The following principles were utilized during the 2026 inactivation and remodeling of concepts within the hierarchies 198609003 |Complication of pregnancy, childbirth and/or puerperium (disorder) and 362972006 |Disorder of labor / delivery (disorder).

Temporal Semantics

The modeling of concepts whose FSNs contain certain words have been standardized by a consistent specified temporal value (with occasional exceptions) as tabulated below:

The notion of complication is explicitly stated in legacy material from ICD to refer to ‘adverse evolution’. The existing descendants of |Complication of pregnancy, childbirth AND/OR puerperium (disorder)| were incomplete and predominantly related to maternal disorders but also historically included a small number of fetal concepts affected by the maternal environment. For these reasons, the following concepts have been inactivated as ambiguous with historical association to their respective separate maternal and fetal grouping superordinates:

• 198609003 |Complication of pregnancy, childbirth and/or puerperium (disorder)|

• 609496007 |Complication occurring during pregnancy (disorder)|

• 199745000 |Complication occurring during labor and delivery (disorder)|

Combined high level maternal and fetal grouping concepts, e.g., Maternal disorder and/or fetal disorder during intrapartum period, have not been added, as these coalesced classes can be located using Expression Constraint Language (ECL).

High level general concepts, e.g., 45828008 |Anemia in mother complicating pregnancy, childbirth AND/OR puerperium (disorder), have been inactivated as ambiguous with historical association to an explicit concept relating to the presence of the condition that does not state that it is complicating, for example, |Maternal anemia during antenatal and/or intrapartum and/or postpartum period|.

In contrast, where the word complicating has been applied to a more limited time phase, e.g., 10742121000119104 |Asthma in mother complicating childbirth (disorder), this concept has been retained, as potentially clinically valuable, but marked as incompletely defined (primitive) due to the notion’s inherent lack of specificity. In this exemplar, 10742121000119104 |Asthma in mother complicating childbirth (disorder), could denote the co-occurrence and impact of asthma on labor but the nuance is not explicit, and the notion could also involve the exacerbation of asthma secondary to the process of labor (or, of course, both interactions could be present). Thus, ‘Asthma in mother complicating childbirth’ is semantically more complex than the simple co-occurrence of ‘asthma with childbirth’ and consequently the concept has to be primitive, as the word complicating here captures the ‘adverse evolution’ of certain conditions away from the norm in the intrapartum state.

Concepts such as 34270000 |Miscarriage complicated by shock (disorder) describe the occurrence of shock in the context of a miscarriage, i.e., the shock would not have occurred without the miscarriage; consequently, such concepts have been inactivated and replaced by new concepts, for example, |Shock due to miscarriage|. It is worth noting that no further temporal information is available in the terming as to whether the shock occurred during and/or after the miscarriage.

Concepts with FSNs such as ‘X affecting pregnancy’ and ‘Y affecting management of pregnancy’ have been inactivated and replaced with explicit concepts of the form: |Disorder of pregnancy due to X|

• For example,

  • 443006 |Cystocele affecting pregnancy (disorder) has been inactivated with historical association to a new concept 1381656002 |Maternal cystocele during antenatal and/or intrapartum period (disorder)

  • 106008001 |Delivery AND/OR maternal condition affecting management (disorder) has been inactivated with historical association to 1269075002 |Maternal disorder during intrapartum period (disorder)

The occurrence value for ectopic pregnancy concepts have been defined as Maternal antenatal period with an associated finding site of |Structure of product of conception|. Where the ectopic is explicitly a fetus, this has also been modeled. For example, 237253003 |Viable fetus in abdominal pregnancy (disorder) is modeled as relating to the abdomen within the maternal antenatal period & the fetus in relation to the fetal period, (as, in this case, a viable fetus is a fetal disorder as well as an abdominal pregnancy). The conceptus is an embryo until the end of the eighth week of pregnancy, and from the beginning of the ninth week until delivery, the conceptus is known as the fetus. The first trimester begins at conception until the end of week 12, so this includes the transition between embryo and fetus at the end of 8 weeks gestation.

An ectopic pregnancy is also defined as NOT being within the uterine cavity, but being located in the abdominopelvic cavity or a substructure. Consequently, 198627000 |Angular pregnancy (disorder)|, which is intrauterine, is NOT considered an ectopic pregnancy. Where the site of the ectopic is stated, e.g., 79586000 |Tubal pregnancy (disorder)|, this is modeled with the finding site |Fallopian tube| and an occurrence of |Maternal antenatal period|.

Concepts relating to miscarriage and abortion are both modeled using a finding site of |Structure of product of conception| and an occurrence of |Maternal antenatal period|, e.g., 59363009 |Inevitable abortion (disorder).

