NFP is undeniably more complex to use than sterilization, but couples who are highly motivated to avoid pregnancy make charting and interpretation errors extremely rarely.

The study I discussed in the column you mention looked at NFP use by a diverse group of couples, in a first world country, whose reasons for and commitment to avoiding pregnancy almost certainly varied widely. The total unintended pregnancy rate for that study was just under 3%, but trials of NFP in which couples uniformly have very serious reasons to avoid pregnancy, such as [url=http://www.woomb.org/omrrca/bulletin/vol27/no4/chinaEvaluation.html]this trial[/url] in communist China and another conducted among predominantly very poor women in India* find much lower total pregnancy rates (5/1000 or 0.5% and 2/1000 or 0.2% respectively).

Even more significantly, however, in real life the 1/1000 pregnancy rate that you cite for sterilization simply does not hold true. Although user error is not an issue, there are differences in the way that surgical sterilization is performed and also in how an individual’s body responds to such surgery. In practice the overall pregnancy rates following surgical sterilization vary, but a quick search turned up pregnancy rates of up to [url=http://journals.lww.com/obgynsurvey/Abstract/1996/12000/The_Risk_of_Pregnancy_After_Tubal_Sterilization_.7.aspx ]36.5/1000 (3.65%) for tubal ligation [/url] and[url=http://www.ncbi.nlm.nih.gov/pubmed/12742564] )42/1000 (4.2%) for vasectomy[/url].

Yes occasional charting errors and, as a result, occasional unintended pregnancies are unavoidable with NFP even for highly motivated couples. Still, pregnancy after surgical sterilization is not nearly so rare as it is often assumed to be and careful, conservative use of NFP can definitely be comparable in terms of effectiveness.

*This study does not appear to be available online, but the citation is Ghosh Ak, Saha S., Chattergee G.. Symptothermia vis-a-vis fertility control. J Obstet Gynaecol Ind 1982; 32: 443-447

The study I cited in the column you mention looked at NFP use by a diverse group of couples, in a first world country, whose reasons for and commitment to avoiding pregnancy almost certainly varied widely. The total unintended pregnancy rate for that study was just under 3%, but trials of NFP in which couples uniformly have very serious reasons to avoid pregnancy, such as [url=http://www.woomb.org/omrrca/bulletin/vol27/no4/chinaEvaluation.html]this trial[/url] in communist China and another conducted among predominantly very poor women in India* find much lower total pregnancy rates (5/1000 or 0.5% and 2/1000 or 0.2% respectively).

Even more significantly, however, in real life the 1/1000 pregnancy rate that you cite for sterilization simply does not hold true. Although user error is not an issue, there are differences in the way that the surgical sterilization is performed and also in how an individual’s body responds to such surgery. In practice the overall pregnancy rates following surgical sterilization vary, but a quick search turned up rates of up to [url=http://journals.lww.com/obgynsurvey/Abstract/1996/12000/The_Risk_of_Pregnancy_After_Tubal_Sterilization_.7.aspx ]36.5/1000 (3.65%) for tubal ligation [/url] and[url=http://www.ncbi.nlm.nih.gov/pubmed/12742564] )42/1000 (4.2%) for vasectomy[/url].

Yes occasional charting errors and, as a result occasional unintended pregnancies, are unavoidable with NFP even for highly motivated couples. But pregnancy after surgical sterilization is not nearly so rare as it is often assumed to be and so the two do remain comparable in terms of effectiveness.

*This study does not appear to be available online, but the citation is Ghosh Ak, Saha S., Chattergee G.. Symptothermia vis-a-vis fertility control. J Obstet Gynaecol Ind 1982; 32: 443-447

I’m not sure I understand how you’re arriving at this conclusion. You state elsewhere that 2/1000 women will conceive despite correct charting, and 3/100 will conceive due to charting errors. The failure rate of sterilization is about 1/1000, so strictly speaking, perfect-use NFP is about twice as likely to result in a pregnancy as sterilization (although the two are roughly on the same order of magnitude).

More important, though, is that 3/100 typical-use pregnancy rate. I don’t think it’s fair to just hand-wave that away and assume nobody will ever have charting mistakes. Obviously, the people who made those errors didn’t realize they were making them at the time. — it’s not like they deliberately decided to make a charting mistake, the way one chooses whether or not to use barrier birth control or take birth control pills. NFP is undeniably more complex to use than other forms of birth control, and some errors will be unavoidable.

Sterilization, by contrast, has no typical-use discrepancy. In actual practice, significantly fewer women will become accidentally pregnant with sterilization vs NFP. It may be worthwhile for other reasons, but I’m not sure it’s completely honest to claim it’s as effective as sterilization.