--- title: ICD-10-CM Coding for Twin Pregnancy description: When coding for an obstetric patient, the presence of multiple gestation is always coded because it’s a condition that is considered to complicate the pregnancy. image: https://hiacode.com/hubfs/iStock-653859072.jpg --- # ICD-10-CM Coding for Twin Pregnancy ![Cari Greenwood, RHIA, CCS, CPC](https://hiacode.com/hubfs/Cari%20Greenwood%20Author%20Bio%20(1).png) [Cari Greenwood, RHIA, CCS, CPC](https://hiacode.com/blog/author/cari-greenwood) Jan 29, 2025 [Industry News](https://hiacode.com/blog/tag/industry-news) [Medical Coding Tips](https://hiacode.com/blog/tag/medical-coding-tips) ![ICD-10-CM Coding for Twin Pregnancy](https://hiacode.com/hubfs/iStock-653859072.jpg) - Share on: - [![](https://hiacode.com/hubfs/Facebook%20svg.svg)](http://www.facebook.com/share.php?u=https://hiacode.com/blog/coding-for-twin-pregnancy) - [![](https://hiacode.com/hs-fs/hubfs/twitter.png?width=32&height=32&name=twitter.png)](https://twitter.com/intent/tweet?text=I+found+this+interesting+blog+post&url=https://hiacode.com/blog/coding-for-twin-pregnancy) - [![](https://hiacode.com/hubfs/LinkedIn%20svg.svg)](http://www.linkedin.com/shareArticle?mini=true&url=https://hiacode.com/blog/coding-for-twin-pregnancy) - [![](https://hiacode.com/hubfs/mdi_email.svg)](mailto:?subject=Check%20out%20https://hiacode.com/blog/coding-for-twin-pregnancy%20&body=Check%20out%20https://hiacode.com/blog/coding-for-twin-pregnancy&media=https://learn.hiacode.com/hubfs/iStock-653859072.jpg) - ![](https://hiacode.com/hubfs/entypo_link.svg) copied When coding for an obstetric patient, the presence of multiple gestation is always coded because it’s a condition that is considered to complicate the pregnancy. Multiple gestation is reported with an ICD-10-CM code from category **O30 Multiple Gestation**. Codes from this category describe the type of multiple gestation in terms of the **combination of chorions/placenta(s) and amniotic sac(s)** the make up the pregnancy. When describing multiple gestation types, the number of chorions/placentas is referenced first, followed by the number of amniotic sacs. Only twin multiple gestations are covered in this Coding Tip, but the same principles apply to coding for multiple gestations of three or more fetuses. ## Terminology Familiarity with the following terms is essential to understanding the specific placenta/amniotic sac combinations that occur in twin gestations. Chorion – Outer membrane that surrounds the amnion, the fetus and other membranes in the uterus and contributes to the growth of the placenta Amnion – Thin, tough membrane that lines the amniotic cavity and holds the amniotic fluid and developing fetus. ![Amnion Image](https://hiacode.com/hs-fs/hubfs/Amnion%20Image.png?width=550&height=243&name=Amnion%20Image.png) [https://commons.wikimedia.org](https://commons.wikimedia.org) Mo/Mono – One Di – Two Mono/Di chorionic – One/two/three placentas Mono/Di amniotic – One/two/three amniotic sacs ## Types of Twin Pregnancy There are three different types of twin pregnancy. Each type is identified based on the number of chorions/placentas and the number of amniotic sacs that are involved between two fetuses. Dichorionic diamniotic (DiDi) - Two chorions/placentas and two amniotic sacs - Each fetus has its own placenta and its own amniotic sac Monochorionic diamniotic (MoDi) - One chorion/placenta and two amniotic sacs - Both fetuses share one placenta but each has its own amniotic sac Monochorionic monoamniotic (MoMo) - One chorion/placenta and one amniotic sac - Both fetuses share one placenta and one amniotic sac ![Monochorionic monoamniotic (MoMo) Image](https://hiacode.com/hs-fs/hubfs/Monochorionic%20monoamniotic%20(MoMo)%20Image.png?width=649&height=363&name=Monochorionic%20monoamniotic%20(MoMo)%20Image.png) ## ICD-10-CM Coding ICD-10-CM category O30 has codes for reporting any configuration of multiple gestation. Coding for twin pregnancies is the focus of this discussion. Twin pregnancy Subcategory O30.0 includes the codes for pregnancies comprised of two fetuses. Assignment of these