Estimated impact of introduction of new diagnostic criteria for gestational diabetes mellitus

Table 1 Patient characteristics per group based on classification of oral glucose tolerance test results

	n (%)	Group 1: non-GDM	Group 2: GDM by WHO 1999 only1	P value2	Group 3: GDM by WHO 2013 only	P value2	Group 4: GDM by both criteria1	P value2
n (%)	3338	2119 (63.5)	137 (4.1)		576 (17.2)		506 (15.2)
Age, yr	3336	32.3 (28.5-35.7)	34.1 (30.4-38.0)	< 0.001	33.0 (29.0-36.7)	0.002	33.6 (30.3-37.0)	< 0.001
Age group, n (%)	3336
< 30 yr		698 (33.0)	31 (22.6)	0.002	174 (30.2)	0.031	117 (23.1)	< 0.001
30-35 yr		806 (38.1)	51 (37.2)		204 (35.4)		185 (36.6)
≥ 35 yr		613 (29.0)	55 (40.1)		198 (34.4)		204 (40.3)
Prepregnancy BMI, kg/m2	3156	24.3 (21.8-27.9)	24.7 (22.7-28.7)	0.072	29.0 (24.5-33.6)	< 0.001	28.0 (24.2-32.3)	< 0.001
Prepregnancy BMI group, n (%)	3156
< 30 kg/m2		1669 (83.7)	104 (80.6)	0.598	309 (56.6)	< 0.001	314 (64.5)	< 0.001
≥ 30-< 35 kg/m2		207 (10.4)	18 (14.0)		133 (24.4)		102 (20.9)
≥ 35 kg/m2		118 (5.9)	7 (5.4)		104 (19.0)		71 (14.6)
Ethnicity, n (%)	3248
Caucasian		1126 (54.8)	69 (51.1)	0.402	292 (51.7)	0.378	241 (48.7)	0.030
Mediterranean		616 (30.0)	40 (29.6)		176 (31.2)		166 (33.5)
African, Caribbean		72 (3.5)	3 (2.2)		19 (3.4)		17 (3.4)
Asian		53 (2.6)	7 (5.2)		16 (2.8)		22 (4.4)
Hindustan		37 (1.8)	3 (2.2)		18 (3.2)		15 (3.0)
Other		150 (7.1)	13 (9.5)		44 (7.6)		34 (6.7)
Gravidity	3336	2 (1-3)	2 (1-3)	0.368	2 (2-4)	< 0.001	2 (2-3)	0.045
Parity, n (%)	3323
0		803 (37.9)	46 (33.6)	0.102	171 (29.7)	< 0.001	169 (33.4)	0.010
1		785 (37.0)	48 (35.0)		231 (40.1)		183 (36.2)
≥ 2		519 (24.9)	43 (31.4)		173 (30.0)		152 (30.0)
Smoking during pregnancy, n (%)	3270	277 (13.3)	15 (11.1)	0.470	94 (16.8)	0.031	79 (16.1)	0.104
Conception spontaneous, n (%)	3277	1866 (89.8)	120 (88.9)	0.748	496 (87.9)	0.216	431 (86.4)	0.029
Multiple pregnancy, n (%)	3336	84 (4.0)	9 (6.6)	0.138	10 (1.7)	0.010	33 (6.5)	0.012
Gestational age at OGTT, wk	3336	27.1 (25.1-29.6)	28.1 (25.4-32.7)	0.041	27.0 (24.6-29.1)	< 0.001	27.0 (23.9-29.7)	< 0.001
OGTT fasting plasma glucose value, mmol/L	3336	4.6 (4.4-4.8)	4.7 (4.5-4.8)	0.087	5.2 (5.1-5.4)	< 0.001	5.4 (5.0-5.8)	< 0.001
OGTT 2-h post load glucose value, mmol/L	3298	5.7 (4.9-6.4)	8.0 (7.8-8.2)	< 0.001	6.4 (5.7-6.9)	< 0.001	8.7 (8.1-9.6)	< 0.001

Continuous variables are presented as mean ± SD or median (interquartile range). Percentages may not add up to 100% due to rounding.

¹Women in this group received treatment for gestational diabetes mellitus.

²P value reported compared to group 1: non-gestational diabetes mellitus.

GDM: Gestational diabetes mellitus; BMI: Body mass index; OGTT: Oral glucose tolerance test; WHO: World Health Organization.

