New scientific focus revealing that paternal lifestyle choices can affect health of babies for generations

When my daughter became pregnant with my grandson last year, she stopped drinking. Had she been a smoker, she would have forsworn her Marlboros. Her husband, on the other hand, was free to lift a glass and light up if he so chose. Or was he?

The belief that a pregnant woman is responsible for the well-being of her fetus is easy to understand. A fetus is (literally) connected to its mother. Myriad factors such as a mother’s physical and mental condition, exposure to toxins and whether she is well-nourished have long been recognized as determinants of newborn fitness. Yet the paternal role in producing a healthy baby is rarely considered. That’s unfortunate because emerging science indicates that fathers play a more significant role in pregnancy outcomes than previously thought.

Moreover, both parents need to start thinking about what they eat and how they live their lives well before they decide to conceive.

Traditionally, the father’s role in reproduction focused on the preconception period — whether his sperm was potent enough to fertilize the female egg. These days, thanks to a decadeslong decline in sperm counts, such concerns have moved to the front burner. The evidence that environmental toxins, especially endocrine disrupters (chemicals often found in common items such as personal-care products and plastic containers), may contribute to male infertility is compelling. Lifestyle habits such as smoking and excessive alcohol intake as well as nutrientdeficient diets have also been linked to sperm robustness.

The question is, do low sperm counts or damaged sperm actually have an impact on pregnancy outcomes? The answer is yes. For instance, we know that sperm helps to determine how well the placenta forms — a key factor in fetal development — and that impaired sperm dramatically increases the likelihood of miscarriage, possibly because it is known to contain high levels of free radicals. Moreover, thanks to the science of epigenetics, we are learning that human sperm may carry “biological memories” of abnormalities that can be transferred to offspring. In the case of exposure to certain endocrine disrupters, for instance, rodent studies have shown that the effects are transferred by sperm to more than 90% of male descendants, through three generations.

Here’s how it works. A variety of environmental impacts (stress, toxic exposure and poor nutrition are three key ones) trigger changes not in genes themselves, but in how they are expressed. These changes, known as epigenetic modifications, leave chemical marks on genes that are transferred to future generations through sperm (and egg) cells. This process is known as