Could be, but b/c gestation takes 9 months breast feeding would only have to take place for 13 months for lactational amenorrhea to result in the 2 year spacing

Could be, but b/c gestation takes 9 months breast feeding would only have to take place for 13 months for lactational amenorrhea to result in the 2 year spacing. Based on a quick google search of breastfeeding rates, in the US 25% of women who breast feed do so until 12 months, which may be enough to create the difference noted in the study.