In 1981, the first U.S. baby was born through in vitro fertilization. Scientists and doctors have come a long way since then. Today the procedure is more efficient than ever for families unable to conceive.
In addition to improving pregnancy rates and efficiency, doctors have found methods for decreasing the chance of multiple pregnancies. The number of miscarriages following IVF also has declined.
Decades ago that prospect would have sounded more like science fiction. Today, it's allowed couples with difficulty conceiving to have children with better success than ever before.
"We're able to compress a year's worth of trying into one embryo," noted Dr. James Grifo, director of the New York University Fertility Center."It will never work for all patients, but it certainly has helped a lot of families."
What is IVF?
In vitro fertilization (IVF) occurs when a woman’s egg and a man’s sperm are combined in a laboratory dish, with the actual fertilization considered to have happened when the sperm attaches and enters the egg. The term in vitro fertilization literally means “outside the body.”
In the U.S., the process has been used since the early 1980s to aid women in becoming pregnant, and is generally only used after other methods of conceiving have failed, in part because the process can be expensive and could require multiple attempts. Most commonly it is used to aid women who are infertile because of damaged fallopian tubes, or endometriosis, which occurs when the uterine lining grows into other areas of the body, according to the National Institutes of Health.
Women also may seek IVF when advanced age will not allow them to conceive naturally, or when their partner is affected by infertility.
Though IVF itself sounds simple, it is a process that includes several steps. Women begin the process by taking fertility drugs to increase egg production so that her ovaries will produce several eggs in one month instead of just one. Regular transvaginal ultrasounds to check the ovaries and blood tests to determine hormone levels also are required.
Then a physician will retrieve the eggs through a minor surgical procedure called follicular aspiration. Donated eggs may be used as an alternative in women unable to produce eggs.
Once the eggs have been gathered, insemination occurs by mixing the sperm with the highest quality eggs. The sperm may be directly injected into the egg in a process called intracytoplasmic sperm injection if it is suspected there is a low chance of fertilization.
After the fertilized egg divides, it is considered an embryo and laboratory staff will monitor it to ensure proper growth. In normal embryos, several cells will actively divide within five days. Those couples considered at high risk of passing on a hereditary disorder may opt for pre-implantation genetic diagnosis.
This occurs several days after fertilization. Scientists remove a single cell from each embryo and screen for genetic disorders, which can help couples decide which embryos to implant.
Within five days of the egg retrieval and fertilization, embryos are placed in the women's womb during a minor procedure in her physician's office. Often only one embryo is implanted but more may be used if deemed appropriate. Age is a factor that often plays into a decision to implant multiple embryos. If one or more embryos implants in the womb lining, a pregnancy results.
Success rates
A woman's chance of becoming pregnant through IVF varies widely depending upon the clinic selected, her age and other factors. More than 1 percent of all babies are now born through IVF, according to the U.S. Centers for Disease Control and Prevention.
Of about 62 million women of reproductive age in 2002, about 1.2 million, or 2 percent, reported an infertility‑related doctor appointment within the previous year and an additional 10 percent had received infertility services at some time in their lives, the CDC reports.
A 2009 CDC report concluded that of 102,478 IVF procedures started, 37 percent lead to a pregnancy. However only 30 percent of those pregnancies resulted in a live birth.
According to the Society of Assisted Reproductive Technologies, a woman under the age of 35 has the best shot at getting pregnant through IVF and giving birth to a live baby, with a success rate between 41 percent and 43 percent.
Women between 35 and 37 are up to 36 percent to give birth to a live baby, while women between 38 and 40 have a chance that is up to 27 percent and women over the age of 41 are 13 percent to 18 percent likely to give birth to a live baby after IVF.
"It has greatly improved since the 90s," noted Dr. Grifo. "Probably the top numbers have 60 to 70 percent of cycles making babies. It certainly will never be able to work for all patients."
Better selection
Dr. Grifo said that doctors have been able to successfully reduce the number of multiple pregnancies, yet increase the chance of becoming pregnant simply by limiting the number of embryos transferred. Physicians are able to transfer fewer embryos because they've found methods for better selecting an embryo that has more potential to cause a pregnancy.
"We're growing them longer in the lab so we can better select embryos that are more likely to result in a pregnancy more successfully," he said. "Traditionally we did the embryo transfers on day two. Then it went to the third day, and now we're on day five. We watch them develop and we're better able to select which one will make a baby."
In fact, much of the success simply depends on making the right embryo selection. He noted that not all embryos are good and that most eggs don't make good embryos.
"Success in IVF is about finding that one embryo that is chromosomally normal and also makes a pregnancy," Dr. Grifo said. "A significant percentage of patients are doing single embryo transfers, or maybe just two."
Dr. Grifo said that in addition to better selecting embryos more likely to result in pregnancy, doctors have also gotten better at screening out those likely to end in miscarriage, "which is a real insult."
Birth defect screening Vs. designer babies
Along with improved pregnancy success, physicians also have gotten better at screening out genetic disorders such as cystic fibrosis, Down syndrome or Tay Sachs disease. Previously the genetic screening, if performed, would be done on day five.
Now they've moved the screening date to day three, which has resulted in a stronger screening process, allowing them to weed out a larger number of embryos that could be chromosomally abnormal.
Though genetic screening allows couples to reduce their chance of a child with an inherited disorder, the rate of birth defects among IVF babies is very similar to those naturally conceived, at about 5 percent, many of which are considered minor defects.
"There's not a measurable difference. I don't know that IVF or anything will ever take away the risk of birth defects. I don't think we'll ever fully be able to screen out chromosomally abnormal embryos," said Dr. Grifo. "The incidence is so small so it's really not very different. Most problems with IVF really relate to multiple gestations and premature delivery."
The risk of a pregnancy that involves multiple babies is slightly greater for IVF, though the increase is not significant and has declined since IVF was introduced.
Another screening available is one that identifies the gender of an embryo. Dr. Grifo said that option is never offered for a first pregnancy, and is offered only when requested by parents for the purpose of gender balancing, such as when a family has three sons and is hoping for a daughter.
The genetic screening combined with the technology to select gender had prompted 90s term "designer babies," which Dr. Grifo called a "sexy media thing."
"We are so far away from being able to select for those kinds of genes," he said of the idea that would-be parents could genetically engineer a baby with particular genes or characteristics.
