Maternal and newborn characteristics are presented in Table 1. The 96 MADRES mothers ranged from age 18.8 to 42.7 years old at delivery, 49.0% of the 96 mothers had a household income less than $30 000, 78 (81.3%) women were Hispanic, 30 (31.3%) women had education level lower than high school diploma, 66 (68.8%) women were overweight or obese before pregnancy, and 61 (63.5%) women had two or more children. 52 (54.2%) newborns were female and 44 (45.8%) were male. The mean ± SD birth weight was 3.36 ± 0.49 kg, and 13 (13.5%) newborns were classified as LGA and 8 (8.3%) newborns were SGA. The mean ± SD gestational age was 39.1 ± 1.4 weeks, 8 (8.3%) were preterm births with gestational age less than 37 weeks, 87 (90.6%) were term births between 37 and 42 weeks of gestation, and only 1 (1.1%) was post-term newborn (after 42 weeks of gestation). Table 1 also presented the associations and p-values between participants’ characteristics and newborn birth weight Z-score. Second-born or later-born newborns had higher birth weight than first-born (p = 0.01) and greater maternal weight gain was associated with higher birth weight in newborn (p = 0.01). No other statistically significant associations were observed between maternal characteristics and newborn birth weight.
Table 1
Characteristics of 96 MADRES mother-newborn pairs and their associations with newborn birth weight Z-scorea. (A) Maternal characteristics
|
Entire sample (N = 96)
|
|
Associations with
Birth Weight Z-score
|
N (%)
|
|
β (95% CI)
|
p-value
|
Maternal age at delivery (year)
|
28.71 (27.58–29.84)b
|
|
-0.03 (-0.08–0.02)
|
0.21
|
Gestational weight gainc (kg)
|
11.90 (10.44–13.36)b
|
|
0.05 (0.01–0.09)
|
0.01
|
Total calorie intake, kcal/d
|
1883 (1766–1999)b
|
|
-0.0002 (-0.0007–0.0003)
|
0.44
|
Hispanic Ethnicity
|
|
|
|
|
No
|
17 (18)
|
|
-
|
-
|
Yes
|
78 (81)
|
|
-
|
-
|
Unknown
|
1 (1)
|
|
-
|
-
|
Household income
|
|
|
|
|
$30,000 or below
|
47 (49)
|
|
REF
|
REF
|
More than $30,000
|
20 (21)
|
|
0.20 (-0.45–0.85)
|
0.55
|
Unknown
|
29 (30)
|
|
0.07 (-0.52–0.66)
|
0.81
|
Maternal education
|
|
|
|
|
Less than 12th grade
|
30 (31)
|
|
REF
|
REF
|
Completed high school
|
33 (34)
|
|
-0.11 (-0.79–0.57)
|
0.74
|
College or technical school or above
|
31 (32)
|
|
0.02 (-0.70–0.74)
|
0.96
|
Unknown
|
2 (2)
|
|
-0.65 (-3.18–1.89)
|
0.61
|
Marital status
|
|
|
|
|
Married
|
27 (28)
|
|
REF
|
REF
|
Living together
|
40 (42)
|
|
-0.32 (-0.95–0.30)
|
0.31
|
Single or divorced
|
23 (24)
|
|
-0.57 (-1.28–0.15)
|
0.12
|
Unknown
|
6 (6)
|
|
-1.02 (-2.89–0.85)
|
0.28
|
Lifetime cigarette smokingd
|
|
|
|
|
Never used
|
64 (67)
|
|
REF
|
REF
|
Ever used
|
32 (33)
|
|
-0.08 (-0.65–0.49)
|
0.79
|
Pre-pregnancy BMI (CDC category)
|
|
|
|
|
Underweight or normal weight
|
30 (31)
|
|
REF
|
REF
|
Overweight
|
31 (32)
|
|
-0.24 (-0.89–0.40)
|
0.46
|
Class 1 obese
|
24 (25)
|
|
0.09 (-0.67–0.86)
|
0.81
|
Class 2 or class 3 obese
|
11 (11)
|
|
0.3 (-0.66–1.26)
|
0.53
|
Parity
|
|
|
|
|
First-born
|
31 (32)
|
|
REF
|
REF
|
Second-born or later
|
61 (64)
|
|
0.80 (0.19–1.41)
|
0.01
|
Unknown
|
4 (4)
|
|
1.51 (-1.13–4.15)
|
0.26
|
Glucose metabolism
|
|
|
|
|
Normal
|
60 (63)
|
|
REF
|
REF
|
Glucose intolerant
|
23 (24)
|
|
-0.06 (-0.68–0.56)
|
0.84
|
GDM or chronic diabetes
|
13 (14)
|
|
0.14 (-0.60–0.88)
|
0.71
|
Hypertension
|
|
|
|
