From 6/8/18 to 31/12/18, 168 babies were born to 163 mothers with GDM. Of these, we excluded 62 babies: 11 preterm, 11 admitted to NICU with suspected sepsis, 10 twins, 3 with respiratory distress, one stillbirth, 8 born to mothers taking beta-blockers, two with birth weight < 2nd centile and, and 16 without a documented BG. Thus, 106 babies were included in the analysis (Fig. 1).
Characteristics of babies and their mothers are reported in Table 1. Of note, half the mothers were obese (n = 56, 52%), with just under half needing pharmacologic treatment for their GDM (n = 49, 46%). The majority of deliveries were vaginal (n = 75, 69%). One woman developed pre-eclampsia; 46 had blood loss > 500mL at delivery (23 vaginal deliveries, 23 Caesarean sections), and 7 women developed peripartum sepsis.
Table 1
Maternal baseline, GDM, labour and birth, and newborn characteristics
Characteristic
|
N
|
Total
|
Babies with hypoglycaemia*, **
|
Babies with no hypoglycaemia
|
P value
|
Mother
|
|
|
|
Age in years
|
106
|
Mean 32.3 (range 19–45)
|
32.6 years
|
32.3 years
|
0.8
|
BMI in kg/m2
|
106
|
|
|
|
|
Normal (18.5–25)
|
|
19 (18%)
|
2
|
17
|
-
|
Overweight (25.01-30)
|
|
32 (30)
|
3
|
29
|
0.9
|
Obese (> 30)
|
|
55 (52)
|
10
|
45
|
0.4
|
Parity
|
106
|
|
|
|
|
0
|
|
45 (41)
|
7
|
38
|
-
|
1 or more
|
|
61 (59)
|
8
|
53
|
0.8
|
Ethnicity
|
106
|
|
|
|
|
White Caucasian
|
|
59 (54)
|
10
|
49
|
-
|
Non-white
|
|
47 (46)
|
5
|
42
|
0.5
|
GDM
|
|
|
|
OGTT mmol/L
|
|
|
|
|
|
fasting
|
99
|
5.1 (4.0-11.5)
|
5.5 mmol/L
|
5.1 mmol/L
|
0.3
|
1-hour
|
93
|
9.7 (4.1–15.5)
|
10.3
|
9.6
|
0.2
|
2-hour
|
95
|
7.4 (3.8–13.5)
|
7.6
|
7.4
|
0.8
|
HbA1c (%)
|
100
|
5.2 (4.0-6.6)
|
5.2 %
|
5.2 %
|
0.7
|
Diabetes control
|
106
|
|
|
|
|
Diet alone
|
|
56 (52)
|
7
|
49
|
-
|
Metformin
|
|
35 (34)
|
6
|
29
|
0.5
|
Insulin (+/- metformin)
|
|
13 (12)
|
2
|
11
|
0.9
|
Labour and delivery
|
|
|
|
Onset of labour
|
106
|
|
|
|
|
Spontaneous
|
|
41 (38)
|
4
|
37
|
-
|
Induced
|
|
44 (42)
|
8
|
36
|
0.3
|
No labour
|
|
21 (20)
|
3
|
18
|
0.6
|
Intrapartum BG
|
99
|
|
|
|
|
Self
|
|
91 (92)
|
11
|
80
|
-
|
Variable rate insulin intravenous infusion
|
|
8 (8)
|
2
|
6
|
0.3
|
Mode of delivery
|
106
|
|
|
|
|
Vaginal spontaneous
|
|
60 (57)
|
7
|
53
|
|
Vaginal assisted
|
|
14 (13)
|
3
|
11
|
0.3
|
Caesarean section
|
|
32 (30)
|
5
|
27
|
0.6
|
Neonatal characteristics
|
|
|
|
Sex
|
106
|
|
|
|
|
Male
|
|
58 (55)
|
8
|
50
|
0.9
|
Gestational age at delivery
|
106
|
275 days (range 259–290)
|
278
|
275
|
0.1
|
Birthweight
|
106
|
|
|
|
|
> 90th centile
|
|
24 (23)
|
0
|
24
|
-
|
< 10th centile
|
|
5 (5)
|
0
|
5
|
-
|
Feeding characteristics
|
|
|
|
Mode of first feed
|
103
|
|
|
|
|
Breast
|
|
92 (89)
|
14
|
78
|
0.4
|
*Hypoglycaemia as per pragmatic definition including biochemical and clinical signs. ** N unless units given |
The mean gestational age at birth was 39.3 weeks and mean birth weight was 3455g (Standard Deviation (SD) 486g). The first feed was breastmilk for 93% of babies.
