IUI is an easy and inexpensive treatment compared to IVF.
Many couples would like to try IUI first but don’t want to waste time either. Some
men have better sperm numbers than others. This question comes up often at IVF1, where I practice.
All other things being equal, how many moving sperm do you need for IUI to be successful?
First, some basics. In order to inject sperm into the uterus, it first has to be prepared.
This is sometimes called a sperm wash though that is a bad name. We are not actually washing the
sperm. What we are doing is separating the sperm from the ejaculated fluid and concentrating the
sperm into a small volume. I am going to refer to this process as the sperm prep.
In order for IUI to work, there must be sperm that can swim up into the fallopian tubes where
fertilization happens. Fertility doctors can calculate the number of moving sperm
both before and after the sperm prep is performed. Calculating the number of moving
sperm before the sperm prep is performed is not very helpful in predicting the success of the IUI
unless the numbers are truly horrible. Most studies have focused on the number of moving sperm
after the sperm prep. We call this the total motile sperm count or TMSC.
Research on this topic has been limited because studies involved small numbers of women or
researchers combined data from different fertility centers with different patient populations and
protocols. Recently, however, a larger study from a single fertility center in the USA
looked at this problem and was able to come up with some more definitive conclusions..
This study looked at over 92,000 insemination cycles from 37,500 patients. This makes it the
largest study ever published on this topic. The patients studied were typical of a modern
infertility practice. About half of the IUIs performed were in patients under the age of 35
and half were older. As you can see, IUI pregnancy rates were lower as women got older.
This finding is not surprising. The success rates for all fertility treatments decline with female
age. The patients in this study also took fertility medications. Women who
took injections of fertility medications such as Follistim had higher pregnancy rates compared to
women who took the oral medication, Clomid. Women who did a combination of clomid and
injections did not do any better than women who took clomid alone. The chance for pregnancy
was similar whether women were doing their first IUI, their 3rd or even their 6th IUI.
What about sperm numbers after the sperm prep.? This study found that the optimal number of
moving sperm was 9 million or higher. Couples who had sperm numbers in this
range had the highest pregnancy rate - just over 16% of couples became pregnant with each
attempt in that range. Their analysis determined that having a higher number of moving sperm,
like 18 million, didn’t produce any more pregnancies. In other words,
once you got over 9 million motile sperm, the pregnancy rates maxed out.
If the number of moving sperm was lower than 9 million, however, pregnancy rates started going
down. This was a gradual decline. There wasn’t any particular number where the pregnancy rate really
dropped off. The lower the number of moving sperm, the lower the chance for pregnancy. Even the group
with the lowest number of moving sperm, less than 250,000, still had a pregnancy rate of about 4%.
Our InfertilityTV bottom line is this, regardless of age, your best chance for IUI to succeed
happens when the total motile sperm count after the sperm prep
is 9 million or more. IUIs are going to work better when women are younger and if they use
injections of fertility medication compared to Clomid. Even couples with very low numbers of
moving sperm can still see pregnancies happen so its not futile to try but the lower the number,
the lower the chance for success. This is not the case with IVF, by the way. IVF works well
even when there are very few sperm because of a technique called ICSI where we inject 1 sperm
into 1 egg. Instead of needing millions of sperm, a handful will do the trick.
Finally, attempting IUI up to six times also seems reasonable as the percentage
of couples getting pregnant on their 6th try was as good as it was on the first try.
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