Statistics

There are so many variables to take into account when evaluating a programs' statistics, doctors and patients alike fall into the habit of comparing programs based on their statistics.

We feel that statistics alone are insufficient in properly choosing a program that is right for you. Statistics must be carefully evaluated or they may give a misleading impression about the true value of a program.

Understanding the process will help you understand the statistics and evaluate what is best for your and your family. A successful cycle of ART involves several steps:

1. Overriding the control of the ovary by the pituitary gland with a gonadotropin releasing hormone (GnRH) agonist. GnRH is the hormone which normally controls the release of two reproductive hormones -- follicle stimulating hormone (FSH) and luteinizing hormone (LH) -- from the brain.
   
   A derivative of GnRH is used to temporarily stop the release of FSH and LH from the brain. This is important because if the woman's ovaries receive conflicting signals from the prescribed hormones and those released by her own brain, her oocytes may ovulate prematurely and be lost.
2. Superovulation [recruitment of multiple oocytes with intramuscular injections of the pituitary hormones (FSH and LH)]
3. Retrieving the oocytes
4. Fertilization of oocytes and sperm in vitro
5. Transferring embryos into the uterus through the cervix
6. Supporting the pregnancy with supplemental hormones
7. Positive pregnancy test (chemical pregnancy)
8. Ultrasound showing an embryo with fetal heart motion (clinical pregnancy)
9. Delivery of a healthy baby at term

Each step is a hurdle that the couple must clear to reach the next step. Approximately 26 percent of couples (average female age 34) who begin a cycle clear all nine hurdles each cycle of ART. However, success rates may be quoted accurately using different numerators and denominators.

For example, look at the following program statistics:

• 100 couples come to the clinic to begin an ART cycle
• 90 are cleared to begin superovulation
• 80 stimulate well and go through an oocyte retrieval
• 75 successfully produce embryos in culture and receive an embryo transfer
• 35 get a positive pregnancy test and
• 26 actually take a baby home

According to these statistics, 26 percent of couples entering the cycle took a baby home and 47 percent of couples receiving an embryo transfer had a positive pregnancy test.

Both statistics are accurate. However, couples may mistakenly conclude that a program quoting the first statistic is less successful than another clinic that reports the second number.

In actuality, the first number is the most relevant to a couple who has not yet begun the process. Therefore, it is important for patients to understand the numerator and denominator used to determine pregnancy rates.

Additionally, the smaller the denominator, the more likely that the statistic may not reflect the long-term success of the program.

Other factors that play an important role in the success of assisted reproductive techniques are a patient's age, reproductive history, diagnosis, prior therapy (type and duration) and results of that prior therapy.

A 25-year-old woman who had her fallopian tubes removed for three recent ectopic pregnancies has a better chance of success than a 38-year-old woman who has completed five cycles of therapy involving superovulation that resulted in a poor ovarian response and no pregnancies.

Many programs have different criteria for initiation of infertility care as well as different thresholds for cancellation.

Our Statistics

Duke Fertility Center statistics from 2002 are currently available on the Centers for Disease Control’s Web site, as is information about interpreting infertility and in vitro fertilization success rates and the tables it publishes.

Since the end of 2000, we have stopped using blastocyst culture and day five or six embryo transfer as we found that it lowered our pregnancy rates, some of which is reflected in 2000's data.

We now perform all of our transfers on either day two or day three after retrieval. That said, we feel that our "numbers" compare favorably to those both in the area and nationwide.

SART

What is SART? The Center for Disease Control (CDC) and the Society for Assisted Reproductive Technology (SART) have compiled statistics from multiple centers. They require data be collected in a standardized format for presentation. This data is referred to as the "SART data" by most centers.