All 106 babies had a BG measurement before their second feed. After the first BG, 38 babies had one further measurement (two measurements in total), 20 babies had two further measurements, and 12 babies had more than three further BG measurements.
Patterns of Neonatal hypoglycaemia
Thirteen babies developed measured hypoglycaemia (BG ≤ 2.0mmol/L) in the first 24 hours and a further two babies were treated with buccal dextrose due to clinical signs of hypoglycaemia (i.e. 15 babies in total with clinical or biochemical hypoglycaemia). Five recovered without any treatment. One of these babies had hypoglycaemia persisting after 24-hours of age despite treatment with buccal dextrose. There were no cases of severe hypoglycaemia (BG ≤ 1.0).
Out of the 13 babies with measured hypoglycaemia in the first 24-hours, 11 were detected at the first BG, one was detected at the second test, and one at the third test. Both these babies with later detection had initial BG ≤ 2.6 and according to the protocol in place at the time, they had the second and third BG done. It was noted that both mothers of the babies detected at the second and third tests had significant psychiatric co-morbidities.
There were two cases of persistent hypoglycaemias (BG ≤ 2.0mmol/L detected on three or more measurements). One of these babies was identified at first BG (1.4mmol/L) and admitted to neonatal unit for intravenous (IV) dextrose. The other baby had persistent hypoglycaemia after 24 hours. Her mother had a history of anxiety and other comorbidities who had declined antenatal breast-feeding support. She was admitted to NICU for monitoring and recovered with buccal dextrose.
The remaining 91 babies had neither biochemically recorded hypoglycaemia nor received treatment for clinical suspicion of hypoglycaemia.
Nine babies were admitted to NICU, including four (of the 15) babies who had hypoglycaemia, and one baby for hypoxia, jaundice, bradycardia, poor tone and maternal sepsis respectively.
There were 11 readmissions during the first 6 weeks of life but no readmissions due to hypoglycaemia.
Clinical risk factors for neonatal hypoglycaemia
No maternal, birth or newborn risk factors were associated with neonatal hypoglycaemia in this study population (Table 1), therefore multivariate analysis was not performed.
The results of the first capillary BG result for newborns performed before the second feed are presented in Fig. 2. There were 42 babies with a reading ≤ 2.6mmol/L at the first test. This included all 15 babies diagnosed with BG ≤ 2.0mmol/L, either at this test (11 babies), or subsequently (4 babies) within the first 24-hours, with biochemical or clinical hypoglycaemia. The AUC was 0.96 (95% CI0.91-1.0) for the first neonatal BG to predict hypoglycaemia at any time during the first 24-hours of life. A threshold of 2.6mmol/L achieved 100% sensitivity, i.e. all babies with hypoglycaemia at any time in the first 24-hours had an initial BG of 2.5mmol/L or less. This result was validated in a further 65 babies born to mothers with GDM without other risk factors for hypoglycaemia who met the study entry criteria, AUC 0.99 (95% CI0.96-1.0) (Fig. 3).
Each baby with one or more episodes of hypoglycaemia had on average 4.5 tests performed, compared to 1.7 tests in the whole cohort (range 1–6), suggesting that babies at risk were correctly identified and monitored more intensely.