The Michigan Department of Health and Human Services (MDHHS) tracks and reports extensive data related to the rate of birth or the occurrence of births within the state over time. They track data statewide, at the county level, and at the local level. This data allows us to answer questions like: natality (birth rate) measures at the state, county, and place levels. The voluminous data, much of it available to Data Driven Detroit, enables analysts to tackle such questions as:
- Where are the most births occurring? Has this changed over time?
- Do birth rates track numbers of births?
- Are women having children at older ages than in previous years? Are there differences in this by place?
- Does educational attainment affect numbers of births or age of mother?
- Are women getting adequate prenatal care? Are there differences by age, race, or education?
The big question is: What can we learn from all this data that will result in healthier moms and babies?
This post focuses on the first two questions. First, we will look at Michigan overall and then we will zoom in on four areas: Detroit, Wayne County outside of Detroit (OutWayne County), Oakland County, and Macomb County. For each place, we show two sets of graphs, one showing how many babies were born each year (annual number of births) and another showing annual birth rates (the number of births in an age group by the population of women in that group).
Figure 1.
At the state level the numbers of Michigan births usually peak between ages 25 and 34 as they did during these six years. For ages 15-19, 20-24, and 25-29 the annual number of births declined from 2017 to 2022. There was not a marked change in numbers of annual births for women ages 30-40+ during these six years, although there is a hint of an uptick in 2021 and 2022 among women 30-34 and 35-39.
Figure 2.
It’s important to remember that more births might happen in places with more people. To compare birth rates between places more fairly, we recalculate the birth rate by dividing the number of births in an age group by the population of women in that group (the population is an estimation from the American Community Survey). The result of this calculation is the per capita birth rate* which allows us to compare birth rates. For example: 100 births in a population of 1,000 women is a 10% birth rate, this is really different from 100 births in a population of 50,000 women, which is a 0.02% birth rate.
Figure 2 (above) compares the annual age-specific birth rates for the state of Michigan for the years 2017-2019, and 2021-2022**. Generally, birth rates follow the trend in actual birth counts due to the fact that population size doesn’t change much between years. Thus, comparing the numbers of births in Oakland County and Macomb County would likely find many more births in Oakland County simply because Oakland County has a larger population.
To put the comparisons on a common measurement scale, we calculated birth rates (in this case, age-specific birth rates) by dividing the number of births in an age group by the population of women in that group, with the population as estimated by the American Community Survey for a given year. The resulting number allows comparisons based on a common unit of measurement.* What is really interesting here is that there is a greater contrast between the birth rates for teenage women compared to women 40 and older than there is between the numbers of births for the two populations.
Figure 3.
In contrast to births in the state as a whole (Figures 1 and 2), which peaked in the 25-34 ages, the greatest proportion of births to Detroit residents occurred in ages 20-29. In these ages and among 15-19-year-olds, births declined in frequency as they had for the state of Michigan in total and as we will see, for Out-Wayne County, Oakland County, and Macomb County. Similarly, births to women in Detroit ages 30 and older increased or stayed flat during the years 2017-2022.
Figure 4.
Figure 3 showed that there were more births to Detroit residents ages 15-19 than to women 40 and older from 2017-2022. Figure 4, birth rates for Detroit residents, graphically illustrates the extent to which births to teenagers dominate births to women 40 and older.
It is not clear why the trends of birth rates for Detroit women, particularly women 25-29 and 30-34, deviated as much as they did from the trend for numbers of births.
Figure 5.
Out-Wayne County’s profile closely resembled that of Michigan as a whole, with the most births occurring at ages 25-29 and 30-34. Common to both Out-Wayne County and the state of Michigan, births to women younger than 30 declined each year from 2017 to 2022. Ages 30-39 saw an uptick during this time, although the increase was greater for ages 30-34 than for the older age groups.
Figure 6.
Birth rates in Out-Wayne County followed a familiar pattern of decreasing rates from 2017-2022 in ages 15-29 with level or slightly increasing rates at ages greater than 30.
Figure 7.
These trends shift when looking at births in Oakland County. Births to women ages 15-29 in Oakland County decreased during this time period as they did for Michigan as a whole and in Detroit and Out-Wayne County, although it was striking that 30-34-year-olds in Oakland County had far more births than 25-29-year-olds in the county. The Oakland County birth rates reflect these differences.
Figure 8.
Figure 9.
The profile of number of births in Macomb County was similar to the profiles of births in Michigan as a whole and to that of Out-Wayne County, with the majority of births occurring during ages 25-34. In all three of these areas births to women younger than 30 decreased in number over the six years, while births to women 30 and older increased or leveled off. The birth rates for Macomb County (Figure 10) generally track the numbers of births for the county with slight differences for women in their 30s.
Figure 10.
What does this mean?
These charts raise several important issues that may have consequences for the health and well-being of children and mothers.
- Detroit women giving birth during these years were generally younger when they gave birth when compared to the other geographies. Does this make Detroit mothers, especially teen mothers, more likely to have worse outcomes than older Detroit women giving birth?
- These analyses dealt with large, undifferentiated areas (e.g., counties). Counties are big, if we look at data from smaller areas within these bigger regions we might gain more insights.For example, does Pontiac have the same profile as Oakland County? What about Southwest Detroit compared to Detroit as a whole? (One concern with looking at smaller communities is that the number of births might be too small for reliable conclusions)
- Why are there more moms in their 30s having babies in Oakland County than the other geographies? The more typical pattern, except in Detroit, is that births in the 25-29 and 30-34 age ranges are the modal and approximately equal ages for giving birth.
- Do these graphs provide any evidence for an effect of the COVID-19 epidemic on the number or timing of births?
- How do birth trends in Southeast Michigan counties compare to other parts of the state? How do the profiles of these Southeast Michigan counties differ from those of other populous Michigan counties and rural Michigan counties?
Going forward, more blog posts will examine adequacy of prenatal care and Hispanic births. For all of these analyses we will look at the data within these same four geographic areas. We will also analyze the data by characteristics of the mother such as age, educational attainment, race, and ethnicity.
*For more information about the importance of context, see our blog post Context is Key: Making Coronavirus Data More Actionable
**The year 2020 was excluded in the calculation because the population estimates are unreliable due to the pandemic’s impact on data collection.
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