Cholinesterase activity in pregnant women and newborns.

Plasma and red blood cell cholinesterase activity in blood samples from 259 pregnant women and cord blood from some of their newborn were compared with samples from 25 nonpregnant female volunteers and with laboratory norms (Ellman method). Plasma cholinesterase was significantly lower (p < 0.05) and red blood cell cholinesterase higher (p < 0.05) in pregnant women than in nonpregnant controls in a repeated measures analysis. By the sixth post-partum week, both plasma and red blood cell cholinesterase were similar to nonpregnant control activity. Fetal cord red blood cell cholinesterase activity was also lower than in nonpregnant women, but plasma levels were not significantly different. When compared with standard laboratory normal ranges, most (98-100%) plasma cholinesterase values in pregnant women and newborn were within range, whereas the majority (59-87%, depending on trimester) of red blood cell levels were above range in pregnancy and below range in 53% of newborns. A low red blood cell cholinesterase in pregnant women is more consistent with a possible overexposure to anticholinesterases than a low plasma cholinesterase. Periods of altered sensitivity to specific cholinesterase inhibiting drugs and environmental agents are suggested by these findings.