A mom's guide to birth control

Question: I've always been on the Pill, but now I'm breastfeeding. That means I can't go back on it, right?

Answer: Not necessarily. The main thing to avoid is contraceptives that contain estrogen, which can reduce your milk supply. So women who are exclusively breastfeeding need to steer clear of birth-control pills that contain both estrogen and progestin, as well as the Patch (a bandagelike square that delivers hormones into your bloodstream) and the Ring (which you insert into your vagina, where it releases hormones).

Instead, you could use a "mini-Pill" -- a progestin-only contraceptive, such as Micronor, that won't affect milk supply. (One caveat: It's important to take the mini-Pill at the same time every day for optimal effectiveness.)

You can also safely use an intrauterine contraceptive (IUC) or try any barrier method, such as a diaphragm, cervical cap, sponge, condom, and Leah's Shield (a reusable rubber insert), says Karen Meckstroth, M.D., assistant clinical professor of obstetrics and gynecology at the University of California, San Francisco. Parenting.com: Breastfeeding as birth control?

Q: I'm not sure whether I'm done having babies, so what's long-term but not permanent?

A: An IUC is ideal, and there are two types. The first, the Mirena IUC, releases a steady stream of progestin and is the most popular birth control with female ob-gyns.

It's even more effective than tubal ligation if it stays in place, says Dr. Meckstroth. It most likely works by changing the texture of cervical mucus so that it blocks sperm from reaching the eggs. It can also prevent ovulation. It's approved for up to five years, and once it's removed you can get pregnant right away.

There's also ParaGard, an IUC that's approved for up to 10 years and doesn't use hormones. It releases copper instead, which experts think creates an environment that's toxic to sperm. It may also keep the egg from attaching to the uterus.

Another option: Implanon, a matchstick-size rod that's implanted under the skin of your arm to release progestin and lasts for up to three years. One downside: It often causes breakthrough bleeding, so you'd have to be willing to put up with that. Parenting.com: When birth control masks infertility

Q: I've heard there's a type of sterilization for women that isn't surgical. Does it work? Is it permanent?

A: It's called Essure, and it's put in via a nonsurgical procedure that can be done in your doctor's office. A pluglike coil is inserted through your cervix into each fallopian tube. Over time, tissue grows over the devices, permanently blocking the tubes and keeping sperm out. Until the tissue is fully formed, you can't rely on it, so you'll have to use a backup method the first three months post-insertion. It seems to be as effective as tubal ligation and has a faster recovery, but its efficacy hasn't been studied beyond 10 years. You should also assume it's not reversible, says Daniel Mishell, M.D., chairman of obstetrics and gynecology at the Keck School of Medicine at the University of Southern California, in Los Angeles.

Q: I want to get pregnant fairly soon. What method should I choose?

A: The only option you should avoid is the Depo-Provera injection, according to Alison Edelman, M.D., an assistant professor of obstetrics and gynecology at Oregon Health Sciences University, in Portland. With Depo-Provera, you'll have to think about birth control just every three months, when you'll see your doctor for the pro-gesterone-only shot. "But it can delay fertility for up to a year and a half," says Dr. Edelman. (The average is six months.) With the other hormonal methods, including the Pill, it's possible to become pregnant within one to three months. Parenting.com: How to get pregnant -- again

Q: I'm single again and thinking about dating. Besides having a partner wear a condom, do I have any other options to protect myself from sexually transmitted diseases (STDs)?

A: Male condoms are still your best bet. And opt for those without the spermicide Nonoxynol-9. It's the condom itself that protects against conception (83 percent of the time) and nearly all STDs, which are now commonly called STIs (sexually transmitted infections). The tiny amounts of Nonoxynol-9 don't really improve protection against pregnancy or infections, and can be irritating. The other option is the female condom, which is similarly shaped but designed to be inserted into a woman's vagina; it has a flexible ring that holds it in place. It's 73 percent effective in preventing pregnancy and offers some protection against STIs, but it isn't as protective as the male condom.

Q: The Pill always made me nauseated. Do the Patch and the Ring have the same side effects?

A: Although all three contain estrogen, the hormone responsible for your nausea, studies show that the Patch delivers the highest dose. (The Patch has also been linked with an increase in blood clots; its makers now warn of this risk on the product label.) The Ring delivers the lowest dose of estrogen at a steadier rate, so it's your best best. Parenting.com: Can the Pill boost fertility?

Another alternative: a lower-dose Pill. Consider asking your physician to prescribe a brand that has the least amount of estrogen, like LoEstrin, Alesse, Mircette, or Ortho Tri-Cyclen Lo. Or try the new Loestrin 24 Fe or YAZ, which spread out a low dose of hormones over 24 days instead of 21. Then be patient. The nausea usually goes away after about three months, when your body gets used to the medication. Keep in mind, however, that low-dose options may not be as effective if you're overweight.

Q: At 36, am I too old for hormonal birth control?

A: No. It's considered safe for women over 35, as long as you don't smoke and aren't at high risk for heart disease. In fact, a growing number of ob-gyns actually recommend hormonal birth control right up until menopause. "Research shows that the Pill protects against ovarian cysts and ovarian, uterine, and colorectal cancers," says Dr. Meckstroth. Women who have been on the Pill for 10 years reduce their risk of ovarian and uterine cancer by 80 percent. Other forms of hormonal contraception likely offer similar protection against cancer.

Q: Is it safe to take birth-control pills that reduce the number of periods I get or stop them altogether?

A: There's no health benefit to a regular monthly period, says Mark DeFrancesco, M.D., chief medical officer at Women's Health Connecticut, so these pills -- including Seasonique, Loestrin 24 Fe, and Yaz -- are just as safe as traditional hormonal birth-control pills (which stop you from ovulating and mimic a monthly period).

However, many women prefer to continue getting a regular period because it reassures them that they're not pregnant.

For some women, though, having fewer, or no, periods is a good option -- especially for those who regularly experience heavy periods, menstrual migraines, or painful cramps. But keep in mind that some of the pills that eliminate or decrease the frequency of periods might cause breakthrough bleeding, an annoying side effect that may or may not go away in time.

Q: I'd like to use "fertility awareness" as my birth-control method. How can I be sure I'm doing it right?

A: By paying careful attention to detail. With perfect use, various forms of the "rhythm" method -- including charting basal temperature, monitoring cervical mucus, and noting cervical position -- can be up to 94 percent effective in preventing pregnancy. But with typical use, that number drops to only 75 percent. So consider taking a class in natural family planning -- many Catholic hospitals offer them. Your odds of success are greater if you combine more than one of the methods, which track a variety of signals. And the more familiar you become with your cycle, the less likely you are to have sex during the riskiest times of the month. Parenting.com: Do you know when you're fertile?

If your religion permits it, use a backup method for the first few months until you learn when your most fertile days are. Similarly, you can use a different method during the first six months postpartum, or until your periods become regular again.

Q: My husband got a vasectomy after our first child, but now we want to have more. Is it really permanent?

A: It can be reversed, but it's pricey (from $6,800 to $13,000) and the success rate is only 30 to 40 percent. Another option to consider: A physician can use a needle to remove sperm from the testicles and then perform in vitro fertilization. E-mail to a friend

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Dana Sullivan is the coauthor of "The Essential C-Section Guide."