s water broke.

Her boys were born the next day, and were not the healthy babies she had dreamed of. “They wheeled me in, after I had recovered for an hour,” she said. “And it was weird. They looked really frail and unhealthy.”

Ms. Mastera said she was aware of the risk of prematurity with twins and had discussed the issue with Dr. Swanson before having the in-vitro procedure. Informed-consent documents given to patients by fertility doctors normally detail the increased risk of twins. But even with those increased risks, the actual number of serious outcomes like fetal death or brain damage is small.

While the average single pregnancy in the United States now last about 39 weeks, the average twins are born at just over 35 weeks, , according to the Institute of Medicine. And there is emerging evidence that babies born at that time can develop learning problems.

“There’s increasing evidence that the 34-, 35-, 36-weekers, the bigger prematures — and there are large number of those — have significant problems with learning later on, even though their mortality isn’t high” said Dr. Richard E. Behrman, a pediatrician and former vice president and dean of medical affairs at Case Western Reserve University who led the institute’s committee on preterm birth in 2006. “And that’s not appreciated in the obstetrical and lay community.”

According to one federal study, about 30 percent of all twins end up in a neonatal intensive care unit. Twins are eight times as likely as single babies to be born at very low birth weight — defined as under 3 pounds, 4 ounces. These are the babies who often need the longest care and face the biggest problems. Dr. Macaluso calls them “million-dollar babies.”

Carter Hare, the son of the Texas couple, was one of them. His birth announcement in December 2006 gave a hint of the trouble: “Carter is born! 24 weeks 4 days.”

His health was touch and go. “They gave us a very grim outlook,” his mother, Erin Hare, said recently.

Doctors were aware early on that Ms. Hare’s pregnancy might be complicated. Three months before becoming pregnant with in-vitro twins she had miscarried a single in-vitro baby because of a condition called incompetent cervix, a problem similar to Ms. Mastera’s.

After becoming pregnant with the twins, Ms. Hare had her cervix stitched closed to keep her babies in place and remained hospitalized for much of the pregnancy.

At 20 weeks, an ultrasound showed that her baby girl’s heart had stopped beating, an apparent result of a compressed umbilical cord. “It was hard,” Ms. Hare said. “I actually at that point stopped accepting visitors. I put a ‘Do Not Disturb’ sign on the door.”

In her solitude, Ms. Hare was fighting to continue carrying both her son and the lifeless body of her daughter, whose sac began bulging through her vagina, threatening the entire pregnancy. Doctors performed a second cervical surgery, continuing efforts to keep her son from being born before 24 weeks gestation, regarded as the point of viability.

He was born four days beyond that milestone, 12 inches long and weighing one pound, 12 ounces. Carter spent 102 days in the neonatal intensive care unit at Presbyterian Hospital of Plano, near Dallas.

This year, Carter entered preschool.

“He’s really a little miracle baby,” said Ms. Hare, a tax accountant. The family has since moved to Houston. Despite initial heart and eye problems, Carter did not require surgery. He receives therapy for sensory problems that sometimes develop in premature babies.

“He wouldn’t like being in a pool,” Ms. Hare said. “He would scream. His senses are just off. He has an extremely high tolerance for pain, then sometimes he’s real sensitive. The whole sensory process, when they develop outside the womb, it just doesn’t develop. It takes longer.”

Despite her troubled pregnancy, Ms. Hare tried another round of in-vitro after Carter was born, this time undergoing a more invasive surgery that stitches the lower part of the uterus and the upper cervix together and requires an abdominal incision.

“A lot of people thought I was crazy, but I didn’t did feel our family was complete yet,” Ms. Hare said.

On April 29, 2008, a daughter, Lauren, was born by Caesarean section at 36 weeks, 4 days.

The Price Tag

In March, the United States Chamber of Commerce and the March of Dimes held a luncheon in Washington to discuss preterm babies. “The human costs are staggering,” Dr. Steven K. Galson, then the acting surgeon general, told the group. “The medical costs are staggering. That’s why we’re here.”

“Today you’re going to hear that preterm birth is not just a significant public health issue,” Dr. Galson said, “but that it also impacts businesses and employer health plans.”

The hospitalization and doctor’s care for Ms. Hare and her son exceeded $1 million. Most of that, about $750,000 to $800,000, was for Carter. The bill was picked up by the self-funded health plan of the Trammell Crow Company, the Dallas real estate investment company where Ms. Hare worked.

“The following quarter during the earnings release, somebody asked why there was a sharp increase in medical costs,” Ms. Hare said. No one identified her, but Ms. Hare knew that her family had contributed heavily.

In Atlanta, the Centers for Disease Control and Prevention hired an economist to predict what would happen if single embryo transfer were used in a large number of IVF cases.

Dr. Macaluso, the C.D.C. reproductive health official, estimates the patients, businesses and insurance providers would save more than $500 million annually, even taking into consideration the cost of extra in-vitro rounds, by lowering neonatal intensive care, special education and other costs of premature babies.

To reduce the number of twins, some clinics are experimenting with programs that provide IVF with single embryo transfer with free freezing of extra embryos and free transfer of frozen embryos if the first try does not work. Others are working to develop ways to identify the specific characteristics of a single embryo that will turn into a healthy baby.

Dr. G. David Adamson, a former president of the American Society for Reproductive Medicine, has advocated reducing the twins rate but says that the value of a baby should also be taken into account when discussing single embryo transfer.

“How many healthy babies do we want and what’s the risk and cost to the individual and society of having a baby with problems,” Dr. Adamson asked. “It’s a complex question, and varies from patient to patient.”

For the Masteras, the pain and anguish is fading as they watch their boys grow.

Although they are at risk for developmental problems because of their prematurity, the boys are meeting milestones. Max can now sit up on his own, and Wes crawled for the first time last week.

Ms. Mastera still feels guilty, worried that she did something to make her boys premature. “I don’t know if I’ll ever forget how horrible I felt about them coming early,” Ms. Mastera said. “And I don’t know if I’ll ever forget how we struggled.”