|
Normal blood pressure
|
79 (82)
|
|
REF
|
REF
|
Hypertensive
|
17 (18)
|
|
0.06 (-0.63–0.74)
|
0.87
|
Delivery type
|
|
|
|
|
Normal spontaneous vaginal delivery
|
64 (67)
|
|
-
|
-
|
Non-NSVDe
|
32 (33)
|
|
-
|
-
|
(B) Newborn characteristics |
|
Entire sample (N=96)
|
|
Associations with
Birth Weight Z-score
|
N (%)
|
|
b (95% CI)
|
p-value
|
Birth weight (kg)
|
3.36 (3.26–3.46)b
|
|
-
|
-
|
Gestational age at birth (week)
|
39.13 (38.84–39.42)b
|
|
-
|
-
|
Hispanic Ethnicity
|
|
|
|
|
No
|
14 (15)
|
|
REF
|
REF
|
Yes
|
80 (83)
|
|
0.33 (-0.41–1.07)
|
0.38
|
Unknown
|
2 (2)
|
|
-0.65 (-3.18–1.89)
|
0.61
|
Sex
|
|
|
|
|
Female
|
52 (54)
|
|
-
|
-
|
Male
|
44 (46)
|
|
-
|
-
|
Birth weight categoryf
|
|
|
|
|
AGA (Appropriate for Gestational Age)
|
75 (78)
|
|
-
|
-
|
SGA (Small for Gestational Age)
|
8 (8)
|
|
-
|
-
|
LGA (Large for Gestational Age)
|
13 (14)
|
|
-
|
-
|
a Multivariable linear regression model was used to investigate the association of the main maternal and newborn characteristics with birth weight Z-score.
b These variables are presented as mean (95% confidence interval) rather than N (%).
c Gestational weight gain = The total weight gain during pregnancy period.
d Lifetime cigarette smoking = ever used cigarette before pregnancy and during pregnancy.
e NSVD = Normal spontaneous vaginal delivery; Non-NSVD = planed C-section, unplanned/emergency C-section, vaginal birth after cesarean (VBAC), and vacuum assisted vaginal delivery.
f Small for Gestational age (GA) is defined as < 10th percentile for birth weight; Large for GA is defined as > 90th percentile for birth weight.
Maternal and Newborn Metabolomics in association with birth weight Z-score
MWAS analyses suggested that 808 maternal serum metabolomic features and 737 newborn metabolomic features had statistically significant associations with birth weight Z-score (p < 0.05) (Figure S3). Among maternal serum metabolomic features, 397 (49.1%) and 411 (50.9%) were positively and negatively associated with birth weight Z-score, respectively. Among newborn cord blood metabolomics, 411 (55.8%) and 326 (44.2%) were positively and negatively associated with birth weight Z-score, respectively.
Mummichog pathway enrichment analysis found that the most statistically significant pathways associated with birth weight included dysregulated branched-chain amino acid (BCAA) metabolism, pentose phosphate pathway, butanoate metabolism and fructose and mannose metabolism in mothers at 3rd trimester and dysregulated bile acid biosynthesis, linoleate and omega-3 fatty acid metabolism, and C21-steroid hormone biosynthesis and metabolism in newborns (Fig. 1). Among all identified metabolic pathways that were associated with birth weight, Mummichog analysis provided tentative annotations for 32 maternal metabolomic features and 44 cord blood metabolomic features (Tables S1 and S2). We confirmed three maternal metabolomic features metabolites including fructose, glucose, and 2-deoxyglucose (the top three features in Table S1) and eight cord blood metabolomic features including progesterone, cortexolone, arachidic acid, oxovalerate/ketoisovalerate, ketoleucine/ketoisoleucine, fructose, 2-deoxyglucose, and glucose (the top eight features in Table S2) for their chemical identity by comparing the MS spectra to chemical standards.
