Nourishing a growing fetus requires additional protein above what is needed to meet the increased metabolic needs of the mother. She needs a minimum of 60 grams of protein per day, more if the mother is a growing teenager. Pregnancy health is dependent upon having a diet high in vitamins, minerals, antioxidants and omega-3 fats, as well as protein. Low fiber, high calorie foods containing hydrogenated oils, refined sweeteners and excessive sodium will fall short of these requirements. Such snacks may also be addictive and are typically consumed at the expense of nutrient-rich foods.
The most obvious effect of eating junk food during pregnancy is excessive maternal weight gain. Paula Bernstein, an obstetrician at Cedars-Sinai, co-author with dietitians Marlene Clark and Netty Levine of "Carrying a Little Extra," writes that overweight and obese women have a significantly higher risk of serious complications such as high blood pressure, pregnancy induced hypertension, gestational diabetes, miscarriage, preterm labor, stillbirth and an increase in birth defects. The Institute of Medicine's guidelines state that in order to minimize risks, mothers who are overweight prior to pregnancy should limit prenatal weight gain to 15 to 25 pounds, and obese women should gain in the range of 11 to 20 pounds. The parameters are based on pre-pregnancy body mass index (BMI), calculated from the height and weight of American women.
A lack of protein in the mother's diet during pregnancy interferes with proper kidney development in the fetus, according to animal studies conducted at Nene University College in Northampton, U.K. Rats fed a protein deficient diet gave birth to offspring that had underdeveloped kidneys, which resulted in the development of high blood pressure and renal disease as the babies reached adulthood. The researchers believe that adult hypertension and coronary heart disease may be "programmed" by intrauterine exposure to poor nutrition.
Neuroscientists at Oregon Health and Sciences University found increased anxiety in the offspring of monkeys who were fed a high fat diet during pregnancy. The researchers also indicated that childhood obesity is associated with an increased risk of depression, poor learning, and attention deficit disorder (ADD). A London study published in the "British Journal of Nutrition" found that pregnant rats fed doughnuts, candy, chips, soda and other junk foods gave birth to offspring that preferred foods high in fat, sugar and salt and were obese at an early age. The researchers found in further studies that the young rats from junk-food eating mothers had more body fat and weaker muscles than rats born to mothers fed rat chow, and showed additional inflammatory changes in their livers.