A Picture is Worth a Thousand Words
(to read the numbers, and you will want to read the numbers, left-click on the bargraph, then hover mouse over lower right corner till blue/orange box/arrows appears, then click that to enlarge)

Kahlenborn Meta-Analysis, Mayo
Clin Proc. 2006;81:1290-1302
That's a pretty readable graph The Polycarp Institute website has. This depicts the findings of their meta-analysis recently published by The Mayo Clinic Proceedings Journal.
Let me say that again, slowly: The Mayo Clinic.
Turns out the International Agency for Research on Cancer (IARC), the National Toxicology Program (NTP) and the Indiana University-Purdue University At Indianapolis Department of Environmental Health and Safety have also, since 2005, "classified oral estrogen-progestogen contraceptives [aka The Pill] as carcinogenic to humans (group 1 carcinogen)...which is a higher classification than the 1999 IARC evaluation."
Not exactly subjective, pro-life, "anti-abortion" sources, now, are they?
They conducted a meta-analysis of 39 independent case-control studies that had most cases diagnosed since 1980 to better evaluate the association with breast cancer in the context of more contemporary use patterns. Overall, they found that compared to never use, ever use of OCs was associated with a small but statistically significant increased risk of breast cancer...None of this is news to us, sadly; we've been writing about similarly published, vetted research for the past five years.
~James R. Cerhan, MD, PhD, Division of Epidemiology, Mayo Clinic College of Medicine
And Dr. Chris Kahlenborn of The Polycarp Institute, who the above Mayo Clinic editorial references, long has been dismissed as a pro-life, "anti-abortion" nut. I know. I've quoted Kahlenborn and linked to Polycarp, only to be roundly derided for doing so.
Kahlenborn et. al.'s conclusions?
Use of OCs is associated with an increased risk of premenopausal breast cancer, especially with use before FFTP (first full-term pregnancy) in parous ("having given birth one or more times") women....The association between OC use and breast cancer risk was greatest for parous women who used OCs 4 or more years before FFTP.I guess now that the Mayo Clinic has seen fit to peer-review and publish his latest meta-analysis study, people might stop discrediting him and his work. But I doubt it. The mass media won't tell anyone about this. I bet the Associated Press doesn't publish a drop of ink on it.
Full published study here: Kahlenborn C, Modugno F, Potter DM, Severs WB. Oral contraceptive use as a risk factor for premenopausal breast cancer: a meta-analysis. Mayo Clin Proc. 2006;81:1290-1302.
And check this out: Phyllis Wingo's two studies are included in their meta-analysis (Wingo et. al. found 26% and 27% increased risk of cancer from the Pill in women who took it prior to first pregnancy).
Recall that Wingo was the CDC researcher who studied and found that abortion increased breast cancer risk as well, that is, before she left the CDC and started working for the obstructionist American Cancer Society and doing an about-face on the A/BC link.
I really don't look forward to the day when all women wake up and realize how we've been kept in the dark.