Kayla Bartsch makes some very good points in her NRO article earlier today, arguing that increased use of contraceptives does not always mean fewer abortions. The 2003 Guttmacher study she cites finds evidence of increases both in contraception use and abortion rates in multiple countries, including the United States. Bartsch is also correct that multiple studies show that approximately half of all women seeking abortions were using some kind of contraceptive the month that they became pregnant.
There is additional evidence bolstering her arguments. CDC data indicate that there have been significant increases in contraceptive use in the United States since the early 1980s. However, since that time the rate of unintended pregnancy has fluctuated. In fact, Guttmacher finds that the unintended-pregnancy rate increased between 2001 and 2008, a period when the percentage of women reporting contraceptive use was also increasing.
Furthermore, arguments about the efficacy of IUDs and other long-acting reversible contraceptives (LARCs) are overstated. The study on the St. Louis program that Bartsch cites relied on volunteers and did not have a control group. Since women who volunteered to take part in the program likely had above-average motivation to avoid pregnancy, that skews the results. Similarly, rigorous econometric analysis of a Colorado program to provide teens with LARCs showed a far more modest impact than what has been generally reported.
Bartsch is correct that the upcoming Supreme Court case involving the regulation of chemical-abortion drugs will likely increase the salience of contraception. Furthermore, many prominent Republicans, including Nikki Haley and Kellyanne Conway, have recently come out in support of policies that would make contraception more available. However, a body of research shows that policies to promote contraceptive use are either ineffective at best or counterproductive at worst. Overall, education, pro-life legislation, and assistance to pregnant women in need are far better strategies to reduce the incidence of abortion.