For about 20 percent of couples, there's no obvious reason why it's taking so long to conceive. We've looked beyond the usual suspects: stress, coffee, cigarettes, bad timing, blockages...and birthdays.

By Jena Pincott

You have the universal blood type.

First off: There's no big red flag here. Forty-four percent of us have type O blood, and most have no trouble conceiving. But a study at Yale University School of Medicine got our attention when it found that, among female fertility patients in their 30s, those with type O were twice as likely as other blood types to have a hormone profile that made their ovaries seem older than their age. As a group, their FSH (follicle-stimulating hormone) levels more often passed a threshold (>10 mIU/ml) that suggests a lower egg reserve.

The lesson: "Blood type serves only as an alert -- it's not a risk factor," stresses Lubna Pal, MD, the study's senior author and a researcher in reproductive endocrinology, who doesn't want healthy women to worry needlessly. For those with type O who have been struggling to conceive, she says, the best thing to do with this information is to weigh it with other factors known to reduce fertility. For instance, if you also smoke or your mother reached menopause at an early age, this finding might prompt you to adopt a healthier lifestyle and to talk to your doctor sooner than you might otherwise. Lastly, don't panic: Elevated FSH doesn't prevent you from getting pregnant. (Only levels higher than 20 mIU/ml are considered an indicator of infertility.)

It has been him all along (even if his initial tests came out okay).

For prospective dads, the usual fertility workup (sperm count, volume, concentration, motility and morphology) doesn't reveal the whole picture, says Sheena Lewis, a professor of reproductive medicine at Queen's University Belfast. Problem is, those tests don't detect sperm DNA damage, which Lewis and her colleagues pegged as the major culprit behind "idiopathic infertility" (when doctors have no clue why you're not pregnant yet). In their study, a striking 80 percent of cases with that diagnosis were resolved after testing for sperm DNA damage.

The lesson: Consult with your doctor about a test such as the comet assay, which, Lewis says, measures the amount of DNA damage in individual sperm. (Since this type of testing is still considered experimental, many insurance companies won't cover the cost.) When more than 25 percent of the DNA is abnormal, fertility specialists usually recommend intracytoplasmic sperm injection (ICSI), a procedure that involves selecting sperm and injecting it directly into the egg.

Your "sunshine hormone" levels are low.

The lesson: There's no official vitamin D guideline for fertility (not yet, anyway). But because it can be hard to get enough from the winter sun or from food, the Endocrine Practice Guidelines Committee recommends a moderate 1500–2000 IU daily supplement. (That said, avoid heavy-duty doses: One small study found that they may actually impair fertility.)

Your trusty water bottle is coded No. 3, No. 6 or No. 7….

And you eat the wrong canned tomatoes. Or touch too many cash register receipts. And use the wrong sex toys. Or otherwise have contact with -- and absorb too much of—things that contain the estrogen-mimicking plastic-softening chemical BPA (Bisphenol A). In one investigation that took place at the Massachusetts General Hospital Fertility Center, patients with the highest BPA levels produced 24 percent fewer eggs than average; of those eggs, 27 percent fewer could be fertilized, and fewer embryos implanted. In another study, scientists exposed immature eggs to BPA; the higher the dose, the likelier those eggs were to degenerate or, oddly, act as if they were fertilized even though they weren't. The good news is that our bodies metabolize BPA rapidly, explains study author Russ Hauser, MD, MPH, ScD, a professor at Harvard School of Public Health. "Within 24 hours it can be excreted."

The lesson: We're exposed to many sources of BPA throughout the day -- and levels constantly rise and fall with exposure, Hauser says. Keep your daily load as low as possible and find BPA-free alternatives to those water bottles, cans…and, yes, that pocket rocket.

A common environmental chemical is the culprit.

Unfortunately, other hormone-altering chemicals -- PCBs (polychlorinated biphenyls) and similar pollutants -- linger in the body, says Germaine Louis Buck, PhD, at the National Institute of Child Health and Human Development. She and her colleagues found that a couple's odds of getting pregnant in any given month decreased by about 20 percent when either partner's blood tested for high levels of PCBs and/or their cousin chemicals, which persist in the environment (although PCBs have been banned for decades). Traces of PCBs are nearly everywhere, but a major source is animal fat, where toxins can accumulate. (Beef and fish both contain PCBs, but beef-heavy diets are associated with more abnormal sperm and a 35 percent lower count and concentration. The difference may be that the omega-3 fats in fish are sperm-boosters.)

The lesson: Louis Buck says the best thing to do is to limit exposure by cutting away the fat from meat or fish (how to prepare fish to reduce PCBs) and eat fewer animal products overall. Regardless of diet or exposure, a delay doesn't mean doom: About 80 percent of the couples conceived within a year of trying.

Your gums bleed when you brush.

Do your gums bleed after you brush? Are they red and swollen? Periodontal (gum) disease delays a positive pregnancy test by two months or more, found an Australian study. While women with healthy mouths took an average of five months to conceive, those who had periodontal disease took a little over seven months. Non-Caucasian women who had it took over a year. Swollen gums and deep pockets around the teeth breed bacteria, which enter the bloodstream and trigger inflammation -- potentially reducing an embryo's chances of implantation. To make matters worse, gum disease in men is linked to poor sperm quality.

The lesson: Brush and floss regularly, and get dental check-ups. Keep up the regimen when you're pregnant; that same bacteria-triggered inflammation is associated with miscarriage, low birth rate and premature birth.

He has a very intimate relationship with his technology.

Among some researchers, there’s a concern that electromagnetic radiation (EMR) may scramble a man's sperm, with the cell phone being a primary offender. Several studies found a connection between sperm damage and the habit of carrying a cell phone in a pocket or hip belt, near the reproductive organs. Another study targeted that other indispensable EMR-emitting tool: the WiFi-enabled laptop computer. Compared to non-users, men who used laptops on their laps—for four hours with WiFi on -- had 25 percent immobile sperm (vs. 14 percent), and 9 percent of the survivors had DNA damage (vs. 3 percent). (In case you're wondering, the researchers controlled for laptop heat, which we all know kills sperm.)

The lesson: Research is ongoing, but to be safe, keep laptops and cell phones away from privates.

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