At what age is there the greatest gender disparity in healthcare spending?

One of the issues that I've seen crop up with semi-regularity in this US election cycle is talk of gender-disparity in the rates charged for health insurance down there. CNN noted the following:

New research by the National Women's Law Center released Monday shows that, in states that have not banned gender rating, 92% of the top plans charge women more -- despite the fact that the vast majority of them do not cover maternity services.

I would have tended to assume that pregnancy would indeed account for the greatest difference in healthcare, but that appears to be false. What do you find if you look at data on the subject? Though women on average spend between more healthcare dollars at all ages excepting under 18:

... the greatest disparity in health care spending between men and women was in the population aged 45 to 64 years. In this age group, the median annual per capita expenditures for women were approximately 50% greater than for men ($2,871 vs. $1,849).

That's not an age range that many women become pregnant at. Even if maternity services aren't covered, insurers would seem to have a genuine reason for charging women higher rates. To quote the CDC:

... excluding pregnancy-related visits, women were 33 percent more likely than men to visit a doctor, although this difference decreased with age. The rate of doctor visits for such reasons as annual examinations and preventive services was 100 percent higher for women than for men and medication patterns differed significantly.

In Canada auto insurers are allowed to charge young men higher rates do to having a bona fide reason for this. A ruling by the EU a few years back that gender-discrimination in auto pricing had to end wasn't exactly met with a lot of enthusiasm by some - prompting headlines like Car insurance: why women face £300 rise in premiums.

Is it fair to charge women more for health insurance? Is it fair to charge men more for car insurance? ... or for life insurance? ... or to pay out at higher rates on annuities held by men? How do you deal with the reality of pregnancy? Could you, e.g., spread the costs of maternity coverage across the whole population but allow insurers to account for other gender-differences in healthcare costs? Should you ban gender-based pricing for all forms of insurance?