In 2014, when 800-meter runner Alysia Montano was 34 weeks pregnant, she ran that distance in 2 minutes 32.13 seconds — 35 seconds slower than her personal best.

This year, when their sponsor, Nike, suspended the pay of female athletes for taking pregnancy leave, Montano and others went public with just how tough it was to balance their careers with wanting to be a mom. (Nike has since revised its policies.)

A new study shows that women can find it equally challenging to get the right balance of nutrients while pregnant. That increases the risk of premature birth, as well as birth defects and developmental problems, and even cancer, in their offspring.

Recent research found that around 70% of pregnant American women ages 20 to 40 don't get the average requirement of vitamins and minerals.

Especially lacking (even in women who take a supplement) are vitamins D, C, A, B6, K and E, as well as the minerals choline, iron, folate, calcium, potassium, magnesium, and zinc.

On the other hand, many pregnant women get too much sodium; 40% exceed the upper limit for iron; and 33% are over the top on folic acid.

The solution? Have your doctor check your nutrient levels and consider consulting a nutritionist.

Eat seven to nine servings of veggies, fruit, and 100% whole grains daily, and stick to lean meat-based proteins (no red meat).

In addition, take a prenatal multivitamin and omega-3 DHA as soon as you start thinking about getting pregnant. And check nutrition labels for added folic acid, so you won't exceed your upper limit.