May 25, 2008
Role of Dads’ Sperm in Birth Defects Unknown
SAN JOSE, Calif. -- When Barbora Bell wanted to have kids, she ditched the birth control pills, popped prenatal vitamins, and got more iron and calcium. Her husband's pre-conception regimen was much easier: "He had a glass of wine," Bell said, laughing.
The Los Gatos, Calif., couple didn't hear a single dietary suggestion to help prospective fathers have healthy kids. If they had, Bell said, "we would have been doing it."
Women contribute just half their children's genes. Yet would-be dads are rarely bombarded with pre-pregnancy tips on diet missteps and toxic exposures, even though sperm DNA is vulnerable to defects that can cause possible health problems for their children.
There's a growing push to better understand the male half of reproductive health. New technologies are allowing scientists to delve further into male fertility. Dads' role in birth defects was the focus of a symposium this year at the American Association for the Advancement of Science meeting. And a recent University of California-Berkeley study was the first to link men's diets to sperm DNA errors.
But much of this information never makes it to men.
The relative silence reflects a cultural reluctance to question men's virility and potency, said Cynthia Daniels, a Rutgers University professor who studies the crossroads of science and culture.
"We assume the male reproductive system is like a simple machine," Daniels said. Men's role in fertilization seems so straightforward, it's easy to forget things can go wrong with sperm DNA, she said. And there's an assumption that defective sperm isn't strong enough to get the job done anyway.
But some defective sperm do succeed in fertilizing eggs, potentially causing birth defects or childhood disease. One in 33 California children is born with a birth defect. And scientists still don't know what causes most defects.
Despite the unanswered questions, there's relatively little research on prospective fathers.
"People in the field have had a great deal of difficulty getting funding," said Gladys Friedler, an emeritus professor of Boston University's medical school. Throughout her career from the 1960s to the 1990s, Friedler often was told to abandon studies of male reproduction on the grounds that such research was unnecessary, she said.
A small amount of research has trickled out over the decades. Pesticides were scrutinized after Vietnam War veterans exposed to Agent Orange fathered many children with spina bifida. Older men's sperm was found to have more DNA errors that cause dwarfism. And men who received chemotherapy for testicular cancer temporarily produced defective sperm, which could cause problems if conception occurred too soon after treatment.
In March, UC-Berkeley added to the growing knowledge. In a study utilizing new technology to label sperm DNA, men who ate little folate, a B-vitamin abundant in orange juice and green veggies, had more sperm with the wrong number of chromosomes. That could lead to miscarriages and birth defects like Down syndrome.
The study didn't pinpoint an ideal folate dose, said author Brenda Eskenazi. "But we can still advise that men considering fathering a child should take a multi-vitamin and get enough leafy green vegetables," she said.
Sperm develop over 10 weeks, giving men a defined window before conception to make healthier sperm, said San Jose urologist David Nudell. Women, in contrast, are born with a finite number of eggs. This means men's genes, constantly dividing into new sperm, may be even more vulnerable than women's.
Unlike women who often take vitamins while cutting out caffeine, sushi and pedicures before trying to conceive, "I've never seen a guy come in and say, `I started this three months before we tried,' " Nudell said. "It's how our society is about getting pregnant."
One reason for the uneven information is that most women can regularly ask for advice at their annual ob-gyn visits.
"Most men in their 20s and 30s are probably not seeing doctors at all," Nudell said. "Who are they going to ask?"
But men are beginning to wake up to the problem, said professor Daniels.
"Younger men are quite incensed that these issues have not been addressed," she said. "I'm hopeful that we might have raised a generation of young men willing to open their eyes, look at the evidence, and ask the questions that need to be answered."
Because the science of male fertility is sparse, Nudell gives common-sense advice to the few men who bother asking about pre-conception health: avoid heavy alcohol and drug use, take vitamins and stop smoking _ even though studies of those lifestyle factors have been inconclusive.
And he emphasizes that couples having trouble conceiving should get both partners checked out. "A lot of women get unnecessary treatments," he said. "Men are generally not that proactive about their health."
That's even true for devoted dads who attend every prenatal appointment.
"I didn't talk to my doctor at all," said Los Gatos father Dave Dooley, who fondly remembers his wife's pregnancy ultrasounds. Like most couples, Dave and Melissa Dooley, whose children are now 4 and 2, assumed only mothers needed to consider pre-pregnancy health.
"We're the ones who have to deal with the nine months," said Melissa Dooley.