of the pill (with monthly periods). The economic costs of having monthly periods with migraines, severe cramping, etc., preventing a woman from working, as well as the health risks of taking over-the-counter pain killers to deal with these "side effects" also must be thrown into the equation. (With nuvaring, a woman could really just leave it in for the full 28 days so no additional sales to the manufacturer - there is a published study showing it releases an effective amount of hormones to prevent pregnancy for at least 35 days - although this would not be recommended by the manufacturer). Some doctors suggest using the Seasonale routine: a period every 3 months. I believe Dr. Leslie Miller is in the process of conducting a study that examines using nuvaring continuously (such use is currently off-label, but prescribing regular BC pills for such off-label usage is very common).
What is "natural" depends on your perspective.
Evolutionarily, human bodies have evolved to deal with periods of famine (during which women will usually not ovulate (or menstruate) due to too low body fat) which is effectively birth control; although breast feeding is (by far) not a perfect form of birth control, on a population level, you do see lower rates of pregnancy amongst lactating women. Thus, it's not "natural" to take hormones (pills/patch/nuvaring/implanted rods) for birth control, but it's also not "natural" for women to have monthly periods for 35 or more years. (Evolutionarily, it's only fairly recent that most humans even lived for 35 years).
"Safe" is also a relative term. Pregnancy has its risks; it seems to protect against certain types of cancers, but may increase the risk of others. Hormones (pills/patch/nuvaring/implanted rods) used for birth control purposes have their risks (and are not recommended for women with certain health problems), seem to protect against some cancers and may increase slightly the risk for others, but the majority of American women accept the health risks (and benefits) to avoid getting pregnant while having sex. (See below for the *real* women why the pill was originally designed to be 21 days on/7 off).
"What's natural is for women between the ages of 16 and 45 to be not bleeding because they're pregnant or breastfeeding (or both) nearly all the time. Giving birth is the primary biological goal of the female body and without modern contraceptives women would be having a lot more babies and a lot less bleeding. Women in 1900 had around 150 periods in a lifetime; women today have closer to 450."
http://www.thestranger.com/seattle/Content?oid=15631... and from the same article:
In 1960, the FDA approved the first birth control pills, developed by John Rock--a devout Catholic and a professor at Harvard. His method, which opened up a new world of sexuality for millions of women, used naturally occurring female hormones to trick the body into thinking it's already pregnant--thus no ovulation, no chance of pregnancy. Initially, the drug was designed, like nearly all others, to come in a bottle; women would take one a day. "In view of the ability of this compound to prevent menstrual bleeding as long as it is taken," Rock's co-developer, Gregory Pincus, wrote in 1958, "a cycle of any desired length could presumably be produced."
But because of Rock's ultimately fruitless hope of receiving the Catholic Church's approval of the pill, he and Gregory Pincus came up with the three-weeks-on, one-week-off method--for purely cultural, not medical, reasons. Natural hormones, natural cycles, women still suffering their biblically mandated punishment for Eve eating the damn apple--why would the Church have a problem with that?
Birth control pills come in packs of 28, but only 21 of the pills contain hormones. The other seven are blanks. It's easier to remember to take a pill if you do it every day, and forgetting to take one means, obviously, you're more likely to get pregnant. But that's not the only reason for the week of sugar pills. Rock wanted to create birth control for the faithful and he hoped that by using natural hormones--already in the female body--and maintaining natural cycles, he could get the pope's approval. The Church had already allowed the rhythm method, which doesn't seem like much now, but it was an acknowledgment that Catholics could try to avert some pregnancies. The key was that the rhythm approach was deemed "natural." So-called artificial methods were never allowed--condoms and diaphragms blocked the eager sperm, and vasectomies and tubal ligations snipped what god had created. In fact, the Vatican did allow the pill until 1968 as long as it was taken primarily to cope with physical problems, such as painful periods, and the birth control was a secondary effect. I'm sure plenty of good Catholic women felt some pretty intense cramps during the '60s.