Mexico's supreme court on Wednesday let stand a right-to-life amendment to the Baja California state constitution that says life begins at conception and effectively bans elective abortions in the northern border state.

The ruling appeared to allow Mexican states to decide individually on the abortion question, though the court has also agreed to review a similar amendment from the north-central state of San Luis Potosi.

Sixteen of Mexico's 31 states have adopted right-to-life amendments that severely restrict abortions, though almost all continue to allow it under some circumstances like rape or danger to a mother's life. Only Mexico City has legalized abortion on demand in the first trimester.

Seven justices of the 11-member court voted to overturn the amendment, arguing it was a federal issue, or could violate federally guaranteed rights. But eight votes are needed to overturn a law on grounds of unconstitutionality