The study links each 10-fold increase in the blood concentration of four PBDE (polybrominated diphenyl ethers) chemicals to a 30% decrease in the odds of becoming pregnant eachmonth.

These chemicals are used in foam furniture, electronics, fabrics, carpets, plastics and other items. They became common decades ago in the United States when fire safety standards were adopted. They are being phased out nationwide but some are still found in products made before 2004.

The research joins other animal and human studies that show health effects from PBDE exposure and that 97% of U.S. residents have detectable  levels of the chemicals in their blood.

“This latest paper is the first to address the impact on human fertility, and the results are surprisingly strong,” says lead author Kim Harley, associate director of the Center for Children’s Environmental Health Research at the University of California-Berkeley’s School of Public Health.

Harley says the chemicals leach into our environment. She says Californians have particularly high levels of PBDEs, most likely because of the state’s relatively strict flammability laws.

Even though the chemicals are being phased out, Harley remains concerned. “We know even less about the newer flame retardant chemicals that are coming out,” she says in a university press release. “We just don’t have the human studies yet to show that they are safe.”

In the study, published Tuesday in the journal Environmental Health Perspectives, Harley and other researchers measured PBDE levels in blood samples from 223 pregnant women, many of them young Mexican immigrants in an agricultural community. Their analysis takes into consideration exposure to pesticides and other factors that could affect fertility.

The study says it’s not entirely clear how PBDEs  impact fertility.  Animal studies have found that the chemicals can impair neurodevelopment, reduce thyroid hormones and alter levels of sex hormones.

• Sexually transmitted disease, like chlamydia or gonorrhoea
• Infection with the mumps virus after puberty (inflammation of testicles)
• Chronic illness like diabetes, cancer, asthma, thyroid disease or depression
• Undescended testicles
• Testicular tumors, cysts or cancer
• Surgery in your groin or injury to your testicles
• A chromosomal condition, like Klinefelter’s syndrome (when men have an extra X chromosome in most of their cells)

Or if you currently:

• Take medications such as some steroids or antidepressants
• Smoke tobacco or marijuana
• Use a jacuzzi or sauna regularly
• Go on frequent, long-distance bike rides

• Endometriosis
  The uterus is lined with tissue called the endometrium, which normally grows only inside the uterus. However, sometimes it grows outside the uterus, in the reproductive organs or in the intestines, rectum or bladder instead. This condition is called endometriosis. Some women have no symptoms of this happening, while others may experience warning signs. Common symptoms are:

  
  

  • heavy or abnormal menstrual flow
  • very painful menstrual cramps
  • painful sexual intercourse
  • premenstrual spotting
  • painful bowel movements
  • diarrhea, constipation, or other intestinal upsets during menstruation
  • painful or frequent urination during menstruation

• Polycystic Ovary Syndrome
  Many women have polycystic ovaries. But, some women develop polycystic ovary syndrome (PCOS) when their hormonal system gets out of balance, making ovulation rare or irregular. Normally, a woman ovulates when an egg-containing follicle grows and releases a mature egg. Polycystic ovary syndrome makes those follicles stop growing, prematurely. Instead, they gradually build up in the ovaries forming numerous small, benign cysts. Polycystic ovary syndrome affects approximately 4% of women of reproductive age.
  If you have polycystic ovaries you may suffer from:

  
  

  • irregular or nonexistent periods
  • very light or very heavy bleeding during your period
  • acne
  • irregular or infrequent periods within 3 or 4 years after beginning menstruation
  • weightgain, obese
  • excessive hair growth to varying degrees

