Catholics have been doing this for ages with urine tests. Ignoring any morality whatever, this 'tech' is really old. People malign it as the 'rhythm method'.

Catholics have been doing this for ages with urine tests. Ignoring any morality whatever, this 'tech' is really old. People malign it as the 'rhythm method'. However, keep in mind that with the 'in-use' efficacy rate of 92%, about 1/12 couples using this method will fall pregnant in a year.