differing first year mortality rates of term births to us-born and foreign- born mothers james w....

Differing First Year Mortality Rates of Term Births to US-born and Foreign-

born Mothers

James W. Collins, Jr.

11/7/15

Transgenerational Factors

Factors, conditions, and environments experienced by one generation that relate to

the pregnancy outcome of the next generation

Differing Birth Weight in Illinois (David and Collins, NEJM, 1997)

0

2

4

6

8

10

12

14

US-born Blacks African-born Blacks US-born Whites

% L

BW

(<

250

0g)

012345

6789

10

US-born Blacks African-born Blacks US-born Whites

% L

BW

(<

250

0g)

Differing LBW Rates Among Low-risk Women in Illinois

(David and Collins, NEJM, 1997)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

US-born Blacks African-born Blacks US-born Whites

% V

LB

W (

< 1

500g

)Differing VLBW Rates Among Low-risk

Women in Illinois (David and Collins, NEJM, 1997)

Maternal Race and Infant Birth Weight Among Low-Risk Women in Illinois

(Pallotto et al, AJE, 2000)

012345

6789

10

US-born Blacks Caribbean-born US-born Whites

% L

BW

(<

250

0g)

Low Birth Rates by Maternal Age among Foreign-born Black Mothers

(Deal et al, Ethn Dis, 2014)

VLBW RATES OF MEXICAN-AMERICANS BY MATERNAL GENERATIONAL RESIDENCE IN

THE U.S.Collins and David, Ethn Dis, 2004)

00.20.40.60.8

11.21.41.61.8

2

Mexican-Born (N=39,050) First Generation US-Born(N=2,203)

Infa

nt V

LB

W R

ates

(pe

r 10

0)

Genetic Code vs. Zip Code?Two Leading Theories: • “Genetic Code Theory”:

– AA and MA women migrants to the US are intrinsically healthier and have better birth outcomes than those who do not migrate (Wingate, SSM, 2006; Ray et al, CMAJ, 2007).

• “Zip Code Theory”: – Lifelong residence in the US, or something closely related to it,

is detrimental to the birth outcome of AA and MA women (David and

Collins, AJPH, 2007; Collins and David, Clinics Perinat, 2009; Parker-Dominguez, SSM, 2010)

Testing the Genetic Theory

• Wingate et al, MCHJ 2009:– US-born Blacks who moved out of state had better birth outcomes

compared to those who did not move, even after risk factors were controlled.

– Data support the healthy migrant theory. – Limitation: No adjustment for neighborhood income.

Study Objective• To determine the association between migration

from Chicago to the suburbs and preterm birth (<37 wks, PTB) rates among African Americans and Whites.

Natural Experiment: White Flight from Chicago

ChicagoSuburban CookCollar Counties

http://upload.wikimedia.org/wikipedia/commons/1/15/Illinois-counties-map.gif

White Mothers

N= 45, 135African-American Mothers

N=41, 221

88%

10% 2%

ChicagoSuburban CookCollar Counties

30%

41%

29% ChicagoSuburban CookCollar Counties

White mothers were more likely to migrate Collins et al, MCHJ, 2013

P<0.0001, chi square test

PTB rates improved with migration for both races Collins et al, MCHJ, 2013

White Mothers African American Mothers0

2

4

6

8

10

12

14

5.1

13.5

4.2

9.9

3.5

10.7

Chicago

Suburban Cook

Collar Counties

PT

B r

ates

/10

0 bi

rths

p<0.05

White mothers who migrated had less risk factors.

White Mothers: Distribution of Risk Factors

Chicago Cook Collar

Maternal Age <20 8% 2% 2%

Education <12 yrs 19% 5% 5%

Unmarried 25% 8% 7%

Smoker 24% 18% 16%

Inadequate Prenatal Care 14% 6% 6%

Neighborhood Income in Lowest Quartile

21% <1% <1%

AA mothers who migrated had less risk factors factors.

