Get familiar with these pregnancy statistics by age so can increase your odds of conceiving in your 20s, 30s, 40s and beyond.

If your period is the only time you pay attention to what goes on below your belt, you're not alone. For most women, trying to conceive is a huge question mark. Consider this your crash course in Reproduction 101.

First, let's start with the basics: You're born with 1 to 2 million eggs at birth, and those are all eggs you're going to have in a lifetime. By the time of your first period, your supply dwindles to 300,000.

"If a woman ovulates 500 times between the ages of 12 and 52, and if not all of those eggs are considered to be healthy, what you're left with is a select few eggs that are truly viable for pregnancy," says Alan Copperman, M.D., director of Reproductive Medicine Associates of New York and co-director of the Division of Reproductive Endocrinology and Infertility at The Mount Sinai Hospital in New York City.

Adding insult to injury, human reproduction isn't all that efficient. There is only one week in your cycle during which your odds are really favorable — and goodness knows that few of us can devote a whole week each month to nonstop boot-knocking in the name of baby making. It helps to know your odds of conception at every stage so you can make the most of them.

RELATED: Your Chances of Getting Pregnant Every Day of the Month

Early 20s (20 to 24)

Behold, the magic window for baby making! "[When a woman is] 21, 90 percent of [her] eggs are chromosomally normal, which helps your chances of conceiving a healthy baby," Dr. Copperman says. You also have age on your side — the average woman's fertility peaks at the age of 24.

Women under age 25 have a 96 percent chance of conceiving in a year if they're trying each month. If the guy is under 25, the odds drop to 92 percent. That's because many fertility issues among younger couples are on the man's side. Most are easily treatable and don't require help from a specialist unless conception is taking longer than one year.

Mid-late 20s (25 to 29)

From age 25 to 34, you have an 86 percent chance of conceiving after trying for a year. Your chances of miscarrying are 10 percent, only a little higher than they were in your early 20s. Keep doing what you've been doing and you'll be likely to have a baby within a year. There's no need to consult a specialist until you've been actively trying for more than 12 months without success.

Early 30s (30 to 34)

Your odds of conceiving are still high — up to an 86 percent success rate for couples that try for a full year. The only major change is that your chances of miscarriage by age 30 have risen to 20 percent.

Conventional wisdom says that you don't need to see fertility treatment in your early 30s until you've been trying for a year with no luck, but some doctors recommend consulting your ob-gyn or primary care physician if you're still having trouble after 9 months.

"That way, they can pinpoint any problems and treat them before your fertility starts to decline more rapidly after 35," Dr. Copperman says.

Mid to late 30s (35 to 39)

"You still have a good outlook for getting pregnant in this window, particularly before age 37," says Kelly Pagidas, M.D., a fertility specialist with Women & Infants Center for Reproduction and Infertility in Providence and an associate professor at Brown University Medical School. At 35, most women have a 15 to 20 percent chance of getting pregnant in a given month. That could mean a 78 percent chance of conceiving within the year.

But 35 seems to be the point where fertility does decline. "The most common reason is reduced egg quality," Dr. Pagidas explains. "You may have plenty of eggs to work with, but they're likely to have more chromosomal defects that affect their viability. You're also at a little greater risk of miscarriage, a Down syndrome pregnancy or an abnormal pregnancy."

Roughly 30 percent of women age 35 may take a year or more to conceive. Doctors don't want you to wait that long to find out if you're one of them. Time is of the essence, and if you're having trouble conceiving after six months, see a specialist to undergo some testing. Intrauterine insemination is a less invasive assisted reproductive technology that may work but in vitro fertilization (IVF) may be an excellent treatment option as well.

Finally, this is your last chance to freeze viable eggs for use at a later date, should you prefer not to get pregnant right now. "A woman can freeze her eggs up until age 40; then she can come back years later and have a good chance of pregnancy even into her mid-40s," says Steven R. Bayer, M.D., reproductive endocrinologist at Boston IVF fertility clinic.

Early 40s (40 to 44)

With advancing age, egg quality and quantity go down. At this stage, you're facing a few challenges that make it harder to conceive and to stay pregnant.

"By the time she's in her 40s, 90 percent of a woman's eggs are chromosomally abnormal," Dr. Copperman says. Assistance from reproductive technologies becomes more common at this time, and not just because of the egg issue. There may be more issues with older male partners, and some women report an increase in uterine lining issues with age. The uterine lining thins and blood supply to it decreases with age, making it more difficult for the egg to implant.

Women approaching menopause may also see their cycles shorten. (The onset of menopause is generally between ages 40 and 60.) "That means as the cycle shortens, ovulation occurs earlier in the cycle, as soon as day nine," Dr. Bayer explains. "You need to make sure you adjust the timing of intercourse around ovulation accordingly."

The rule of thumb at this age for natural conception is to have sex every other day around the time of ovulation. A good sign that you are getting close to ovulation is an increased production of a clear cervical mucus. An ovulation predictor kit may also help with the timing of sex. If conception is taking more than three months, see your doctor right away.

For women over the age of 40, conservative treatment with inseminations carries a low success rate. The best option is IVF. If a 42-year-old woman has five embryos placed, there is a 10 to 20 percent chance of pregnancy. (If pregnancy is achieved, there is a 20 percent chance of a multiple; this carries its own risks.) For women who have low ovarian reserve and produce only a few embryos, or for women over the age of 43, egg donation is the best choice.

45 and over

At 45, a woman's likelihood of getting pregnant is no more than 3 or 4 percent. That's not to say it's impossible, but assisted reproductive technologies are almost always necessary, with IVF the most common.

"The few eggs you have left may have chromosomal abnormalities, so screening before IVF is critical," says Dr. Copperman. Success rates are 0 to 1 percent, and most clinics recommend using eggs donated by a younger woman for those who want to conceive between ages 46 and 50.

For a woman in her mid-40s who wants to have a biological pregnancy, using a donor egg is best bet. "It's fairly easy for a healthy woman to achieve and sustain a pregnancy if the egg is from a healthy 25- or 30-year old," Dr. Bayer says. "Even if she's in menopause, success rates are about 60 to 65 percent."

How to Up Your Chances of Getting Pregnant at Any Age

Regardless of your age, you can maximize your chances of conceiving each month by figuring out exactly when you ovulate.

"Ovulation generally occurs 14 days before your next period, no matter how long your cycle is," says Dr. Bayer. For instance, if you have a 34-day cycle, you ovulate around day 20; a woman with a 26-day cycle would ovulate on day 12. Whatever your date of ovulation, plan to have intercourse in the five days prior to that day and for two days after.

"You'll know you're nearing ovulation when you start producing clear, slippery cervical mucus which starts one to four days before egg release," Dr. Bayer says. Another good predictor is ovulation kit. "When it shows you're getting ready to ovulate, have intercourse over the next two days to catch the fertile window. You have 24 to 36 hours to have sex to make it in the optimal window," Dr. Bayer explains.