Trends in low and very low birthweight infants
The percentage of infants who had low birthweight (weighing less than 2,500 grams, or 5.5 pounds) declined slightly from 1970 to 1980, from 8 to 7 percent of all births. The percentage then increased slowly but steadily to a peak in 2006, when it was again at 8 percent. Since then, the percentage has remained relatively steady. As of 2016, the percentage of infants with low birthweight remained at 8 percent (Appendix 1).
The percentage of infants with very low birthweight (weighing less than 1,500 grams, or 3.3 pounds) has increased slightly since 1980,1 but has stayed fairly consistent since the 1990s. One percent of infants born in 2016 had very low birthweight (Appendix 1).
Research indicates that the overall increase in low birthweight rates is partly the result of an increase in multiple births after 1980, although the rate among singleton births increased as well. In addition, improvements in technologies used to monitor at-risk pregnancies may have contributed to an increase in cesarean section deliveries and the number of low-weight births.2