Pigmentary demarcation lines of pregnancy with erythema.

We describe two patients with pregnancy-associated pigmentary demarcation lines overlapped by erythematous changes. In both cases, there was a symmetrical well-defined erythematous pigmentation involving the buttocks and flexor aspects of the legs. After normal delivery the erythema disappeared within 7-10 days, followed by slow resolution of the pigmentation. Compression by the enlarged uterus of peripheral nerves issuing at S1-S2 is proposed as a mechanism of these changes.