The levator ani (LA) is a muscle of evacuation and acts as well to support the pelvic viscera. An increase of the intraabdominal pressure beyond the physiologic limits and visceral overload are speculated to interfere with LA functional activity. This consideration was a stimulus to study the effect of pregnancy on the LA muscle. The EMG activity of the LA muscle was recorded before and during pregnancy and after delivery in 36 women (mean age 27.2 ± 3.1 years, 20 multigravida, 16 primigravida). A needle electrode was inserted into the muscle and LA activity was recorded at rest, and on squeezing and straining in both the erect and recumbent position. In the erect position, the resting and squeezing EMG activity during the first 8 weeks of pregnancy, showed no significant difference (p>0.05) from that before pregnancy, and after that, increased progressively and significantly until delivery. On straining, the EMG activity showed no significant difference from that before pregnancy in the first 8 weeks, and after that, decreased progressively and significantly till delivery. In the recumbent position, the LA EMG registered similar activity to that in the erect position but with significantly lower values (p<0.05). The reduction in the LA EMG activity was more evident in the multi- than in the primi-gravida. In the postpartum period, no LA EMG activity was recorded in the first month; the activity increased progressively after that time to reach the pre-pregnancy level in the forth postpartum month. In conclusion, pregnancy interferes with EMG and functional activity of the LA from the 8th week onwards due to the progressively increasing size and weight of the uterus. This effect was most marked in the last 12 weeks. Delivery seems to maximally inhibit the LA activity in the first postpartum month. Excessive LA traumatization may eventually lead to levator dysfunction syndrome.
Keywords: Pelvic floor, electric waves, levator dysfunction, squeeze, strain, primi-, multi-gravida