Birth

Birthweight and the length of a pregnancy are recorded for nearly every birth in the country, which makes them the earliest outcomes that can be set against the place where a mother lived. This part asks how early in a life the address shows up. Every chapter compares counties or states and describes groups of births. None describes a particular mother or says why her baby weighed what it did.

Chapter 1.1, Birthweight and preterm birth sets the share of babies born at low birthweight and the share born preterm against county deprivation. Both shares are higher where a county's neighborhoods are more deprived. The chapter then splits the shares by the mother's race and finds that the rate for Black mothers is higher than the rate for white mothers at every level of county deprivation, so the difference between the two groups is not a difference between richer and poorer counties alone. A short section records the fall in the number of births, and studies of income support and insurance coverage during pregnancy are reported under their own research designs.

Chapter 1.2, Infant mortality follows the same births through the first year of life. It compares states and then counties, and among the large counties that publish a death count in every year the infant mortality rate rises with county deprivation. It also compares infants of Black and white mothers and finds the gap in each state that publishes both groups. The files carry no cause of death and no birthweight, so the chapter cannot say how the conditions described in the first chapter relate to the deaths described in the second. It can say that both are more common in more deprived counties.

Chapter 1.3, Where births are falling counts births in the large counties that CDC WONDER identifies. Births fell from 2018 to 2024 in most of them, held level in the South and fell elsewhere, and the losses did not rise in steps with county deprivation. A larger share of births went to mothers in their late thirties and forties. The chapter reports counts and shares and not birth rates, because the staged files hold no counts of women by age. Chapter 1.4, Smoking in pregnancy follows the share of births to mothers who reported smoking, which fell in every income group of large counties. Within a state the share is lower where county income is higher, and whether that slope differs between states depends on how counties are weighted and on the scale of the comparison.