July 1, 2008 -- We've come a long way since the first "test tube" baby was born in 1978. Now, researchers are looking at how to predict whether women will become pregnant from in vitro fertilization.
Researchers led by Stanford University Medical Center assistant professor of obstetrics and gynecology Mylene Yao, MD, found a 70% accuracy rate in predicting whether a woman who has undergone IVF will become pregnant.
In vitro fertilization (IVF) involves combining eggs and sperm outside the body. There are various steps involved in combining the egg and sperm during IVF; ultimately an embryo is created and transferred into a womb. These steps are called cycles.
The researchers examined 665 cycles of in vitro fertilization in women under age 45. Some 4,144 embryos were created.
Typically, each IVF cycle produces five to 12 embryos.
Here are four factors that Yao and fellow researchers found to be the strongest predictors of pregnancy:
- Total number of embryos.
- Number of 8-celled embryos. Researchers look to see if embryos have 8 cells, making them developmentally sound.
- Percentage of embryos that stopped dividing and died.
- The level of the woman's follicle-stimulating hormone or (FSH). This hormone estimates how well the ovaries are working.
The researchers also found that these four factors were better at predicting pregnancy than any single factor gathered from the embryo(s) that was planted in the uterus.
Factors to consider during IVF:
- A woman's age.
- The quality of her eggs.
- Certain characteristics of each embryo. For instance, researchers found that it was important to look at the qualities of all the embryos, not just one.
The study's lead author says although there is not a test to gauge a successful IVF, the results may help shed light on what can be an agonizing and emotional procedure: "The information isn't yet customized to the individual patient," Yao says. "And what patients really want to know is: 'What is my chance of getting pregnant?'"
"If you talk with IVF patients or doctors, they wouldn't be surprised" to hear that the quality of all embryos in a cycle -- not just the transferred one -- matters, Yao says. "But it's important to go beyond intuition and to prove it scientifically, in order to move the field forward."
In a paper written alongside the study, the authors write that "hundreds of thousands of human embryos" are produced by IVF every year with "the vast majority" of them not thriving to become a live birth.
Yao said her team is working on a follow-up study that involves four years of data and uses live birth, rather than a positive pregnancy test, as the outcome.
The study appears in the July 2 issue of PLoS ONE.