The key indicators monitored by PNSS are:
Demographic Variables —The major demographic variables influencing pregnancy outcome are ethnicity, maternal age, marital status and socioeconomic status .
- Pre-pregnancy Weight Status is determined by the body mass index (BMI). Reference criteria for normal, underweight and overweight are based on the Institute of Medicine, National Academy of Sciences report on Nutrition During Pregnancy.
- Weight Gain During Pregnancy —Current recommendations for prenatal weight gain are 25–35 pounds for women entering pregnancy with normal weight/height status. Adjustments are made for underweight or overweight women, as recommended by the National Institute of Medicine. Weight gain is classified as ideal, less than ideal and greater than ideal.
- Low Hemoglobin and/or Hematocrit is used as crude indicators of anemia and poor iron status. The hemoglobin and hematocrit cut-offs for childbearing-aged women have been developed by CDC. Prevalences are summarized for prenatal and postpartum women.
- Smoking doubles the risk of low birth weight and is a contributing factor in 20–40 percent of low birth weight infants born in the United States. A woman who stops smoking when she first discovers that she is pregnant reduces her risk of poor pregnancy outcome.
- Alcohol consumption is associated with adverse outcomes during all stages of fetal development. Alcohol intake during the first trimester is associated with fetal malformation, the second with fetal loss, and the third with low birth weight.
- Medical Care —The quality, quantity and timing of prenatal care influence pregnancy outcome. The risk of low birth weight is reduced for women who initiate care during the first trimester of pregnancy.
- Entry into WIC—percentages are reported by stage of pregnancy and postpartum.
- Birth Weight: low birth weight (<2,500 grams of 5.5 pounds); normal birth weight (2,500–3,999 grams); high birth weight (4,000–5,999 grams).
- Gestational Age < 37 weeks
Infant Feeding Practices —include prevalence for children who were ever breastfed , and those receiving breast milk only, formula only or both breast milk and formula.