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Table 3 Oxytocin levels in blood samples collected during physiological birth in the 20 selected papers. Values from pregnant and non-pregnant women are included. All values are presented in pg/mL, with SD or range in parentheses

From: Maternal plasma levels of oxytocin during physiological childbirth – a systematic review with implications for uterine contractions and central actions of oxytocin

First author, year Labour and birth (pg/mL) Time for blood sample Pregnancy (pg/mL) Gestational week (w) Non-pregnant (pg/mL)
Coch 1965 [13]a 167 Active labour    
Kumaresan 1974 [14]a 302 (58.3–725.0) Active labour 110 4 w < 1.7
   275 40 w  
Kumaresan 1975 [15]a 150.0 (18.3) 10 min before birth    
136.7 (20.0) Immediately after birth    
Gibbens 1976 [16]a 4.2–20.8 1st – 3rd stage    
Vasicka 1978 [17]a 73.3–273.3 Active labour 211.5 (35.2) 24 w  
   255.0 (44.3) 40 w  
Dawood 1979 [18] 0–86 1st stage of labour 17.9 (2.1) 1–20 w  
   28.9 (4.7) 21–30 w  
   32.9 (2.9) 31–32 w  
   26.4 (4.8) 38 w  
   74.2 (14.2) 39 w  
Leake 1981 [19]a 2.2 (0.3 Latent phase 2.2 (0.2) 15–42 w 2.3 (0.3)
2.7 (0.3) Active labour    
1.8 (0.2) Visible head    
7.0 (1.8) Delivery of head    
Otsuki 1983 [20]a 21.0 (63.3–146.7) Active labour 8.3 20 w  
   20.8 (12.8) 36–41 w  
Goodfellow 1983 [21] 7.2–46.0; Full dilatation    
8.8–85.0c Crowning of head    
Husslein 1983 [22] 50.7 (10.7) 29.1 (9.7) Full dilatation 30 min postpartum    
Fuchs 1983 [23] 45 (3.9) 21.1 (6.4) 49.1 (10.9) 58.8 (9.9) 110 (22.7) 1st stage 1–3 mU/min SOT inf 4–6 mU/min SOT inf 7–9 mU/min SOT inf 10–15 mU/min SOT inf 15.4 (8.7) 17.4 (4.8) 19.9 (3.1) 1–2 weeks before labour Before induction At term  
Amico 1984 [24]a 1.7 (0.5) Arrest in active labour    
Takeda 1985 [25]a 32.8 (5.5) Active labour 26.8 (4.8) 7–41 w 8.0 (0.8)
Takagi 1985 [26]a 75.3 (32.7) Before emergency CS    11.7 (8.8)
De Geest 1985 [27]a 276.7 < 3 cm cx dilatation 78.3 8–12 w  
298.3 5–7 cm 128.3 20–24 w  
281.7 10 cm 208.3 30–34 w  
276.7 2nd stage 226.7 38–42 w  
Kuwabara 1987 [28]a 51.0 (8.3) Immediately after birth 27–28 6–41 w 6.8 (0.8)
   33.3 At term  
Thornton 1988 [29]b 3.2 (2) Crowning of head    
6.4 (2) After delivery of shoulder
11.6 Mean peak after birth
Oosterbaan 1989 [30] 65 (9) 12 (9) Immediately after birth During prelabour CS    
Fuchs 1991 [31]a 1.8 (0.2) 1st stage < 6 cm 1.5 (0.5) At term before elective CS  
2.3 (0.6) 2nd and 3rd stage    
Stoche 2001 [32] 7.4 (2.1) 1st stage    
6.6 (3.1) Before analgesia    
  1. pg/mL picograms per millilitre, mU/min milliunits per minute, SOT inf synthetic oxytocin infusion, CS caesarean section, μU/mL microunits per millilitre, pmol/L picomoles per litre
  2. aOxytocin levels have been converted from μU/mL to pg/mL
  3. bOxytocin levels have been converted from pmol/L (pM) to pg/mL
  4. cCorrected from Table 1 in Goodfellow 1983