Table 1 Characteristics of included studies

Baudesson de Chaville, 2017 [34]

Double-blind, placebo-controlled, RCT, two parallel groups

G1: MBMO (n = 16)

G2: control: an odorless diffuser (n = 17)

Total: 33.2 (31.6–34.1)

Total: 1790 (1647–1947)

Venipuncture

PIPP score

Jebreili 2015 [44]

RCT, three parallel groups

G1: MBMO (n = 45)

G2: vanilla odor (n = 45)

G3: control: routine nursing care (n = 45)

G1: 31.64 ± 2.1/1,566.9 ± 414.89

G2: 30.93 ± 2 /1,505.3 ± 409.12

G3: 31.46 ± 1.96 /1,569.8 ± 405.93

Venipuncture

PIPP score

Alemdar, 2017 [48]

RCT, four parallel groups

G1: amniotic fluid odor (n = 21)

G2: MBMO (n = 22)

G3: mother odor (n = 20)

G4: control: routine nursing care (n = 22)

G1: 33.95 ± 3.20 /2,235.04 ± 801.76

G2: 32.09 ± 3.42 /1,939.00 ± 836.78

G3: 33.05 ± 3.17 /2,120.10 ± 797.15

G4: 33.40 ± 3.11 /2,193.06 ± 679.80

Heel-stick

PIPP score

Heart rate

Oxygen saturation

Alemdar, 2020 [30]

RCT, two parallel groups

G1: amniotic fluid odor (n = 30)

G2: control: routine nursing care (n = 31)

G1: 31.30 ± 2.57 /1,734.73 ± 599.04

G2: 33.90 ± 3.17 /2,299.03 ± 758.21

Peripheral cannulation

PIPP score

Usta, 2021 [61]

Double-blind, placebo-controlled, RCT, two parallel groups

G1: lavender oil odor (n = 31)

G2: control: distilled, odorless water (n = 30)

G1: 32.45 ± 2.29 /1834.45 ± 448.51

G2: 33.10 ± 2.75 /1961.93 ± 522.82

Heel lance

PIPP-R score

Rad, 2021 [55]

Single-blind, placebo-controlled, RCT, three parallel groups

G1: MBMO (n = 30)

G2: another mother’s breast milk odor (n = 30)

G3: control: distilled water (n = 30)

G1: 32.9 ± 2.4 /1806 ± 553

G2: 30.3 ± 3.2 /1620 ± 425

G3: 32.5 ± 2.4 /1688 ± 404

HBV injection

PIPP score

Heart rate

Oxygen saturation

Asmerom, 2013 [33]

Double-blind, RCT, three parallel groups

G1: OS + NNS (n = 44)

G2: sterile water + NNS (n = 45)

G3: control: routine nursing care (n = 42)

G1: 30.1 ± 3.1 /1374.1 ± 552

G2: 31.5 ± 2.1 /1498.4 ± 706

G3: 30.5 ± 2.6 /1456.4 ± 502

Heel lance

PIPP score

Heart rate

Oxygen saturation

Dilli, 2014 [37]

Placebo-controlled, RCT, two parallel groups

G1: OS + NNS (n = 32)

G2: control: sterile water + pacifier (n = 32)

G1: 28.2 ± 2.7 /1248 ± 392

G2: 28.8 ± 2.9 /1360 ± 530

ROP screening

PIPP score

Gao, 2018 [41]

RCT, four parallel groups

G1: OS (n = 21)

G2: NNS (n = 22)

G3: OS + NNS (n = 22)

G4: control: routine nursing care (n = 21)

G1: 31.7 ± 0.9 /1780.8 ± 304.6

G2: 31.9 ± 1.1 /1767.3 ± 302.7

G3: 32.0 ± 0.8 /1697.1 ± 254.7

G4: 31.3 ± 0.6 /1682.7 ± 200.2

Heel-stick

PIPP score

Heart rate

Oxygen saturation

Liaw, 2012 [51]

RCT, three cross-over groups

G1: FT (n = 34)

G2: NNS (n = 34)

G3: control: routine nursing care (n = 34)