codes is pretty straightforward as it follows the terms presented previously. The 5th character of the code indicates the combination of chorions/placentas and amniotic sacs. - O30.0**1**- Monochorionic monoamniotic (MoMo) - This code is assigned if both fetuses share **one placenta** and **one amniotic sac** - O30.0**3**- Monochorionic diamniotic (MoDi) - This code is assigned if both fetuses share **one placenta **but each has its **own amniotic sac** - O30.0**4**- Dichorionic diamniotic (DiDi) - This code is assigned if each fetus has its **own placenta** and its** own amniotic sac** Subcategory O30.0 also includes - O30.00- **Unspecified** number of placenta and unspecified number of amniotic sacs - O30.02- **Conjoined** twin pregnancy - O30.09- **Unable to determine** number of placenta and number of amniotic sacs When selecting among these codes, remember - **“Unspecified”** means the **documentation is incomplete** when specifying the number of placenta and/or amniotic sacs - **“Unable to determine”** means that for some reason the number of placenta and/or amniotic sacs **cannot be counted ** All codes from category O30 require the addition of a **6th character** identifying which **trimester** of pregnancy the patient is in during the encounter being coded. ## Example A 27 yr. old patient is seen at 30 weeks gestation for an OB ultrasound. The findings of the ultrasound show both fetuses having their own amniotic sac but sharing a placenta. ICD-10-CM code: O30.032 Twin pregnancy, monochorionic/diamniotic, second trimester This is a monochorionic pregnancy because there is only one placenta shared between two fetuses and a diamniotic pregnancy because there are two amniotic sacs, one for each fetus. The correct 6th character is “2” because 26 weeks of gestation falls into the second trimester of pregnancy. ## Take Aways - Correct selection of multiple gestation diagnosis codes requires understanding the possible combinations of chorions/placentas and amniotic sacs - Chorions refers to the number of placentas - Amnions refers to the number of amniotic sacs - The possible combinations of twin pregnancies include: - Dichorionic diamniotic (DiDi) - Monochorionic diamniotic (MoDi) - Monochorionic monoamniotic (MoMo) - “Unspecified” means the documentation is incomplete when specifying the number of placenta and/or amniotic sacs - “Unable to determine” means that for some reason the number of placenta and/or amniotic sacs cannot be counted For expanded information on how to code multiple gestation pregnancies, including instruction on how to code for pregnancies with three or more fetuses and additional case studies, see our [eBook ICD-10-CM Coding for Multiple Gestations](https://hiacode.com/resources/multiple-gestation-coding-in-icd-10-cm). [![Multiple Gestation eBook Cover Photo](https://no-cache.hubspot.com/cta/default/20824215/interactive-185525081906.png) ](https://hiacode.com/hs/cta/wi/redirect?encryptedPayload=AVxigLKcMDLEePeDNVM%2FZ1dyB8qFO5rWFFVt%2BzDajF1bmAqWk4%2FTHxD78fMup44Ux6ZnLNQBXqaAOqn%2FxWl%2BStVFzB38P17QiLyYQZWu%2FMlcl5l021jo9AQJB2iG%2BqPGoy4v7KfdR%2BmBLF8uBEGUgHy5la4thS9DmyE6tlCdOYidqbHuwQiiJ7NshqcVsIh8E0OkeSx2jR7M3QdxedhhjHjBb%2BUJbOfw5Rcd&webInteractiveContentId=185525081906&portalId=20824215) **References**  - ICD-10-CM Codebook  - [https://www.multiplesmatter.com/article/types-of-twin-and-triplet-pregnancies](https://www.multiplesmatter.com/article/types-of-twin-and-triplet-pregnancies)  - [https://www.differencebetween.net/science/health/difference-between-amnion-and-chorion/](https://www.differencebetween.net/science/health/difference-between-amnion-and-chorion/)  --- Since 1992, HIA has been the leading provider of [compliance audits](https://hiacode.com/acute-review), [coding support services](https://hiacode.com/acute-coding-support) and [clinical documentation audit services ](https://hiacode.com/clinical-documentation-integrity)for hospitals, [ambulatory surgery centers](https://hiacode.com/asc-coding), physician groups and other healthcare entities. 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