African-American Mothers: Distribution of Risk Factors

Chicago Cook Collar

Maternal Age <20 27% 16% 19%

Education <12 yrs 36% 15% 22%

Unmarried 83% 55% 58%

Smoker 20% 15% 18%

Inadequate Prenatal Care 33% 21% 32%

Neighborhood Income in Lowest Quartile

74% 16% 4%

Migration benefits were explained by known risk factors Collins et al, MCHJ, 2013

Adjusted OR (95% CI)

Chicago-Chicago Reference

Chicago-Cook OR= 0.9(0.8, 1.1)

Chicago-Collar OR= 0.9(0.8, 1.1)

Adjusted OR (95% CI)

Chicago-Chicago Reference

Chicago-Cook OR= 0.9(0.8, 1.2)

Chicago-Collar OR= 1.0(0.9, 1.3)

Whites African-Americans

Implications• Our findings do not support the healthy migrant

theory as a valid explanation for the discrepancy in birth outcomes between foreign- and US-born AA and MA women.

Change in Mean Birth Weight Across a Generation

(Collins et al, AJE, 2002)

65

45

17

-57-80

-60

-40

-20

0

20

40

60

80

US-born White European-bornWhite

US-born AA

Cha

nge

in b

irth

wei

ght (

g)

African/Carib-AA

Change in Mean Birth Weight Among infants of Married Women Across a

Generation (Collins et al, AJE, 2002)

69

3551

-95-120

-100

-80

-60

-40

-20

0

20

40

60

80

US-born White European-bornWhite

US-born AA

Cha

nge

in b

irth

wei

ght

(g)

African/Carib-AA

MLBW Rates Across a Generation (Collins et al, AJE, 2002)

02

46

810

1214

US-BornWhites

Foreign-Born

Whites

US-bornAA

African-Carib-

Born AA

Women's Race and Nativity

ML

BW

rat

es (

per

100)

DaughtersGrand-daughters

MLBW Rates Among Infants of Married Women Across a Generation (Collins et al, AJE, 2002)

02468

10121416

US-BornWhites

Foreign-Born

Whites

US-bornAA

African-Carib-AA

Women's Race and Nativity

ML

BW

rat

es (

per

100)

DaughtersGrand-daughters

Study Objective

To explore the birth weights of the direct female descendants of US-Born and Mexican-Born Mexican-American Women.

Change in Mean Birth Weight Across a Generation

65

45

11

-28-40

-20

0

20

40

60

80

US-born White European-bornWhite

US-born MA

Cha

nge

in b

irth

wei

ght (

g)

Mexican-born MA

Change in Mean Birth Weight Between Gen 2 and Gen 3 among the Female Descendants

of Gen 1 Mexican-Born Women

-120

-100

-80

-60

-40

-20

0

20

Cha

nge

in b

irth

wei

ght

(g)

marriedunmarried< 20yrsOverall

20-35yrs

-28 (-63, 7)

-108 (-166, 50)

6 (-14, 26)

-67 (-118, 16)

-16 (-39, 10)

Term Infants

Study Objectives• To determine whether maternal birth in the US

is a risk factor for first year mortality among term (37-42 wks) births to non-Latino White, AA, and MA mothers.

• To ascertain the degree to which known individual level risk factors modify the relationship between maternal nativity and IMR among White, AA, and MA term births.

Methods• 2003-2004 National Center for Health Statistics linked

live birth-infant death cohort files of term (37-42 wks) births to non-Latino White, AA, and MA mothers.

• Infant variables: birth weight, first year mortality.• Maternal variables: nativity, age, education, parity,

marital status, adequacy of prenatal care utilization (Kotelchuck Index).

• Stratified and multivariable binomial regression analyses were performed.

Term IMR by Maternal Nativity and Race/Ethnicity(Collins et al, MCHJ, 2013)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

White* African-American* Mexican-American*

US born

Foreign born

n=22

6,62

1

n=78

2,45

2

n=38

8,3

37

n=71

0,8

37

n=3,

684,

569

n=11

8,24

6# de

aths

/1,0

00 li

ve b

irth

s

Leading Cause-Specific Term IMR (per 1,000) by Maternal Race/Ethnicity and Nativity (Whites)

(Collins et al, MCHJ, 2013)

Leading Cause of Death

WhiteUS-born

WhiteForeign-born RR (CI 95%)

CongenitalAnomalies 0.6 0.5 1.3 (1.1-1.5)

SIDS 0.5 0.1 4.7 (3.2-7.1)

Injuries 0.2 0.1 2.2 (1.5-3.3)

Leading Cause-Specific Term IMR (per 1,000) by Maternal Race/Ethnicity and Nativity (AA)

