Grand Rounds

Medicaid Expansion: Impact on Preterm Birth and Low Birth Weight

BACKGROUND AND PURPOSE:

Both preterm birth and low birth weight are associated with adverse infant outcomes such as
- Increased risk of mortality
- Chronic health conditions
Black women are at higher risk while risks for Hispanic population are similar to non-Hispanic white population
Medicaid expansion under the Affordable Care Act allows states to extend coverage to low-income women regardless of pregnancy status, which may lead to reduced infant mortality
Brown et al. (JAMA, 2019) studied whether Medicaid expansion has impacted rates for low birth weight or preterm outcomes

Observational study (data from 2011-2016)
Participants
- Singleton live births to women
- ages ≥19
Data
- Population-based data from the National Center for Health Statistics Birth Data Files
Group designation by
- State Medicaid expansion status
- Racial/ethnic category
Analysis
- Compare birth outcomes among infants in Medicaid expansion states and non-Medicaid expansion states
- Compare changes in relative disparities among racial/ethnic minorities
Primary outcomes (dependent variables)
- Preterm birth (<37 weeks) and very preterm birth (<32 weeks)
- Low birth weight (<2500 g) and very low birth weight (<1500 g)

15,631,174 births
Racial/ethnic category
- White infants: 8,244,924
- Black infants: 2,201,658
- Hispanic infants: 3,944,665
Features of states with Medicaid expansion
- Higher median incomes | Lower percentage of uninsured females | Higher percentage of minority females | Higher number of primary care physicians | Higher percentage of adults who had their cholesterol checked in the last 5 years | Higher percentage of first trimester prenatal intake
Medicaid-expansion status
- 18 states with expansion: 8,530,751
- 17 states without expansion: 7,100,423
There was no significant change in any of the primary outcomes overall between expansion and non-expansion states

Preterm birth (prexpansion to postexpansion); P = .98
- Expansion state: From 6.80% to 6.67%
- Non-expansion state: From 7.86% to 7.78%
Very preterm birth; P = .37
- Expansion state: From 0.87% to 0.83%
- Non-expansion state: From 1.02% to 1.03%
Low birth weight; P = .20
- Expansion state: From 5.41% to 5.36%
- Non-expansion state: From 6.06% to 6.18%
Very low birth weight; P = .14
- Expansion state: From 0.76% to 0.72%
- Non-expansion state: From 0.88% to 0.90%
However, when data was broken out by race, differences between black infants compared to white infants was reduced in expansion states for all primary outcomes, indicated by a negative difference-in-difference-in-difference coefficient
- Preterm birth (10.21% to 9.61%): −0.43 percentage points [95% CI, −0.84 to −0.02], P = .05
- Very preterm birth (1.97% to 1.81%): −0.14 percentage points [95% CI, −0.26 to −0.02], P = .03
- Low birth weight (9.96% to 9.50%): −0.53 percentage points [95% CI, −0.96 to −0.10], P = .02
- Very low birth weight (1,82% to 1.69%): −0.13 percentage points [95% CI, −0.25 to −0.01], P = .04
This benefit in Medicaid expansion was not seen for Hispanic infants

There was no statistical difference overall between states that did and did not expand Medicaid
However, when refining the analysis based on race, there was a significant decrease in disparities in preterm birth or low birth weight for black infants
The authors state

The findings here suggest that earlier and continual access to insurance coverage may provide an important opportunity for improving infant outcomes.

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