Comparison between D/H ratios of simply deuterated molecules, including the respective statistical corrections (see text), for several early-stage star-forming sources. Data are colour-coded corresponding to the different molecules shown in the legend. Filled symbols represent direct detections of the corresponding deuterated molecule. Open symbols represent the upper limits. Circles represent data obtained with single-dish observations. Triangles represent data obtained with interferometric observations. Dashed grey lines are a guide to distinguishing different star-forming stages. Notes: References per source: Starless cores GEMS sample: This work and Esplugues et al. (2022). B10-6 to B10-17 starless cores in Taurus: Ambrose et al. (2021). L1544: Chacón-Tanarro et al. (2019), Spezzano et al. (2022b), and Giers et al. (2022). TMC1: Minowa et al. (1997) and Turner (2001). L134N/L183: Turner (2001). CB23, L1400A, L1400K, L1495, L1495AN, L1495AS, L1495B, L1512, L1517B, and TMC2: Chantzos et al. (2018). B1b: This work, Marcelino et al. (2005), and Turner (2001). L483: Agúndez et al. (2019) and Jensen et al. (2021). IRAS2/IRAS2A: Coutens et al. (2014), Liu et al. (2011), Parise et al. (2006), and Taquet et al. (2013a). IRAS4A/IRAS4A DCO⁺/IRAS4A interferometry: Parise et al. (2006), Taquet et al. (2013a), Taquet et al. (2019), and Vastel et al. (2003). IRAS4B: Parise et al. (2006) and Persson et al. (2014). L1448N/L1448mm: Parise et al. (2006). L1157mm: Parise et al. (2006). L1527: Parise et al. (2006), Sakai et al. (2009), and Yoshida et al. (2019). IRAS16293: Butner et al. (2007), Coutens et al. (2012), Drozdovskaya et al. (2018), Parise et al. (2006), van Dishoeck et al. (1995), Vastel et al. (2003), and Chantzos et al. (2018). IRAS16293A: Drozdovskaya et al. (2022), Manigand et al. (2020), and Persson et al. (2013). IRAS16293 B: Drozdovskaya et al. (2022), Jørgensen et al. (2018), and Persson et al. (2018). B335: Jensen et al. (2021). HH212: Bianchi et al. (2017b) and Taquet et al. (2019). BHR71-IRS1: Jensen et al. (2019). L1689 DCO⁺: Vastel et al. (2003). Per5, HH211, L1448IRS2, IRAS03282, and L1521F: Chantzos et al. (2018). SVS13A: Bianchi et al. (2017a, 2019). G10.47+0.03, G31.41+0.31, and G34.26+0.15: Hatchell et al. (1999). Orion KL: Bergin et al. (2002), Crockett et al. (2014), Lis et al. (2002), Taquet et al. (2019), and Turner (1990). NGC7129 FIRS2: Fuente et al. (2014). Sgr B2: Belloche et al. (2016). NGC 6334 MM1I: Bøgelund et al. (2018). G328.2551-0.5321/G328.2551-0.5321 warm: Bouscasse et al. (2022). AFGL5142, IRAS 05358+3543, and G5.89-0.39: Zahorecz et al. (2017, 2021). G028-C1, G034-F2, G034-G2, 18089-1732, 18517+0437, G75-core, I19035-VLA1, and 19410+2336: Zahorecz et al. (2021).