Yes or No?
With information to support your answer of course :)

I was always led to believe no, but have come across various things
online which say it is in fact a risk.
I am not sure if these people were possibly getting mixed up with
regular birth controls containing estrogen.

Is there a big difference in the different types of mini pills? 

Thankyou.

Hi papil-ga -

I can understand your frustration in seeing mixed messages on various
websites.  I used as my authority,  two US government sources to get
an answer to your question.

YES OR NO? 
On two highly reliable websites--those of the National Institutes of
Health (NIH) and the Food and Drug Administration (FDA)--blood clots
are not among the listed side effects from the progestin-only pill
(POP).

Note that they do not explicitly say "unequivocally NO" to blood
clots; however, not listing them means that they have not been
reported in the clinical studies for the pills.  This is as close to a
NO that you are going to get from a scientific source.

The list of common, not serious, side effects listed by the NIH are:

    * irregular menstrual periods
    * headache
    * breast pain
    * upset stomach
    * dizziness
    * acne
    * increased hair growth

Some serious side effects caused by the POP:

    * bleeding that lasts a long time
    * lack of menstrual periods
    * severe stomach pain

http://www.nlm.nih.gov/medlineplus/druginfo/medmaster/a602008.html#side-effects

Additionally, as part of the approval process for the drugs (1995),
the FDA listed menstrual irregularity as the most frequently reported
side effect of the POP. They also mentioned "headache, breast
tenderness, nausea, and dizziness" as being reported in some studies.

The FDA did not list blood clots as a side effect.

http://www.fda.gov/medWatch/SAFETY/LABEL/guidance.htm

DIFFERENCES? From the information I've seen, all currently approved
brands are the same with respect to side effects (and reliability).

The NIH information covers the following brands:

    * Micronor®
    * Nor-Q.D.®
    * Ovrette®
    * Plan B®

http://www.nlm.nih.gov/medlineplus/druginfo/medmaster/a602008.html#brand-names

The FDA information presumably covers all approved brands.

Both websites stressed the need to take the POP on a strict schedule. 
Delaying the dose by only 3 hours reduces the mini-pill's
effectiveness and may mean failure. In the case of a missed dose,
backup contraception should be used for 48 hours.

http://www.nlm.nih.gov/medlineplus/druginfo/medmaster/a602008.html#if-i-forget 

In addition to the above sites, here is a good overview of
contraception on this university health center website:

http://www.stanford.edu/group/SHPRC/ch6_hor.html

To sum up an answer to your YES or NO question, I'd say this: "as far
as anyone knows to date, the answer is NO."
 
With this information, I know you'll be able to make an informed choice. 

Good luck and all the best,

alanna-ga

This reminded me of a story I saw on tv, on Dr. G., medical examiner.
A guy wakes up and his wife doesn't sound good. He gives her
mouth-to-mouth and notices a bad odor. It turns out that her bowel had
died, due to a clot from birth control pills.