• Pelvic Inflammatory Disease
  When you’re infected with chlamydia there’s a 25% chance you develop PID. This is when the lining of the uterus and fallopian tubes become inflamed. It can lead to blockages in the fallopian tubes, causing fertility problems. Women with PID can also suffer long-term pelvic pain and are at higher risk of having an ectopic pregnancy (where the fertilised egg implants outside the uterus).
• Fibroids
  Uterine fibroids are tumors in the uterus that grow from muscle tissue. About 25% of women of childbearing age have uterine fibroids (usually 30 to 50 year olds). Fibroids can grow on your uterine wall, within your uterine wall or in the uterine cavity.
• Sexually transmitted disease, like chlamydia or gonorrhoea
  Chlamydia is a sexually transmitted genital infection, it affects both men and women. Chlamydia can be treated with antibiotics but if left undiagnosed and untreated, it can result in fertility problems.
• Irregular or painful periods
• You’ve had pelvic or abdominal surgery before
• Chronic illness like diabetes, cancer, thyroid disease, asthma or depression
• A chromosomal condition, like Turner’s syndrome (when one of the two X chromosomes normally found in females is missing or incomplete)

Or if you currently:

• Take medications, such as some steroids and antidepressants
• Are more than 25% over- or underweight
• Smoke: women who smoke have increased risk conception delay and for primary and secondary infertility, not to mention the risks for your baby if you do get pregnant.

If your periods are very irregular you may not be ovulating at all or infrequently. Again, keep dates and if you are trying for a baby and have no success after 6 months, see your doctor.

However, if you are ovulating then as long as you are having intercourse 2 or 3 times a week, you will be having sex at the right time.

The kits are not foolproof. They can measure LH, but they cannot indicate whether you ovulate after a positive response; LH can surge with or without the release of an egg. False LH surges can also take place before the real one.

For maximum accuracy, follow the kit’s directions to the letter. If you have a 28-day cycle, start the test on day 11 and use it for 6 days. If your cycle is longer, start on day 14 for 9 days. If your cycle runs between 28 and 40 days, ovulation may range between days 14 and 26. The kits generally provide 5 to 9 days’ worth of tests.

Lower abdominal discomfort (mittelschmerz)
About 20% of women feel ovulatory activity, which can range from mild aching to twinges of pain. Some women describe it as one-sided back ache or a specific tenderness. It may last from a few minutes to a few hours. If you notice the same type of pain at about the same time each month, check the condition of your cervical mucus as well. Ovulatory pain is a useful guide for some women.

Change in cervical mucus
As your cycle progresses, your cervical mucus increases in volume and changes texture. The greater volume and changes in texture is due to your body’s rising levels of estrogen. You are considered most fertile when the mucus becomes clear, slippery, and stretchy. Many women compare mucus at this stage to raw egg whites. You are most fertile on the last day you notice cervical mucus of this kind. It usually happens either on the day before, or on the day of ovulation.

A rise in body temperature
When you’ve ovulated, your temperature can increase by 0.5 to 1.6 degrees. You won’t feel the shift but you can detect it by using a basal body temperature (BBT) thermometer. Basal body temperature (BBT) is your temperature when you first wake up in the morning.

You’re most fertile in the 2 or 3 days before your temperature rises. It’s recommended that you chart your temperature for a few months to detect a pattern and discover your likely ovulation date. Then you can plan to have sex during the 2 to 3 days before the day your temperature normally rises. If you do become pregnant, your temperature will stay elevated throughout your pregnancy.

Some women are very aware of when they ovulate, while others don’t notice any changes at all. If you’re thinking about getting pregnant, try to track your cycle for a few months.

In normally fertile couples, there is a 25% chance of getting pregnant each cycle. This means around 80% of women who have sex without using birth control will get pregnant within one year.

Of course, it isn’t always easy to predict when exactly a woman ovulates. It depends in part on the length of your menstrual cycle. You can use the ovulation calendar on our website to find out when you’re ovulating. Or, to remind you at the right time, you can sign up for our ovulation sms service. Then we will send you an sms to let you know when you are most fertile.

Many experts feel that for most couples having sex 2 or 3 times a week is the most effective way of maximising your chances. It’s certainly worth trying for a few months!

It’s estimated that 17% of all couples is infertile; they have difficulties getting pregnant. The ‘problem’ lies with the man as often as with the woman. If you’re one of them, that doesn’t mean you will never have children. About half of those infertile couples have children, but they often need extra time or medical help to get pregnant.

In general, if you have been trying for less than a year, you have no reason to be concerned yet. Read on about what can help in conceiving, and what factors indicate infertility.