Fig. 3.

Uterine activity with age of pregnant myometrium. a Spontaneous force of contraction, b force of contraction under high K⁺ depolarisation, c force of spontaneous contraction normalised to high K⁺ (where high K⁺ equalled 100 %) and d oxytocin (10 nM)-induced percentage increase in integral of force (AUC), according to maternal age group. There was a small downward trend in mean force of spontaneous contraction with increasing maternal age group (a) but this was not as marked as found in non-pregnant myometrium. Maximal force achieved under high K⁺ (b) showed a small decrement with increasing maternal age however, normalised force shown in (c) did not change with advancing age, suggesting aging has little effect on myometrial function in pregnant women. Response to 10 nM oxytocin (% increase in integral of force compared to control, (d) declined with increasing maternal age group suggesting that changes in receptor expression or coupling to calcium entry and contraction may be reduced, especially beyond 40 years. Values represent means ± SEM denoted by error bars, values in parenthesis indicate n-numbers