I’m 36 and can't get pregnant. Am I too old?

Welcome to the updated Health section of Today.MSNBC.com, the "Today" show’s Web site! I’m Judith Reichman, M.D., the program’s medical contributor on women's health. I hope to address your questions and concerns in my weekly column, so please e-mail me. Meanwhile, you will find many answers to your questions in my latest book, "Slow Your Clock Down: The Complete Guide to a Healthy, Younger You," published this month by William Morrow, a division of HarperCollins.

Q: I’m 36 and have been trying to get pregnant for six months. Should I worry?

A: Not yet. But you might have to soon.

It’s unfair, but as we get older, our eggs develop quality-control issues. It gets harder — and takes longer — to get pregnant.

For women between 19 and 26, there’s a 50 percent chance of achieving pregnancy in one menstrual cycle, assuming they have intercourse at the time of ovulation.

For women in their late 30s, this falls to 30 percent. In other words, there’s a 70 percent chance each month that you won’t conceive.

Equally unfair, miscarriage rates rise with age. For 35-year-olds, the rate of pregnancies ending in live births is half that for women in their 20s. By age 45, it is down 95 percent.

Each egg and sperm cell contains half the chromosomes needed to make a complete embryo. These chromosomes are time-vulnerable. When asked to do their share in creating the embryo, they no longer do so satisfactorily. They break, collapse or go to the wrong place.

It’s those chromosomal abnormalities that cause most miscarriages — it’s natures way of stopping the development of a malformed fetus.

But you needn’t feel totally fertility-challenged. There are things you can do to make the most of every cycle:

Time intercourse properly
An egg is ready for fertilization during ovulation, or 14 days before your period. If your cycle is short, you may ovulate even if you are still bleeding. You should be having intercourse during ovulation.

Start early, not late
Because sperm can live for a week inside your cervix waiting to fertilize an egg, start trying to conceive before you ovulate. You can start trying on day 10, repeating every day or two. Once released, an egg can be fertilized for only 24 hours, so you won’t get pregnant if you have intercourse a day after ovulation.

See your gynecologist if your cycle is shorter than 21 or longer than 35 days. You may not be ovulating.

Take your temperature
If you’re not sure when you ovulate, you can figure it out by taking your basal body temperature (BBT) each morning with a special thermometer, available in drugstores. (Your BBT is the temperature of your body at rest.) When you ovulate, your body temperature rises almost half a degree. Alternatively, you can use an ovulation kit or mini-computer that tests for a pituitary hormone that rises during ovulation.

Semen analysis
At least 40 percent of couples experience infertility resulting from sperm problems alone.

A blood test for FSH
This can determine whether you have elevated levels of follicular stimulating hormone (FSH). High levels sometimes indicate early menopause.

A blood test for thyroid
If abnormal, this can prevent ovulation.

An infections test
A cervical culture can test for infections or sexually-transmitted diseases. Such conditions can interfere with fertility.

A special X-ray (HSG)
During this procedure, called a hysterosalpingogram (HSG), dye is injected through the cervix to see whether there are tumors or scar tissue impeding pregnancy.

If these tests appear normal, you can consult with a reproductive endocrinologist, who can offer medications to enhance ovulation, or even more advanced techniques, like in-vitro fertilization. At least one out of 150 babies now born in the western world is made with high-tech help.

Dr. Reichman’s Bottom Line: Before you fret, make sure you get the basics right, by timing intercourse properly. A lot of women have problems getting pregnant, but modern science is able to help many of them.

Dr. Judith Reichman, a regular “Today” show contributor, has practiced obstetrics and gynecology for more than 20 years. Her latest book, "Slow Your Clock Down: The Complete Guide to a Healthy, Younger You," is published this month by William Morrow, a division of HarperCollins.

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