Integration of maternal and newborn cord blood metabolomics using xMWAS
To investigate the connection between maternal and newborn metabolomics, xMWAS network analysis was used to dissect 32 maternal and 44 newborn cord blood metabolomic features into 5 subnetworks that were tentatively annotated by Mummichog analysis (Figure S4). Nine maternal metabolites and four newborn metabolites showed stronger connections in the entire network [Degree weight centrality measure (DWCM) > 0.2] (Table S3). The first subnetwork negatively connected a maternal isoleucine biosynthesis related metabolite, (S)-2-aceto-2-hydroxybutanoate, with newborn fatty acids including arachidic acid and octadecenoate. The second subnetwork negatively correlated maternal glucose, fructose, and ketoisovalerate with newborn glucose, fructose, and L-arginine, and it positively correlated maternal glucose, fructose, and ketoisovalerate with newborn carnitines and newborn metabolites involved in branched-chain amino acid metabolism (oxovalerate/ketoisovalerate and ketoleucine/ketoisoleucine). The third subnetwork positively connected a maternal pentose phosphate pathway related metabolite (sedoheptulose 7-phosphate) and a fatty acid oxidation intermediate (tetradecanoyl-CoA) with newborn bile acid metabolism, and newborn C21-steroid hormone biosynthesis and metabolism. The fourth subnetwork positively connected maternal metabolites involved in carbohydrate metabolism (2-deoxyglucose and L-ribulose) with newborn cortexolone, 2-deoxyglucose, and 1-pyrroline-2-carboxylate. Additionally, this subnetwork negatively associated maternal metabolites involved in carbohydrate metabolism with two newborn long-chain acylcarnitines.
Maternal and newborn metabolomics linking maternal parity and gestational weight gain to higher birth weight
As previously presented, among the maternal characteristics, parity and gestational weight gain were the significant risk factors for high birth weight (Table 1). Therefore, LUCID analysis was used to integrate these maternal risk factors with key maternal and newborn metabolomic signatures, as well as to assess the joint association with birth weight.
Among the 76 annotated metabolites associated with birth weight, 9 maternal metabolites and 11 cord blood metabolites had significant associations with parity (all p-values < 0.05) (Table S4). Then, 9 maternal metabolites (N = 1 with confirmed identity) and 11 cord blood metabolites (N = 5 with confirmed identity) were included in the LUCID analysis. 92 mother-newborn pairs with known parous history were assigned to two latent clusters by maternal parity and metabolomic signatures. As shown in Fig. 2 and Table S5, panel a, mother-newborn pairs of latent cluster 2 (N pairs = 32) had significantly higher birth weight Z-score (p < 0.001), and 31 (97%) in this cluster were multiparous. Maternal serum levels of sedoheptulose 7-phosphate and cord blood levels of glucose, fructose, progesterone, and 7alpha,25-dihydroxy-4-cholesten-3-one in the pathway of sugar metabolism were significantly lower in latent cluster 2 than in latent cluster 1, while maternal serum levels of glucose, L-4-hydroxyglutamate semialdehyde, succinate, Cys-Gly, ketoisovalerate, and 1-(1-alkenyl)-sn-glycero-3-phosphate in energy metabolism and amino acid metabolism pathways and cord blood levels of ketoleucine, L-serine, L-4-hydroxyglutamate semialdehyde, and lysophosphatidylcholine in amino acid metabolisms were significantly higher in latent cluster 2 (all p-values < 0.05).
Additionally, gestational weight gain was associated with 1 maternal metabolite and 2 cord blood metabolites with annotation (all p-values < 0.05) (Table S4). These three metabolomic signatures were then included in the LUCID analysis and the 96 mother-newborn pairs were assigned into two clusters (Fig. 2 and Table S5, panel b). Latent cluster 2, which clustered 31 mother-newborn pairs, had significant higher birth weight Z-scores and higher gestational weight gain (both p-values < 0.05). In the LUCID analysis model, maternal (S)-3-hydroxyisobutyrate and cord blood estradiol-17beta in pathways of energy metabolism and C21-steroid synthesis were significantly higher in latent cluster 2 than that in latent cluster1, while latent cluster 2 had significantly lower levels of cord blood N-acetyl-D-galactosamine in comparison with latent cluster 1 (all p-values < 0.05).