(Collins et al, MCHJ, 2013)

Leading Cause of Death

AAUS-born

AAForeign-born RR (CI 95%)

CongenitalAnomalies 0.9 0.9 1.0 (0.9-1.3)

SIDS 1.0 0.2 4.9 (3.3-7.3)

Injuries 0.5 0.1 4.1 (2.4-7.1)

Leading Cause-specific Term IMR by Maternal Race/Ethnicity and Nativity (MA)

Leading Cause of Death

MAUS-born

MAMexican-born

RR (CI 95%)

CongenitalAnomalies

0.7 0.9 0.8 (0.7—0.9)

SIDS 0.4 0.1 3.0 (2.3-3.8)

Injuries 0.2 0.1 2.2 (1.6-3.0)

Distribution of Selected High-Risk Individual Level Risk Factors by Maternal Nativity (Whites)

US-Born WhiteN=3,684,569

Foreign-Born WhiteN=226,621

LBW (<2500g) 2.5% 2.3%

Maternal Age <20y 7.5% 2.5%

Maternal Education <12y 11.0% 7.7%

Parity 3+ 8.5% 9.0%

Unmarried 23.9% 10.6%

Term IMR by Maternal Age and Nativity(Whites)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

<20* 20-29* 30-39* 40+*

US-born

Foreign-born

# de

aths

/1,0

00 li

ve b

irth

s

Maternal Age (years)

Term IMR by Maternal Education and Nativity(Whites)

0

1

2

3

4

5

6

<12* 12* >12*

US born

Foreign born

# de

aths

/1,0

00 li

ve b

irth

s

Maternal Education (years)

Term IMR by Marital Status and Nativity(Whites)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

Unmarried* Married*

US Born

Foreign Born

Marital Status * Signfies statistical significance

# de

aths

/1,0

00 li

ve b

irth

s

Distribution of Selected High-Risk Individual Level Risk Factors by Maternal Nativity (AA)

US-Born AAN=782,452

Foreign-Born AAN=118,246

LBW (<2500g) 5.7% 3.6%

Maternal Age <20y 17.5% 4.2%

Maternal Education <12y 24.3% 14.8%

Parity 3+ 14.5% 13%

Unmarried 72.5% 38.9%

Term IMR by Birth Weight and Nativity(AA)

0

2

4

6

8

10

12

14

16

18

LBW non-LBW*

US Born

Foreign Born

Marital Status * Signfies statistical significance

# de

aths

/1,0

00 li

ve b

irth

s

Term IMR by Maternal Age and Nativity(AA)

0

1

2

3

4

5

6

<20* 20-29* 30-39* 40+*

US-born

Foreign-born

# de

aths

/1,0

00 li

ve b

irth

s

Maternal Age (years)

Term IMR by Maternal Education and Nativity(African-Americans)

0

1

2

3

4

5

6

<12* 12* >12*

US born

Foreign born

# de

aths

/1,0

00 li

ve b

irth

s

Maternal Education (years) * Signfies statistical significance

Term IMR by Marital Status and Nativity(AA)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

Unmarried* Married*

US Born

Foreign Born

Marital Status * Signfies statistical significance

# de

aths

/1,0

00 li

ve b

irth

s

Distribution of Selected High-Risk Individual Level Risk Factors by Maternal Nativity(MA)

US-Born MAN=388,337

Foreign-Born MAN=710,837

LBW (<2500g) 2.5% 2.3%

Maternal Age <20y 12.5% 6.5%

Maternal Education <12y 31.4% 65.5%

Parity 3+ 12.3% 15.6%

Unmarried 48.2% 41.2%

Term IMR by Maternal Age and Nativity(MA)

0

0.5

1

1.5

2

2.5

3

<20* 20-29* 30-39* 40+*

US-born

Foreign-born

# de

aths

/1,0

00 li

ve b

irth

s

Maternal Age (years)

Term IMR by Maternal Education and Nativity(Mexican-Americans)

0

0.5

1

1.5

2

2.5

3

3.5

<12* 12* >12*

US Born

Foreign Born

Maternal Education (years) * Signfies statistical significance

# de

aths

/1,0

00 li

ve b

irth

s

Term IMR by Marital Status and Nativity(MA)

0

0.5

1

1.5

2

2.5

3

Unmarried* Married*

US Born

Foreign Born

Marital Status * Signfies statistical significance

# de

aths

/1,0

00 li

ve b

irth

s

Multivariable Binomial Regression Analyses (Collins et al, MCHJ, 2013)

• The adjusted (controlling for maternal age, education, parity, adequacy of prenatal care and region of birth) RR of infant mortality for non-LBW term births of US-born (compared to Foreign-born) White, AA, and MA mothers were 1.5 (1.3-1.7), 1.7 (1.5-2.1), and 1.6 (1.4-1.8), respectively.

