Why does IVF fail? or
What factors affect the success of IVF?
Introduction
These are really loaded questions! Hopefully by the time the reader
reviews the information below they will have an understanding of the
multitude of factors that may influence the outcome. I have basically
separated the topics as follows:
- Patient Selection
- Stimulation Protocols
- Egg and Embryo Factors
- Embryo Transfer Technique
- Immune Factors
- Sperm Factors
- Factors in the Lab
Below each topic will link to a sub-page with
more information.
Unfortunately, not all patients conceive with their 1st IVF procedure.
More than one embryo is transferred, in general, in order to improve the
chances. The pregnancy rates plateau at 2-3 embryos transferred based on
age and the addition of more embryos only increases the multiple pregnancy
rate. In many ways, IVF is a lot like fertile couples attempting to
conceive. The chances to get pregnant are consistent each month up to 4 or
5 cycles. As you may know, the chance to conceive each month when couples
are completely fertile is about 20 % (Figure 1). Thus, it may take several
months to conceive even under the best of normal circumstances. Patients
undergoing IVF may need more than one try as well because of the
cumulative nature of conception. The pregnancy rate per cycle in much
higher than normal pregnancy when IVF is done because we put more than one
embryo in the uterus, in general. It is very common to learn a lot about
the failed cycle by reviewing the stimulation flow sheet and embryo report
with the patients and arrive at a different protocol that will be more
successful. We often will change a number of factors as we improve the
protocol to have a greater chance for success.
Figure 1. Cumulative pregnancy rate in healthy fertile couples
Months attempting
When we have looked at
our program’s pregnancy rates with IVF approximately 50% overall conceived
with the 1st try, 50% with the second try, and 50% the third try, and
about the same with the 4th try. Obviously it is very difficult to do
multiple IVF cycles, emotionally and financially, but it reassures us that
the chances to not change for the 1st several cycles.
Factors affecting IVF outcome
There is no doubt that IVF helps to diagnose problems of fertilization
and embryo development that could not be assessed by any other method. It
is both a diagnostic and therapeutic procedure. The complexity of human
reproduction means that many factors may play a role in the success or
failure of IVF.
In order to gain some understanding of the factors that may affect the
outcome of IVF, I will try and to dissect the IVF procedure to see which
factors are present which may affect outcome.
- Patient Selection
a. Age
b. Diagnosis; male and female
c. Ovarian reserve
d. Smoking
e. Other pre-IVF evaluations; HSG, SIS,
anti-sperm antibodies, acrosome reaction
- Stimulation Protocols
a. General Stimulation Flow Sheet
b. Long vs. Short Lupron
c. Antagonist
d. FSH vs. HMG
e. Premature Luteinization
f. Fluid in cavity during stimulation
- Egg and Embryo Factors
a. Number of eggs
b. Fragmentation
c. Embryo growth
d. Immature eggs at retrieval
e. Fractured zona
f. Polyspermy
- Embryo Transfer Technique
a. Day 3 transfer
b. Blastocyst transfer
c. Trial transfer
- Immune Factors
- Sperm Factors
a. Balanced translocations.
b. Y-Chromosome micro deletions.
c. Cystic Fibrosis mutations.
d. DNA fragmentation
- Factors in the Lab
a. Air quality
b. Temperature
c. Light
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