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International Journal of Bipolar Disorders

Table 2 Comparison of lithium serum concentrations and clinical characteristics between exposure groups

From: High lithium concentration at delivery is a potential risk factor for adverse outcomes in breastfed infants: a retrospective cohort study

 

High exposure groupa

Low exposure groupa

pb

N

Mean (SD)

Median

Range

N

Mean (SD)

Median

Range

Age at follow-up (days)

7

22.1 (11.2)

26

4–40

18

25.3 (13.6)

20

8–51

0.62

Maternal dose of lithium sulfate (mg/d)

 At delivery

7

274.0 (98.3)

252

168–448

18

180.3 (84.5)

168

21–336

 < 0.05

 At follow-up

7

222.0 (56.8)

210

140–294

18

187.1 (84.4)

168

21–336

0.27

Lithium concentrations at birth

 Infant umbilical cord (meq/l)

7

0.83 (0.24)

0.90

0.60–1.20

15

0.35 (0.14)

0.40

0.1–0.5

 < 0.05

 Infant serum at 2 days of agec

4

0.68 (0.25)

0.65

0.40–1.00

9

0.38 (0.12)

0.40

0.2–0.6

 < 0.05

 Mother (meq/l)

7

0.81 (0.34)

0.80

0.40–1.50

16

0.36 (0.20)

0.40

0.1–0.7

 < 0.05

 Infant/mother ratiod

7

1.10 (0.30)

1.10

0.70–1.50

13

0.95 (0.17)

1.00

0.70–1.30

0.34

Lithium concentrations at follow-up

 Infant (meq/l)

7

0.39 (0.41)

0.20

0.10–1.20

18

0.08 (0.07)

0.06

 < 0.05 – 0.3

 < 0.05

 Mother (meq/l)

4

0.65 (0.06)

0.65

0.6–0.7

9

0.56 (0.21)

0.6

0.1–0.8

0.50

 Infant/mother ratio

4

0.48 (0.46)

0.29

0.17–1.17

9

0.17 (0.14)

0.10

0.07–0.5

0.08

 

N

n (%)

  

N

n (%)

  

p

Exclusive breastfeeding

 During hospital stay

7

3 (42.9)

  

18

8 (44.4)

  

1.0

 At follow-up

7

4 (57.1)

  

17

10 (58.8)

  

1.0

Clinical outcomese

 Symptoms at birthf

7

6 (85.7)

  

17

7 (41.2)

  

0.08

 Symptoms at follow-upg

7

2 (28.6)

  

17

2 (11.8)

  

0.55

Recommended to reduce breastfeeding at follow-up

7

2 (28.6)

  

17

1 (5.9)

  

0.18

  1. aInfants were assigned to study groups on the basis of the lower limit for therapeutic concentration, low exposure defined as infant lithium concentration < 0.6meqv/l and high exposure ≥ 0.6meqv/l
  2. bMann–Whitney U-test and Fisher’s exact tests were used to test group differences in continuous and nominal variables, respectively
  3. cMeasured in infant serum together with the neonatal screening test at median (range) 48.5 (36–62) hours of age
  4. dRatio between the lithium concentrations measured in the umbilical cord and in maternal serum at delivery
  5. eThe infant with cardiovascular malformation was excluded from the analysis of symptoms
  6. fSpecified in Table 3
  7. gSymptoms at follow-up included poor infant growth in all 4 infants and in 2 of them, one in each exposure group, also tiredness
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