ICD-10-CM > O00-O9A > O20-O29 > O26 > O26.1 O26.1 Low weight gain in pregnancy Non-Billable/Non-Specific Codes O26.10Low weight gain in pregnancy, unspecified trimesterO26.11Low weight gain in pregnancy, first trimesterO26.12Low weight gain in pregnancy, second trimesterO26.13Low weight gain in pregnancy, third trimester