HLA-G, a non-classical class I gene, is located within the human major histocompatibility complex locus. It has a tissue-specific expression in trophoblast, where the products of HLA-A, -B and -C classical genes are absent. Therefore, the HLA-G gene may have a role during pregnancy in inducing protection of the semi-allogeneic fetus from recognition and destruction by maternal immune cells. The primary transcript of the HLA-G gene is alternatively spliced into 6 mRNA forms (HLA-G1 to HLA-G6), 2 of them may encode soluble forms of the HLA-G antigen (HLA-G5 and HLA-G6). In this work, by using reverse transcription polymerase chain reaction technique, we demonstrate that all transcripts are detected in similar amounts, both in the first and third trimester of gestation. These results are discussed in context of putative function of HLA-G antigen isoforms.