Background: KV7 voltage gated potassium channels formed by the combination of KCNQ-encoded, pore-forming α-subunits (KV7.1-7.5) and KCNE-encoded, regulatory β-subunits (KCNE1-5) play an important role in regulating smooth muscle resting membrane potential and contractile activity. The aims of this study were to characterise the mRNA and protein expression of KCNQ1-5 and KCNE1-5 and determine the functional impact of a comprehensive panel of KV7-modulating compounds.Methods: Myometrial tissue was obtained, with informed written consent, from pregnant women undergoing elective Caesarean section at term (> 37 weeks’, not in labour, n=28). KCNQ1-5 and KCNE1-5 mRNA expression was measured by qRT-PCR and normalised to 3 housekeeper genes. KV7 α (7.1, 7.3 and 7.4) and β (KCNE1, 3 and 4) subunits were detected using immunohistochemistry (IHC). Spontaneous contractile activity [mean integral tension (MIT), contraction frequency and amplitude] was measured in isolated myometrial strips (n=3-7) and the effect of KV7 blockers (XE991, 20 µM; chromanol 293B, 20 µM) and activators (retigabine, 20 µM; ML213, 20 µM; ICA060973, 20 µM; acrylamide S-1, 10 µM) was compared to vehicle controls (DMSO).Results: All KCNQ and KCNE isoforms were detected in myometrial tissue with KCNQ4 (Q4>>Q1>Q3>Q2>Q5) and KCNE4 (E4>>E3<E5<E1<E2) being the most highly expressed isoforms (p<0.01). Protein for KCNQ1, 3 and 4 as well KCNE1, 3 and 4 were detected and localised to myometrial smooth muscle. The KV7-selective activators retigabine and S-1 significantly relaxed spontaneous contractions vs vehicle (mean MIT ±SEM: 25.3 ± 3.89%, 19.95 ± 8.73% vs 99.18 ± 2.59%, 94.64 ± 11.03%; p=0.006, p=0.016 respectively). ICA069673 decreased MIT vs vehicle controls (27.74 ± 14.96% vs 102.2 ± 12.24%). The KV7.2/7.4-preferential activator ML213 also appeared to decrease MIT, but this did not reach significance (p=0.057). XE991 did not affect MIT but contraction frequency was increased (210 ± 16.32% vs 112.3 ± 7.18%, p=0.008) and amplitude was suppressed (77.15 ± 4.9% vs 104.9% ± 7.24%, p=0.016). Chromanol 293B had no effect on contractility vs control (p=0.191).Conclusions: These molecular data indicate that Kv7 channel subunits are expressed at mRNA and protein, forming functional channels. The relaxation induced by Kv7 activation highlights the importance of these channels in modulation of uterine excitability during gestation and parturition.