Table 1 Characteristics of overall sample and comparison between groups with and without NAS

Maternal age – mean ± SD [years]

31.4 ± 5.1

31.3 ± 5.2

31.6 ± 5.1

0.753

Primipara - n (%)

24 (30.4)

14 (34.1)

10 (26.3)

0.366

Drugs - n (%)

0.019

 One

19 (24.1)

5 (14.7)

14 (40.0)

 Two or more

50 (63.3)

29 (85.3)

21 (60.0)

Drugs - n (%)*

 Heroin

60 (75.9)

35 (97.2)

25 (69.4)

0.006

 Cocaine

49 (62.0)

26 (65.0)

21 (53.8)

0.426

 Cannabinoids

21 (26.6)

8 (23.5)

13 (37.1)

0.657

Substitution therapy - n (%)

 None

10 (2.7)

1 (2.5)

9 (23.1)

0.021

 Methadone

53 (67.1)

32 (80.0)

21 (53.8)

0.039

 Buprenorphine

16 (20.2)

7 (17.5)

9 (23.1)

1.000

Other abuses - n (%)

 Tobacco

58 (73.4)

30 (96.8)

28 (82.4)

0.107

 Alcohol

3 (3.8)

0 (0.0)

3 (11.5)

0.236

Chronic medication - n (%)*

 Psychiatric

  Benzodiazepine

20 (25.3)

15 (39.5)

5 (12.8)

0.064

  Antidepressant

18 (22.8)

10 (26.3)

8 (20.5)

1.000

  Antipsychotic

9 (11.4)

5 (13.2)

4 (10.3)

1.000

 Other

  Antiretroviral

5 (6.3)

3 (7.9)

0 (0.0)

1.000

  Anticonvulsant

3 (3.8)

0 (0.0)

1 (2.6)

1.000

  Antihistamine

2 (2.5)

3 (7.9)

2 (5.1)

1.000

  Anticholinergic

1 (1.3)

1 (2.6)

0 (0.0)

0.952

  Corticoids

1 (1.3)

1 (2.6)

0 (0.0)

0.952

Gestational diabetes - n (%)

6 (7.6)

2 (5.0)

4 (10.3)

0.432

TORCH infection - n (%)

39 (49.4)

23 (57.5)

16 (41.0)

0.143

HCV infection - n (%)

38 (48.1)

23 (57.5)

15 (38.5)

0.090

Education level - n (%)

0.443

 Lower Secondary

17 (21.5)

9 (45.0)

8 (53.3)

 Upper Secondary

16 (20.2)

9 (45.0)

7 (46.7)

 Tertiary

2 (2.5)

2 (10.0)

0 (0.0)

Perinatal characteristics

Cesarean delivery - n (%)

22 (27.8)

11 (27.5)

11 (28.2)

0.944

Gestational age - median (IQR) [weeks]

38.3 (35–41)

38.2 (35–41)

38.3 (35–41)

0.911

Birthweight - mean ± SD [gram]

2704 ± 486

2649 ± 456

2761 ± 514

0.306

Male - n (%)

41 (51.9)

20 (48.8)

21 (55.3)

0.732

5-minute Apgar score < 7 - n (%)

0 (0.0)

0 (0.0)

0 (0.0)

-

Neonatal characteristics

Length of stay - median (IQR) [days]

7.0 (2–36)

8.5 (4–33)

6.0 (2–36)

0.029

NICU admission - n (%)

28 (35.4)

20 (50.0)

31 (79.5)

0.006

 NAS as main cause

1 (1.3)

1 (5.0)

0 (0.0)

Length of stay at NICU - median (IQR) [days]

7.5 (1–33)

7.0 (1–31)

8.5 (1–33)

0.582

Breastfeeding - n (%)

62 (78.5)

31 (77.5)

31 (79.5)

0.830

 Exclusive

33 (53.2)

12 (30.0)

21 (53.8)

0.032

Maximum weight loss from birthweight - mean ± SD [%]

8.3 ± 3.6

9.0 ± 3.2

7.5 ± 4.0

0.062

Comorbidities - n (%)

13 (16.5)

7 (17.9)

6 (15.4)

0.761

Long-term outcomes

Follow-up time - median (IQR)

8.0 (1–12)

9.0 (1–12)

7.0 (1–12)

0.029

Neurodevelopmental outcomes - n (%)

 Neuropsychomotor developmental delay

11 (13.9)

5 (12.5)

6 (15.4)

1.000

 Specific learning disability

1 (1.3)

1 (2.5)

0 (0.0)

1.000

 Cerebral palsy

1 (1.3)

0 (0.0)

1 (2.6)

1.000

 Autism spectrum disorder

2 (2.6)

1 (2.5)

1 (2.6)

1.000

 Attention deficit hyperactivity disorder

9 (11.4)

6 (15.0)

3 (7.7)

1.000