ICD-10-CM > O00-O9A > O30-O48 > O30 > O30.0 > O30.01 O30.01 Twin pregnancy, monochorionic/monoamniotic Non-Billable/Non-Specific Applicable To Twin pregnancy, one placenta, one amniotic sac Type 1 Excludes conjoined twins (O30.02-) Codes O30.011Twin pregnancy, monochorionic/monoamniotic, first trimesterO30.012Twin pregnancy, monochorionic/monoamniotic, second trimesterO30.013Twin pregnancy, monochorionic/monoamniotic, third trimesterO30.019Twin pregnancy, monochorionic/monoamniotic, unspecified trimester