Total: 33.98 ± 2.0

Total: 1705.9 ± 363.3

Heel-stick

PIPP score

Sundaram, 2013 [59]

Single-blind, RCT, two cross-over groups

G1: FT (n = 20)

G2: control: routine nursing care (n = 20)

Total: 34.11 ± 2.29

Total: 2153 ± 532.84

Heel-stick

PIPP score

Alinejad-Naeini, 2014 [31]

RCT, two cross-over groups

G1: FT (n = 34)

G2: control: routine nursing care (n = 34)

Total: 29 ~ 37 weeks

Total: ≥ 1200 g

Endotracheal suctioning

PIPP score

Hill, 2005 [42]

RCT, two cross-over groups

G1: FT (n = 12)

G2: control: routine nursing care (n = 12)

Total: 28.8 ± 2.8

Total: 1410 ± 473

Routine care (nasogastric tube insertion)

PIPP score

Ward-Larson, 2004 [62]

RCT, two cross-over groups

G1: FT (n = 40)

G2: control: routine nursing care (n = 40)

Total: 27.313 ± 2.430

Total: 932.30 ± 284.05

Endotracheal suctioning

PIPP score

Davari, 2019 [36]

RCT, two cross-over groups

G1: FT (n = 40)

G2: control: routine nursing care (n = 40)

Total: 32 ~ 36 weeks

Total: ≥ 1200 g

Heel-stick

PIPP score

Apaydin, 2020 [32]

RCT, six parallel groups

G1: swaddling (n = 30)

G2: FT (n = 32)

G3: EBM (n = 31)

G4: swaddling + EBM (n = 30)

G5: FT + EBM (n = 31)

G6: control: routine nursing care (n = 33)

Total: 33.11 ± 0.84

Total: 1989.41 ± 369.51

Orogastric tube insertion

PIPP score

Heart rate

Oxygen saturation

Döra, 2021 [38]

RCT, three parallel groups

G1: white noise (n = 22)

G2: lullaby (n = 22)

G3: control: routine nursing care (n = 22)

Total: 32 ~ 37 weeks

Total: ≥ 1001 g

Venous blood collection

PIPP score

Heart rate

Oxygen saturation

Yu, 2022 [63]

Double-blind, RCT, two parallel groups

G1: maternal heart sounds (n = 32)

G2: control: routine nursing care (n = 32)

Total: < 37 weeks

Total: 1860.92 ± 506.26

Heel-stick

Heart rate

Oxygen saturation

Kahraman, 2020 [47]

RCT, four parallel groups

G1: white noise (n = 16)

G2: mothers’ voice (n = 16)

G3: MiniMuffs (n = 16)

G4: control: routine nursing care (n = 16)

G1: 33.8 ± 1.75 /1909 ± 340

G2: 34.0 ± 1.50 /1904 ± 325

G3: 34.06 ± 1.76 /2186 ± 621

G4: 34.25 ± 1.65 /2201 ± 615

Heel lance

Heart rate

Oxygen saturation

Kurdahi Badr, 2017 [50]

Double-blind, RCT, three cross-over groups

G1: lullaby (n = 42)

G2: mother's music (n = 42)

G3: control: routine nursing care + headphones (n = 42)

Total: 31.78 ± 2.8

Total: 1577 ± 499.2

Heel-stick

Heart rate

Oxygen saturation

Kucukoglu, 2016 [49]

RCT, two parallel groups

G1: white noise (n = 35)

G2: control: routine nursing care (n = 40)

G1: 31.77 ± 3.30 /1673.29 ± 321.16

G2: 31.30 ± 2.50 /1530.62 ± 347.25

HBV injection

PIPP score

Heart rate

Oxygen saturation

Taplak, 2021 [60]

RCT, four parallel groups

G1: BMO (n = 20)

G2: white noise (n = 20)

G3: FT (n = 20)

G4: control: routine nursing care (n = 20)

Total: 26 ~ 35.6 weeks

Total: ≤ 1500 g (n = 38), ≥ 1501 g (n = 42)

Endotracheal suctioning

PIPP-R score

Heart rate

Oxygen saturation

Alemdar, 2018 [29]

