Obstetric or non-obstetric surgery can be performed in pregnant women during the second trimester. We evaluated maximal sensory block level (MSBL), and other sensory block characteristics after spinal anesthesia in early and late second trimester pregnant women.

Forty-four pregnant women scheduled for cervical cerclage under spinal anesthesia in the early second trimester (Group E) or in the late second trimester (Group L) were enrolled in this study. Spinal anesthesia was performed at the L3/4 and 7 mg of 0.5% hyperbaric bupivacaine was injected into the subarachnoid space. Hemodynamic variables, incidence of nausea/vomiting, ephedrine dose, and sensory block were recorded every 2.5 min during the first 15 min and 20 min after the injection. The MSBL, the time at which MSBL was achieved, and the time to the two-segment regression of the sensory level were also recorded.

The maximum number of segments blocked was significantly greater in the Group L than in the Group E. The incidence of nausea/vomiting and hypotension, and dose of administrated ephedrine were significantly higher in the Group L than in the Group E. The mean arterial pressure during the 15 min after subarachnoid injection was significantly lower compared to the baseline value in the Group L.

The MSBL of spinal anesthesia with hyperbaric bupivacaine 7 mg were T9 in the early and T5 in the late second trimester groups. Pregnant women in the late second trimester exhibited increased incidence of hypotension and need for ephedrine than women in the early second trimester.