What causes infertility? Most people know that a woman’s fertility decreases as she gets older, but even during her most fertile (and otherwise healthy) years, lifestyle choices and external factors can affect a woman’s chances of having a healthy baby. “Women who want to increase their chances of getting pregnant often don’t know the best things to do or what to watch out for,” says Francisco Arredondo, MD, a reproductive endocrinologist and fertility specialist in San Antonio, Texas. Here are some of factors that do (or don’t) affect a woman’s fertility, and what you can do about them if you are trying to conceive.
Carrying around extra pounds can affect hormone production and make it more difficult for a woman to get pregnant, says William Schlaff, MD, chairman of the department of obstetrics and gynecology at Jefferson Medical College, Thomas Jefferson University, Philadelphia. “The more weight a woman gains over her healthy weight, the more she tends to experience decreased ovarian function,” he says. And a 2009 study published in Fertility and Sterility found that women who were obese at age 18 were more likely to develop polycystic ovary syndrome (PCOS) and have problems with infertility. PCOS is the most common hormonal disorder among women of reproductive age, and the leading cause of infertility.
Being too thin
Just as excess body fat can impact fertility, so can not having enough of it. That may be because women who have very low BMIs are deficient in leptin, the hormone that controls hunger and feelings of satiety. Having low leptin contributes to the absence of menstrual periods, according to a 2009 Harvard University study. “Maintaining a healthy body weight—one that falls in the normal BMI range and that is reached through a healthy diet and moderate exercise—is one of the most important things a woman can do to increase her chances of getting pregnant,” says Dr. Arredondo, who recently helped develop Conceivable, (free; iTunes) a new app aimed at helping women increase their chances of getting pregnant.
When a woman reaches menopause, usually in her 40s or 50s, she no longer ovulates and is unable to get pregnant. But even in the decade or so before menopause officially occurs, she may experience fertility problems as her ovulation becomes less regular and her egg count declines—a time known as perimenopause.
There’s no official age when fertility begins to take a dive, but many doctors say that it often becomes increasingly difficult to get pregnant after age 35. This age is different for every woman, though; some may go through perimenopause earlier, while others remain fertile through their 40s. That’s why, says Dr. Schlaff, it’s important for women of any age who are having trouble conceiving to see a specialist sooner rather than later.
Ask your mom how old she was when she went through menopause. If she started on the early side, then you probably will, too. “Women are born with a certain amount of eggs,” says Dr. Arredondo, “and there are certain genetic factors that might make you born with more or less eggs than usual, or that may make you use those eggs faster than other average women.” But you certainly aren’t doomed to relive the same exact scenario your mom did. External factors that don’t necessarily affect you could have impacted your mom.
Exposure to pollutants, pesticides, and industrial compounds can decrease a couple’s ability to have children by up to 29%, according to a 2013 study published in Environmental Health Perspectives. Additionally, a 2015 Washington University study found that 15 common chemicals were associated with early menopause. These chemicals include nine PCBs (which have been banned since 1979 but still exist in older products), three pesticides, two forms of plastics called phthalates (often found in personal care items and beauty products like perfumes and nail polishes), and the toxin furan, a byproduct of industrial combustion.
Smoking can hurt a developing fetus, but lighting up can also drastically affect a woman’s chances of getting pregnant in the first place. Smoking causes up to 13% of all infertility cases, according to the American Society for Reproductive Medicine. (One 2014 study even found that a woman’s smoking may affect the fertility of her sons.)
Cigarette smoke disrupts hormones and damages DNA in both men and women, says Dr. Arredondo. “And it doesn’t have to be heavy smoking, either,” he says. “Even women who smoke moderately or who are exposed to secondhand smoke have disrupted endocrine function and can experience significant fertility issues.”
There’s no evidence that a few drinks a week will affect your fertility, but doctors do caution against heavy drinking—more than one drink a day for women—which has been linked to an increased risk for ovulation disorders. Plus, a 2004 Swedish study that tracked more than 7,000 women for 18 years found that the heaviest drinkers were more likely to have sought out fertility treatment.
You probably already know you should stop drinking if you think you could be pregnant. Drinking during the early stages of pregnancy (and possibly even before conception) has been linked to premature births. As for whether it’s safe to drink later in pregnancy, the jury’s still out. Many doctors say a small amount of alcohol is OK, but the CDC and Surgeon General say it’s best not to indulge since there is no proof that it’s not harmful to the baby.
