Slideshow: Ovulation & Fertility - Facts to Help You Get Pregnant

Understanding Your Monthly Cycle

Knowing your menstrual cycle improves your chances of getting pregnant. The first phase starts with the first day of your period or blood flow. Your body releases hormones that stimulate eggs to grow within follicles inside your ovaries. Between day 2 and 14, those hormones also help thicken the lining of your uterus to get ready for the implantation of a fertilized egg. This is called the follicular stage.

What Happens During Ovulation

The average menstrual cycle is 28-32 days. While the exact timing of ovulation can vary, on average it happens between day 11 and 21 of your cycle. A brain hormone called luteinizing hormone (LH) surges, triggering the release of the egg that's most ripe. At the same time, your cervical mucus changes to a slippery, egg-white consistency, to help sperm make their way to the egg.

It's All in the Timing

Women are born with about 1-2 million eggs, but only 300 to 400 will be released through ovulation. Usually just one egg is released each month. The egg travels down the fallopian tube toward the uterus, where it's ready to be fertilized. The egg only lives about 12 to 24 hours after leaving the ovary. Sperm can live for about 3 to 5 days, so knowing you're due to ovulate soon can help you and your partner plan sex for when you're most likely to conceive. If fertilization does not occur, the egg dissolves after 24 hours.

Tracking Your Most Fertile Days

Generally, the highest chance of pregnancy is when intercourse occurs 1-2 days prior to ovulation. If you have a regular 28-day cycle, count back 14 days from when you expect your next period to start. Plan on having sex every other day around that time -- say, days 12 and 14. Keep in mind that having sex every day may decrease a man's sperm count. Your cycle may be longer or shorter, so using an online ovulation calculator may help identify the likely day.

Tracking Ovulation By Temperature

After an egg is released, what's left of the follicle, called the corpus luteum, releases the hormone progesterone to help thicken the lining of the uterus in preparation of pregnancy. Progesterone causes your body temperature to go up slightly. Taking your temperature every morning with a basal thermometer (about $10 at drugstores) before getting out of bed is one way to predict whether ovulation has occurred. It's inexpensive but not as accurate as other methods for tracking ovulation.

Predicting Ovulation by Hormone

A surge in LH is what triggers the egg to be released from your ovaries. Using ovulation kits (from $20 to $50) to check LH levels in your urine can help you pinpoint the day of ovulation. Some kits allow you to test daily to determine when you are ovulating. These kits are convenient and are 99% accurate.

The Last Phase Of Your Monthly Cycle

During the second half of your menstrual cycle, progesterone causes the lining of your uterus to thicken in preparation for a fertilized egg to implant. If the egg isn't fertilized and implantation does not occur, it disintegrates, progesterone levels fall, and about 12 to 16 days later, the egg -- along with blood and tissues from the lining of the uterus -- is expelled. That process, which usually lasts 3 to 7 days, is menstruation. Then the cycle begins again.

Foods That Boost Ovulation

There is a growing body of evidence that links environmental factors to decreases in fertility. If you want to boost your chances of getting pregnant, you may want to eat foods rich in folic acids, buy more organic foods and green products, avoid certain plastics (including plastic wrap), maintain a healthy body weight through diet and exercise, and avoid alcohol and caffeine.

Weight Affects Fertility

A study of women found that those whose body mass index (BMI) was above normal took twice as long to get pregnant as those with a normal BMI. Weight loss for those who are overweight or obese can improve fertility and pregnancy outcomes. According to the American Society for Reproductive Medicine, weight loss of 5%-10% can dramatically improve ovulation and pregnancy rates. Obesity is also a cause of infertility and low testosterone levels in men. Being significantly underweight can also alter hormones of the reproductive organs and be a cause of infertility.

Age Affects Your Conception Chances

Age affects the success rates of a woman's infertility treatments as well as her natural ability to get pregnant. A healthy 30-year-old woman has a 20% chance per month of getting pregnant, while a healthy 40-year-old has a 5% chance. Fertility decreases with age, especially after age 35. Experts say a woman should talk to her doctor if she's under 35 and has been trying to conceive for more than 12 months, or is over 35 and has been trying to conceive for more than 6 months.

Fertility Declines in Older Men, Too

Studies show that sperm count and motility (movement) decrease as men age, as does sexual function. However, unlike women there is no maximum age at which a man can father a child. One study found that it took men age 45 or above longer to achieve a pregnancy once the couple started trying to conceive. If your partner is older, you may want to talk to your doctor about ways to boost your chances of conception.

How Men Can Boost Fertility

Managing stress, avoiding alcohol and tobacco, maintaining a proper weight, and eating a diet high in zinc (found in meat, whole grains, seafood, and eggs), selenium (meat, seafood, mushroom, cereals, and Brazil nuts) and vitamin E may help improve male fertility. So can keeping the testicles cool -- no long hot baths, hot tubs, or saunas, which can decrease the number of sperm.

Treatments for Infertility

A number of factors can cause infertility, so the first step is for your doctor to evaluate you and your partner. Infertility treatments can include taking fertility drugs to stimulate ovulation and in vitro fertilization, which involves removing eggs from the ovaries, fertilizing them (shown at left), and then implanting them back into the uterus.

How Home Pregnancy Tests Work

Home pregnancy tests check your urine for the "pregnancy hormone," called hCG, that your body produces once a fertilized egg implants in your uterus. Usually a home pregnancy test can tell if you're pregnant as early as five days before your first missed period. You can get a false negative if you test too early, so repeat the test a few days or a week later. Your doctor can provide more accurate results with a blood test.

Pregnancy: 5 Early Signs

• You miss a period.
• You need to urinate frequently.
• You tire easily.
• You're nauseous in the morning -- or all day.
• Your breasts become tender and enlarged.

More Reading on Pregnancy

• Pregnancy
• Home Pregnancy Test
• Slideshow: Early Pregnancy Symptoms
• Slideshow: Stages of Pregnancy
• Slideshow: Fetal Development Month by Month