• The adjusted OR of SIDS among US-born (compared to Foreign-born) White, AA, and MA mothers were 3.1 (2.0-4.7), 2.8 (1.8-4.2), and 2.9 (2.2-3.9), respectively.

Limitations

• Vital records do not include duration of US residence for foreign-born mothers.

• No information on neighborhood level factors.

• No information of adequacy of the utilization of pediatric care.

Conclusions• Term births to US-born White mothers have a

1.7-fold greater IMR than their peers with foreign-born mothers independent of the known individual level risk factors.

• The disparity is not limited to a singular cause of death and is widest among deaths due to SIDS.

• A similar phenomenon occurs among African-Americans and Mexican-Americans.

Conclusions

• US-born mothers have approximately a 3-fold greater SIDS rate than their peers with foreign-born mothers.

• More detailed studies are needed to determine the extent to which term infant sleep positioning modifies the association of maternal nativity and SIDS.

Implications

• The fact that the same phenomenon occurs among the three leading racial/ethnic groups in the US pinpoints the problem to the presence of risk factors among US-born women (i.e. lifelong residence in the US) rather than to the presence of protective factors among foreign-born women (i.e. healthy immigrant hypothesis).

Implications• Our findings do not support the healthy migrant

theory as a valid explanation for the discrepancy in birth outcomes between foreign- and US-born African-American women.

Speculation

• Unmeasured household factors underlie the maternal nativity disparity in term infant outcome regardless of race or ethnicity.

• Possibilities include maternal nativity differences in daycare practices and/or the presence of extended family members residing in the home.

Term IMR by Maternal Nativity and Race/Ethnicity(Collins et al, MCHJ, 2013)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

White* African-American* Mexican-American*

US born

Foreign born

n=22

6,62

1

n=78

2,45

2

n=38

8,3

37

n=71

0,8

37

n=3,

684,

569

n=11

8,24

6# de

aths

/1,0

00 li

ve b

irth

s

Study Objective

• To determine the extent to which maternal demographic risk factors explain the racial disparity in IMR among term infants.

Leading Cause-Specific IMR (< 365d) by Race

0

2

4

6

8

10

12

Congenital Anomalies

SIDS Birth Asphyxia

White

African-American

dea

ths/

1,00

0 liv

e-bi

rths

Cause Specific Neonatal Mortality Rate (NMR, <28d) by Race

0

1

2

3

4

5

6

7

Congenital Anomalies SIDS Birth Asphyxia

White

African-American

dea

ths/

1,00

0 liv

e-bi

rths

Cause Specific Post-neonatal Mortality Rates (PNMR, 28-365d) by Race

0

2

4

6

8

10

12

SIDS Congenital Anomalies

Accidents

White

African-American

dea

ths/

1,00

0 liv

e-bi

rths

Distribution of Selected Risk Factors

0

10

20

30

40

50

60

70

80

LBW* Age <20y* Education <12y*

Unmarried* 3+ prev births*

Inadequate PNC*

Whites

African-Americans

%

Term IMR among Low-Risk* White and African-American Mothers

0

0.5

1

1.5

2

2.5

3

White African-American Category 3

dea

ths/

1,00

0 liv

e-bi

rths

*married, college-educated mothers who received adequate prenatal care adequate prenatal care

Multivariable Binomial Regression Models

The raw and adjusted RR for infant death (365d) for AA (compared to Whites) were 1.7 (1.7-1.8) and 1.1 (1.1-1.2), respectively

The raw and adjusted RR for neonatal death (<28d) for AA (compared to Whites) were 1.3 (1.2-1.4) and 1.0 (1.0-1.1), respectively

The raw and adjusted RR for post-neonatal deaths (28-365d) for AA (compared to Whites) were 2.0 (1.9-2.1) and 1.1 (1.1-1.2), respectively