Table 2 Pregnancy outcomes per group based on classification of oral glucose tolerance test results

	n	Group 1: non-GDM	Group 2: GDM by WHO 1999 only1	P value2	Group 3: GDM by WHO 2013 only	P value2	Group 4: GDM by both criteria1	P value2
n (%)	3338	2119 (63.5)	137 (4.1)		576 (17.2)		506 (15.2)
Maternal
Highest diastolic blood pressure, mmHg	3103	75 (70-82)	80 (70-85)	0.060	80 (75-85)	< 0.001	80 (75-85)	< 0.001
Highest diastolic blood pressure, n (%)	3103
< 90 mmHg		1691 (86.1)	111 (84.1)	0.520	429 (81.4)	0.007	379 (79.0)	< 0.001
≥ 90 mmHg		273 (13.9)	21 (15.9)	0.520	98 (18.6)	0.007	101 (21.0)	< 0.001
≥ 110 mmHg		31 (1.6)	3 (2.3)	0.541	4 (0.8)	0.156	7 (1.5)	0.849
Induction of labor, n (%)	3044	335 (17.4)	38 (28.8)	0.001	97 (19.0)	0.390	155 (32.6)	< 0.001
Planned caesarean, n (%)	3044	213 (11.1)	17 (12.9)	0.520	79 (15.5)	0.006	81 (17.1)	< 0.001
Assisted vaginal delivery, n (%)	3059	124 (6.4)	9 (6.8)	0.853	29 (5.6)	0.517	17 (3.6)	0.018
Emergency caesarean, n (%)	3059	223 (11.5)	12 (9.1)	0.394	65 (12.6)	0.492	65 (13.6)	0.205
Blood loss > 1000 cc, n (%)	3019	173 (9.1)	15 (11.4)	0.374	35 (6.9)	0.131	41 (8.7)	0.813
Neonatal
Gestational age at delivery, wk	3070	40.0 (39.0-40.9)	39.4 (38.3-40.6)	0.001	39.9 (38.7-41.0)	0.515	39.1 (38.1-40.0)	< 0.001
Preterm birth, n (%)	3070
Spontaneous		79 (4.1)	7 (5.3)	0.491	26 (5.0)	0.337	33 (6.9)	0.008
Indicated		6 (0.3)	1 (0.8)	0.370	6 (1.2)	0.024	7 (1.5)	0.006
Birth weight, grams	3186	3490 (3090-3840)	3449 (3041-3839)	0.654	3598 (3216-3943)	< 0.001	3420 (2969-3800)	0.056
Birth weight, percentile	3165	50.0 (24.8-75.8)	52.0 (28.8-76.4)	0.388	59.9 (32.6-81.6)	< 0.001	58.7 (29.5-82.1)	< 0.001
Birth weight > 4000 grams, n (%)	3186	325 (16.2)	21 (15.0)	0.719	117 (22.3)	< 0.001	81 (15.9)	0.896
Small-for-gestational-age (< 10th percentile), n (%)	3165	160 (8.0)	6 (4.3)	0.117	28 (5.4)	0.043	34 (6.7)	0.336
Large-for-gestational-age (> 90th percentile), n (%)	3165	203 (10.2)	17 (12.2)	0.435	84 (16.2)	< 0.001	84 (16.6)	< 0.001
Admission to neonatology ward, n (%)	3146	219 (11.0)	15 (10.7)	0.904	59 (11.4)	0.813	103 (20.4)	< 0.001
Admission to NICU, n (%)	3146	75 (3.8)	4 (2.9)	0.576	22 (4.3)	0.620	28 (5.5)	0.077
Shoulder dystocia, n (%)	3173	26 (1.3)	6 (4.3)	0.015	7 (1.3)	0.935	18 (3.5)	0.001
Apgar score 5 min < 7, n (%)	3155	39 (2.0)	4 (2.9)	0.525	20 (3.9)	0.010	24 (4.7)	< 0.001

Continuous variables are presented as mean ± SD or median (interquartile range). Percentages may not add up to 100% due to rounding.

¹Women in this group received treatment for gestational diabetes mellitus.

²P value reported compared to group 1: non-gestational diabetes mellitus.

GDM: Gestational diabetes mellitus; NICU: Neonatal intensive care unit; WHO: World Health Organization.