RCT, four parallel groups

G1: BMO (n = 32)

G2: maternal voice (n = 30)

G3: incubator cover (n = 31)

G4: control: routine nursing care (n = 32)

G1: 30.26 ± 0.69 /1430.70 ± 146.00

G2: 30.06 ± 0.63 /1460.50 ± 133.36

G3: 30.22 ± 0.66 /1404.80 ± 99.23

G4: 30.25 ± 0.50 /1503.80 ± 194.86

Peripheral cannulation

PIPP score

Mitchell, 2013 [52]

RCT, two parallel groups

G1: KC (n = 19)

G2: control: routine nursing care (n = 19)

Total: 27 ~ 30 weeks

G1: 1311.5 ± 216.3

G2: 1213.2 ± 186.4

Routine care (suctioning via tracheal or nasal routes)

PIPP score

Cong, 2011 [35]

RCT, two cross-over groups

G1: KC (n = 10)

G2: control: routine nursing care (n = 10)

Total: 30 ~ 32 weeks

Total: 1577 ± 327

Heel-stick

PIPP score

Srivastava, 2022 [58]

Open label, RCT, two parallel groups

G1: KMC (n = 40)

G2: control: routine nursing care (n = 40)

Total: 28 ~ 37 weeks

Total: 1500-2499 g

Orogastric tube insertion

PIPP-R score

Johnston, 2008 [46]

Single-blind, RCT, two cross-over groups

G1: KMC (n = 61)

G2: control: routine nursing care (n = 61)

Total: 28 0/7 ~ 31 0/7 weeks

Heel lance

PIPP score

Johnston, 2013 [45]

RCT, two parallel groups

G1: therapeutic touch (n = 27)

G2: control: routine nursing care (n = 28)

Total: 26 0/7 ~ 28 6/7 weeks

G1: 974.54 ± 188

G2: 977.44 ± 210

Heel lance

PIPP score

Fatollahzade, 2022 [40]

RCT, two cross-over groups

G1: GHT (n = 34)

G2: control: routine nursing care (n = 34)

Total: 27 ~ 34 weeks

Total: ≥ 1200 g

Endotracheal suctioning

PIPP score

Sezer Efe, 2022 [56]

Assessor-blind, RCT, two parallel groups

G1: GHT (n = 25)

G2: control: routine nursing care (n = 25)

G1: 34.95 ± 1.61 /2272.70 ± 430.19

G2: 35.3 ± 1.83 /2289.37 ± 630.80

Heel lance

Heart rate

Oxygen saturation

Dur, 2020 [39]

RCT, three parallel groups

G1: GHT (n = 30)

G2: Yakson touch (n = 30)

G3: control: routine nursing care + pacifier (n = 30)

Total: 33.44 ± 1.74

Total: 1960.83 ± 413.75

Heel lance

Heart rate

Oxygen saturation

Jain, 2006 [43]

Double-blind, RCT, two cross-over groups

G1: massage (n = 23)

G2: control: routine nursing care (n = 23)

Total: 31.1 ± 1.9

Total: 1693 ± 396

Heel-stick

Heart rate

Oxygen saturation

Qiu, 2017 [54]

RCT, two parallel groups

G1: music + GHT (n = 30)

G2: control: routine nursing care (n = 32)

G1: 34.30 ± 0.67 /1930 ± 130

G2: 33.33 ± 0.54 /2000 ± 70

Routine care (tracheal aspiration, nasal aspiration, removal of intravenous lines, etc.)

PIPP score

Shukla, 2018 [57]

Double-blind, RCT, four parallel groups

G1: KMC (n = 50)

G2: music therapy (n = 49)

G3: KMC + music therapy (n = 50)

G4: control: routine nursing care (n = 51)

Total: 34.0 ± 2.32

Total: 1910 ± 340

Heel prick

PIPP score

Perroteau 2018 [53]

RCT, two parallel groups

G1: FT + NNS (n = 30)

G2: control: routine nursing care + pacifier (n = 29)

Total: 29.0 (28.0–31.0)

Total: 1300.0 (1130.0–1530.0)

Heel-stick

PIPP score