It’s a myth that you can’t get pregnant while breastfeeding, but at the same time, it’s true that women who are still nursing one child may have trouble conceiving another one. “It impacts ovulation,” says Dr. Schlaff. “It’s not impossible—so it shouldn’t be used as your only birth control method—but it is a decision that can have a negative impact on your fertility.” Older moms who want to have another baby before they have to worry about age-related fertility decline should discuss how long to breastfeed with their doctor. Otherwise, it may be better to wait at least a year and a half before having another child, anyway: a 2014 University of Cincinnati College of Medicine study found that women who wait less than 18 months after having a child to conceive again are more likely to have a shorter pregnancy and preterm birth.
Working out helps keep you slim, strong, and full of energy—all important when you’re trying to get pregnant. Thing is, you can overdo it: “If you’re exercising too much it can have a negative impact on ovulation,” says Dr. Schlaff. It’s not just an issue that affects very thin athletes, either. A 2012 study published in Fertility and Sterility found that normal-weight women who exercised vigorously for more than five hours a week had a harder time getting pregnant.
The most obvious sign of a potential problem is a change in menstrual cycle, says Dr. Schlaff. “It doesn’t have to go away completely, either,” he says. “If you notice that it becomes lighter or shorter, you should talk to your doctor about the implications for your fertility and your health.”
Injectable birth control
Once you stop taking most forms of hormonal birth control, you can get pregnant within a month, says Dr. Schlaff. The one exception: Depo-Provera, the injectable birth control. Each Depo-Provera injection prevents pregnancy for 12 to 14 weeks—and while some women do get pregnant in as little as one month after that protection wears off, it can take other women up to a year to conceive. Doctors recommend women stop using injectable birth control several months before they hope to get pregnant.
A 2015 study published in The Obstetrician & Gynecologist supports the long-suspected theory that thyroid disorders can contribute to ovulation and pregnancy problems, and suggests that women having trouble conceiving be tested for over- or underactive thyroid. “People with significant thyroid disease are typically going to have some pretty obvious symptoms,” says Dr. Schlaff, “but subclinical, undiagnosed hypothyroidism is certainly a recognized problem as well, and we know it can have subtle effects on fertility without a woman knowing it.”
If you’re addicted to venti lattes, some studies suggest you may have trouble getting pregnant. A 2011 study from the Nevada School of Medicine found that caffeine interferes with the muscle contractions that help eggs travel from the ovaries and through the fallopian tubes to the womb, while a 2012 Danish study revealed that drinking five or more cups of coffee a day may cut a woman’s chances of successful in vitro fertilization by half. That said, other studies suggest caffeine plays no role in fertility. Either way, if you’re struggling to conceive, it’s worth taking a look at your caffeine intake and cutting back if you’re drinking more than 200 milligrams a day—that’s1 to 2 8-ounce cups of coffee.
Health issues such as polycystic ovary syndrome, endometriosis, and uterine fibroids can affect a woman’s chances of getting pregnant or successfully carrying a pregnancy to term. Women with autoimmune disorders (such as lupus or rheumatoid arthritis) may also have trouble conceiving, since their bodies may reject a fertilized egg or attack her partner’s sperm. In many cases, though, women with these health conditions can still get pregnant and have healthy babies, says Dr. Arredondo. Working with a medical team to manage and improve symptoms, and seeing fertility help if needed, can increase the chances for success.
Sexual health history
Sexually transmitted infections like chlamydia and gonorrhea can cause pelvic inflammatory disease and cause fertility problems, even years after a woman contracts them. In fact, chlamydia can cause damage to the fallopian tubes without any other symptoms, and many women may not know they had the disease until they experience trouble getting pregnant.
It’s important to note, though, that vaginal infections (like yeast infections) have no effect on fertility, says Dr. Schlaff.
Women with higher levels of an enzyme linked to stress had a harder time getting pregnant in a 2014 study published in Human Reproduction. Researchers say this study doesn’t indicate that stress alone is responsible for fertility problems, but they do suggest that women who have been trying to get pregnant for several months try adopting a stress management program.
“Perceived stress can certainly alter hormone levels and ovulation,” says Dr. Arredondo. “Stress itself is not bad, but when it is in excess—and when we react to it in a negative way—it can have all kinds of impact on our health and our bodies.”