Impact of Pre-Pregnancy Hemoglobin Level on the Association Between Pre-Pregnancy Body Mass Index and Gestational Diabetes Mellitus: A Retrospective Cohort Study in a Single Center in China

Figures & data

Table 1 Participants’ Characteristics of the Total Sample Population and Subgroups Stratified by Body Mass Index

	Total	BMI<18.5	18.5≤BMI≤24.9	25.0≤BMI≤29.9	BMI≥30
	n=1289	n=180	n=944	n=137	n=28
Age (years)**	29.6±4.0	28.1±3.6	29.8±3.9	30.2±4.4	29.8±4.2
Pre-pregnancy BMI (kg/m^2)**	21.5±3.1	17.6±0.8	21.3±1.7	26.6±1.2	31.5±3.3
Pre-pregnancy systolic blood pressure(mmHg)**	112.0±11.1	109.9±12.2	111.4±10.6	116.6±11.2	121.1±11.8
Pre-pregnancy diastolic blood pressure(mmHg)**	70.0±8.8	69.5±9.0	69.7±8.5	71.5±10.4	76.4±8.8
Smoking exposure**	99(7.6)	10(5.6)	61(6.5)	20(14.6)	8(28.6)
Family history of diabetes**	305(23.7)	37(20.6)	212(22.5)	44(32.1)	12(42.9)
Alcohol consumption*	97(7.5)	14(7.7)	64(6.8)	14(10.2)	5(17.9)
Pre-pregnancy Hb levels (g/L)**	123.3±9.3	120.3±8.8	123.4±9.2	126.2±9.2	128±11.4
OGTT for GDM screening
FPG (mmol/L)**	4.5±0.5	4.3±0.3	4.4±0.4	4.9±0.9	4.8±0.7
1hPG (mmol/L)**	7.2±1.7	6.8±1.5	7.1±1.6	8.1±2.2	8.0±1.8
2hPG (mmol/L)**	6.4±1.4	6±1.2	6.4±1.3	7.1±1.8	6.7±1.6
HbA1c at GDM screening(%) **	4.7±0.5	4.5±0.4	4.6±0.5	4.9±0.6	5.2±0.4
GDM**	187(14.5)	11(6.1)	120(12.7)	47(34.3)	9(32.1)

Notes: Data are represented as the mean ± SD or n (%). The p-values refer to the overall differences across the BMI groups as derived from ANOVA (for continuous variables) or χ² tests (for categorical variables). *P<0.05, **P<0.01.

Abbreviations: Hb, hemoglobin; BMI, body mass index; GDM, gestational diabetes mellitus; SBP, systolic blood pressure; DBP, diastolic blood pressure; OGTT, oral glucose tolerance test; FPG, fasting plasma glucose; 1hPG, one-hour postprandial glucose; 2hPG, two-hour postprandial glucose.

Table 2 Association of Maternal Pre-Pregnancy Hemoglobin Levels with GDM Risk in the Overall Population

Variables	GDM/Total (%)	Model 1^†			Model 2^‡
		OR	95% CI	P	OR	95% CI	P
Pre-pregnancy hemoglobin level (g/L)
<118	33/362(9.1)		Reference			Reference
118–122.9	45/310(14.5)	1.69	1.05–2.37	0.031	1.705	1.05–2.76	0.03
123–130	51/337(15.1)	1.78	1.12–2.83	0.015	1.709	1.07–2.73	0.025
≥130	58/280(20.7)	2.60	1.64–4.13	<0.001	2.64	1.66–4.19	<0.001
Trend test		<0.001			<0.001

Notes: ^†Univariate model. ^‡Adjusted for age, pre-pregnancy BMI, pre-pregnancy systolic blood pressure, pre-pregnancy diastolic blood pressure, smoking exposure, family history of diabetes, alcohol consumption.

Figure 1 The association of maternal pre-pregnancy Hb with GDM risk.

Notes: RCS regression analysis of pre-pregnancy hemoglobin levels with GDM risk. Hemoglobin 123 g/L was selected as the reference level. The lines indicate estimated ORs, and the light blue areas represent 95% CI.

Table 3 Association of Pre-Pregnancy BMI with GDM Risk in the Overall Population

Variables	GDM/Total (%)	Model 1^†			Model 2^‡
		OR	95% CI	P	OR	95% CI	P
Pre-pregnancy BMI (kg/m^2)
<18.5	11/180(4.9)		Reference			Reference
18.5–24.9	120/944(12.7)	2.24	1.18–4.24	0.014	1.89	0.98–3.65	0.056
25.0–29.9	47/137(34.3)	8.02	3.97–16.23	<0.001	5.96	2.84–12.47	<0.001
≥30	9/28(32.1)	7.28	2.68–19.79	<0.001	4.19	1.41–12.45	0.01
Trend test		<0.001			<0.001

Notes: ^†Univariate model. ^‡Adjusted for age, pre-pregnancy hemoglobin levels, pre-pregnancy systolic blood pressure, pre-pregnancy diastolic blood pressure, smoking exposure, family history of diabetes, alcohol consumption.

Table 4 Association of Pre-Pregnancy BMI with GDM Risk Based on Different Pre-Pregnancy Hemoglobin Levels

Variables		GDM/Total (%)	Model 1^†			Model 2^‡
			OR	95% CI	P	OR	95% CI	P
Pre-pregnancy hemoglobin level (g/L)<123	Pre-pregnancy BMI (kg/m^2)
	<18.5	5/102(4.9)			Reference		Reference
	18.5–24.9	41/411(9.9)	2.15	0.83–5.58	0.116	2.13	0.82–5.55	0.123
	25.0–29.9	14/46(30.4)	8.49	2.84–25.41	<0.001	9.28	3.01–28.6	<0.001
	≥30	1/10(10)	2.16	0.23–20.51	0.504	2.09	0.21–20.65	0.530
Pre-pregnancy hemoglobin level (g/L)≥123	Pre-pregnancy BMI (kg/m^2)
	<18.5	6/78(7.7)			Reference		Reference
	18.5–24.9	79/533(14.8)	2.09	0.88–4.95	0.960	2.04	0.84–4.99	0.117
	25.0–29.9	33/91(36.3)	6.83	2.68–17.41	<0.001	7.06	2.66–18.61	<0.001
	≥30	8/180(44)	9.60	2.76–33.45	<0.001	10.77	2.85–40.63	<0.001

Notes: ^†Univariate model. ^‡Adjusted for age, pre-pregnancy systolic blood pressure, pre-pregnancy diastolic blood pressure, smoking exposure, family history of diabetes, alcohol consumption.

Figure 2 The association of pre-pregnancy BMI with GDM risk based on different pre-pregnancy Hb levels.

Notes: RCS regression analysis of pre-pregnancy BMI with GDM risk through stratified analyses modified by pre-pregnancy hemoglobin levels < 123 g/L (A) and ≥ 123 g/L (B). The lines indicate estimated ORs, and the light blue areas represent 95% CI.