Table 3 Likelihood ratios for adverse pregnancy outcomes for group 2-4 compared to group 1

Outcome	n (%)	LR+	95%CI	LR-	95%CI
Highest diastolic BP ≥ 90 mmHg
Non-GDM	273 (13.9)
WHO 1999 criteria only	21 (15.9)	1.16	0.74-1.82	0.99	0.96-1.02
WHO 2013 criteria only	98 (18.6)	1.31	1.08-1.58	0.92	0.86-0.98
Both criteria	101 (21.0)	1.47	1.22-1.78	0.89	0.84-0.95
Planned caesarean
Non-GDM	213 (11.1)
WHO 1999 criteria only	17 (12.9)	1.18	0.72-1.92	0.99	0.95-1.03
WHO 2013 criteria only	79 (15.5)	1.35	1.10-1.66	0.91	0.85-0.98
Both criteria	81 (17.1)	1.47	1.20-1.81	0.89	0.83-0.96
Assisted vaginal delivery
Non-GDM	124 (6.4)
WHO 1999 criteria only	9 (6.8)	1.06	0.55-2.05	1.00	0.95-1.04
WHO 2013 criteria only	29 (5.6)	0.90	0.64-1.26	1.03	0.95-1.11
Both criteria	17 (3.6)	0.59	0.38-0.93	1.10	1.03-1.18
Emergency caesarean
Non-GDM	223 (11.5)
WHO 1999 criteria only	12 (9.1)	0.78	0.44-1.39	1.02	0.98-1.05
WHO 2013 criteria only	65 (12.6)	1.09	0.86-1.37	0.98	0.91-1.04
Both criteria	65 (13.6)	1.16	0.92-1.46	0.96	0.90-1.03
Preterm birth
Non-GDM	87 (4.5)
WHO 1999 criteria only	8 (6.1)	1.35	0.68-2.67	0.98	0.92-1.04
WHO 2013 criteria only	32 (6.2)	1.30	0.96-1.77	0.92	0.82-1.03
Both criteria	41 (8.6)	1.68	1.29-2.19	0.84	0.74-0.95
SGA
Non-GDM	160 (8.0)
WHO 1999 criteria only	6 (4.3)	0.54	0.24-1.20	1.03	1.00-1.07
WHO 2013 criteria only	28 (5.4)	0.71	0.50-1.00	1.08	1.01-1.15
Both criteria	34 (6.7)	0.86	0.63-1.18	1.04	0.97-1.11
Birth weight > 4000 g
Non-GDM	325 (16.2)
WHO 1999 criteria only	21 (15.0)	0.92	0.59-1.44	1.01	0.98-1.04
WHO 2013 criteria only	117 (22.3)	1.36	1.14-1.63	0.91	0.86-0.97
Both criteria	81 (15.9)	0.98	0.80-1.22	1.00	0.95-1.06
LGA
Non-GDM	203 (10.2)
WHO 1999 criteria only	17 (12.2)	1.22	0.75-1.98	0.99	0.95-1.03
WHO 2013 criteria only	84 (16.2)	1.50	1.23-1.83	0.88	0.81-0.95
Both criteria	84 (16.6)	1.54	1.26-1.87	0.87	0.81-0.94
Admission to NICU
Non-GDM	75 (3.8)
WHO 1999 criteria only	4 (2.9)	0.76	0.29-2.00	1.02	0.97-1.07
WHO 2013 criteria only	22 (4.3)	1.10	0.76-1.60	0.97	0.87-1.09
Both criteria	28 (5.5)	1.36	0.98-1.88	0.91	0.81-1.03
Shoulder dystocia
Non-GDM	26 (1.3)
WHO 1999 criteria only	6 (4.3)	2.95	1.41-6.19	0.87	0.73-1.03
WHO 2013 criteria only	7 (1.3)	1.03	0.53-1.99	0.99	0.83-1.19
Both criteria	18 (3.5)	2.06	1.43-2.96	0.74	0.58-0.94
5-min Apgar score < 7
Non-GDM	39 (2.0)
WHO 1999 criteria only	4 (2.9)	1.43	0.55-3.68	0.97	0.88-1.07
WHO 2013 criteria only	20 (3.9)	1.67	1.16-2.41	0.83	0.69-1.00
Both criteria	24 (4.7)	1.92	1.39-2.66	0.77	0.64-0.94

LR+: Positive likelihood ratio; 95%CI: 95% confidence interval; LR-: Negative likelihood ratio; GDM: Gestational diabetes mellitus; BP: Blood pressure; SGA: Small-for-gestational-age; LGA: Large-for-gestational-age; WHO: World Health Organization; NICU: Neonatal intensive care unit.