3 Results
There were 8,147 participants that met inclusion criteria(Fig.
1 ). Participants’ demographic and obstetric characteristics are shown
in Table 1 . Maternal GRSBW values ranged from
-0.214 to 0.713 and were positively associated with infant BW (p
0.06, meaning that a change in GRSBW of 1.0 (essentially
the entire range of possible GRSBW values) is associated
with a 6% increase in BW. The measures of association for terms in the
initial model are shown in Table 2 .
Among the included nuMoM2b participants, the largest self-identified
racial group was White, (n=5394, 64.1%), followed by Black/African
American (n= 1139, 14.0%), unknown (n=699, 8.6%), multiracial (n=508,
6.2%), and Asian (n=358, 4.4%). Genetically predicted continental
ancestry groups, in order of decreasing size, were EUR (n=5,099,
62.6%), AFR (n=1,383, 17.0%), AMR (n=1028, 12.6%), EAS (n=274,
3.4%), UNK (n=264, 3.2%), and SAS (n=99, 1.2%). Within each
self-identified racial group, the most common genetic ancestry was as
follows: White: EUR (91.6%); Black/African American: AFR (98.8%);
Unknown/not reported: AMR (69.4%); multiracial: AFR (30.1%); Asian:
EAS (66.5%); Native Hawaiian/Pacific Islander: EAS (68.8%); American
Indian/Alaska Native: AMR (76.5%). Overlap between race and predicted
ancestry is reported in Table 3 .
Figure 2 shows the results of our primary analysis our
assessing the generalizability of the association between
GRSBW and infant BW by self-identified race. The
association between GRSBW and infant BW was only
significant among participants who self-identified as White (ꞵ=0.036,
95% CI 0.01-0.062) or more than one race (ꞵ=0.096, 95% CI
0.008-0.184).
Across racial groups, the magnitude of the association between
GRSBW and infant weight varied widely; the magnitudes of
the association in Asian and multi-racial groups (0.09 and 0.1,
respectively) were more than double that of White and Black groups (0.04
for both). The variation in the magnitude of the association and
statistical association across racial groups is shown in Figure
2.
Figure 3 demonstrates the results for analyses assessing the association
between GRSBW and infant weight within genetically
predicted ancestry groups rather than self-identified race.
GRSBW was associated with BW in the EUR (ꞵ=0.044, 95%
CI 0.017-0.07, p=0.007) and AMR (ꞵ=0.073, 95% CI 0.012-0.135, p=0.007)
ancestry groups but not AFR, EAS, SAS, or unknown groups (Figure
3 ).
Two final log-linear models each assessed the association between
self-identified race or genetically predicted ancestry and BW after
controlling for GRSBW in the entire included cohort,
using the largest groups in each category (White race, EUR predicted
ancestry) as the referent groups. For all groups except American
Indian/Alaska Native, self-identified race was independently associated
with lower BW after controlling for GRSBW, gestational
age, and infant sex (Table 4 ). All genetically predicted
ancestry groups except for UNK remained independently associated with
lower BW (Table 4 ). Coefficients and confidence intervals for
all included terms in each of the models in Table 4 are shown inSupplementary Tables 1 and 2 .