During in vitro fertilization (IVF), physicians previously implanted multiple embryos; however, recent research has shown that the success rate of pregnancy with one embryo transfer is a viable alternative.
Basics of In Vitro Fertilization
There are five basic steps to complete a cycle of in vitro fertilization.
- Your egg production is stimulated with fertility medications.
- The eggs are harvested.
- The sperm is examined after collection.
- The sperm is combined with the eggs in incubators. In some cases, a single sperm may be injected into one egg in a process called intracytoplasmic sperm injection. These fertilized eggs are now called embryos.
- The embryos are placed in the woman's uterus from one to six days later.
Success of In Vitro Fertilization
The success rate of IVF depends on patient characteristics and treatment approaches. Successful implantation does not equal successful pregnancies though. Younger women tend to have a higher percentage of live births after IVF. Women under the age of 35 have a 30-35 percent live birth rate; women over age 40 have a live birth rate of 6-10 percent.
Complications of Mulitple Embryo Transfer
Implanting more than one embryo at one time has been a better way to ensure more successful pregnancies. Guidelines from the American Society for Reproductive Medicine recommend that reproductive endocrinologists transfer two to three embryos into women who were aged 35 to 37 and that three to four embryos are transferred for women who were 38 to 40 years of age. Transferring one embryo into women younger than 35 years tended to have more success.
Transferring multiple embryos at once increases the chance of multiples along with complications for the mother that may arise from having multiple babies, such as high blood pressure and gestational diabetes.
The babies born in multiple pregnancies are often at higher risk for complications after birth as well, including:
- Prematurity
- Low birth weight
- Breathing problems
- Problems with digestion
- Learning problems
- Developmental disabilities
These babies may also need to stay in the hospital for extended periods of time.
Single Embryo Transfer
Single embryo transfer (SET) has become more accepted over the past few years. Since most people who undergo IVF are paying for the procedures and medications out of their pockets, there is concern about failing to become pregnant; couples are often willing to risk the possibility of complications of multiples in order to have a successful pregnancy.
A study from 2008 showed that while transferring one embryo at a time may cost $100 million more up front but may save $1 billion in health care costs. When an infant is born prematurely, the medical care can cost hundreds of thousands of dollars.
Success Rate of Pregnancy with One Embryo Transfer
Several recent studies have shown that the success rate of pregnancy with one embryo transfer--even in women who were over 35 years of age--can be as successful as implanting more than one. In 2003, doctors in Australia found that transferring one embryo had the same rates of pregnancy when compared with multiple embryo transfer. Additional research from 2007 found that with women over 35 who had one high-quality embryo transferred had a rate of pregnancy twice that of women in that age group who typically undergo IVF.
In Europe, SET is more widely accepted than in the U.S. However, in more practices in the US, patients younger than 38 are now offered single embryo transfer and around 70 percent of them accept. The pregnancy rate for these women is around 40 percent.
Is SET an Option for All?
SET may not be a viable option for every woman who is undergoing IVF since the success rate of pregnancy with one embryo transfer may still be low. Women over 40 or women who do not have embryos of great quality may still have to undergo multiple embryo transfers to maximize their chances of pregnancy.
