--- O30.001 Twin pregnancy, unspecified number of placenta and unspecified number of amniotic sacs, first trimester

--- O30.002 Twin pregnancy, unspecified number of placenta and unspecified number of amniotic sacs, second trimester

--- O30.003 Twin pregnancy, unspecified number of placenta and unspecified number of amniotic sacs, third trimester

--- O30.009 Twin pregnancy, unspecified number of placenta and unspecified number of amniotic sacs, unspecified trimester