The hierarchy 314908006 |Extra-embryonic structure (body structure)| includes:

• 34863009 |Decidua structure (body structure)

• 78067005 |Placental structure (body structure)

• 74439004 |Chorionic structure (body structure)

• 70847004 |Structure of amnion (body structure)

Disorders of extra-embryonic structures excluding the umbilical cord, e.g., placenta, necessarily relate to the Maternal antenatal/intrapartum/postpartum period, as for example, conditions such as ‘uterine retained products of conception’ extend beyond the end of the third stage of labor and persist into the postpartum period. Other disorders, e.g., 36813001 |Placenta previa (disorder)| relate to only the Maternal antenatal and/or intrapartum time period.

Disorders of the umbilical cord necessarily relate to the fetus and/or neonate. Some concepts also relate to the maternal antenatal and intrapartum temporal period, where the pathogenesis of the connecting structure necessarily impacts on the maternal actor, e.g., 270500004 |Prolapsed cord (disorder). Disorders of cord during the postpartum period are modeled with only |Neonatal period|.

The maternal hypertension hierarchy encompasses all concepts representing hypertension present during the antenatal, intrapartum, or postpartum periods. It includes both conditions arising during pregnancy (such as eclampsia) and pre-existing hypertensive conditions.

Legacy concepts and concepts with redundant phrasing have been updated as follows:

• Hypertension in obstetric context: The legacy concept 367390009 |Hypertension in the obstetric context (disorder) has been treated as synonymous with maternal hypertension and inactivated as a duplicate of 288250001 |Maternal hypertension (disorder).

• Chronic hypertension in pregnancy: The legacy phrase chronic hypertension in pregnancy is considered equivalent to pre-existing hypertension. Consequently, 8762007 |Chronic hypertension in obstetric context (disorder)| has been inactivated with historical association to a new concept 1373659007 |Pre-existing hypertension during maternal antenatal and/or intrapartum and/or postpartum period (disorder).

During revisions the working definition used for labor dystocia is: an “abnormal” labor progression during the latent (up to 4-6 cm dilation) or active phase (from 4-6 cm until full dilation) of the first stage of labor; or, during the second stage (from complete cervical dilation until delivery of the baby) - this dystocia can be caused by a variety of etiologies including: uterine, pelvic (passage), and fetal origins. Pre-existing hierarchies for 31805001 |Fetal disproportion (disorder)| and 237256006 |Disorder of pelvic size and disproportion (disorder)| have been harmonized with related clinical findings rationalized to align with the following definitions:

• Fetal orientation: the relationship of the fetus to the uterus, cervix, and maternal pelvis.

• Fetal presentation: the part of the fetus occupying the lower pole of the uterus, or presenting to the pelvic inlet, e.g. vertex (cephalic), face, brow, breech, shoulder, funic (umbilical cord), or compound (more than one part, such as shoulder and hand).

• Fetal position: the relation of the presenting part to an anatomic axis e.g. for vertex presentation this may be occipitoanterior, occipitoposterior or occipitotransverse.

The orientation of a fetus may be determined during the pregnancy by palpation, ultrasound, etc., and these are findings, as the presentation, position, and lie are initially changeable until gradually becoming more set as the pregnancy approaches term. It is at the later stages of pregnancy or during labor that the description of the fetus’ orientation relate to a disorder. This can become confusing ontologically. For example, a transverse lie during pregnancy is not uncommon, and although it may be indicative of an associated condition, e.g., placenta previa, it can be a normal variant. Transverse lie at a later stage of pregnancy, such as in labor, has a more significant nuance, because, not only may it be indicative of various conditions causing difficulty for the fetal head to engage, it can also be associated with an increased incidence of other conditions, such as cord prolapse.

Concepts such as |Isoimmunization affecting pregnancy| have been inactivated as ambiguous with historical association to the maternal disorder of the development of isoimmunization secondary to incompatible (paternally-derived) fetal blood group antigens; and, the hemolytic fetal/neonatal impact:

Maternal isoimmunization has a synonym, Maternal alloimmunization. Although alloimmunization is not strictly synonymous with isoimmunization, the terms are closely related and sometimes used interchangeably in clinical practice. Alloimmunization refers to the immune response generated when an individual is exposed to antigens from another member of the same species (allogeneic), leading to the production of antibodies against these foreign antigens. This process commonly occurs after blood transfusion, organ transplantation, or pregnancy, and can involve a wide range of antigens, including red blood cell (RBC) antigens and human leukocyte antigens (HLA). By contrast, isoimmunization is a subset of alloimmunization, specifically describing the immune response against antigens of the same species that are genetically different but of the same type (isoantigens). In clinical usage, isoimmunization most often refers to maternal sensitization to fetal RBC antigens during pregnancy, such as Rh(D) or other blood group antigens, resulting in hemolytic disease of the fetus or newborn. Thus, alloimmunization is a broader term that encompasses isoimmunization, but in the context of incompatible fetal blood group antigens, alloimmunization and Isoimmunization can be used synonymously.

There has also been considerable discussion as to the meaning of the terms typical, atypical, and irregular in the context of maternal alloimmunization to incompatible fetal blood groups. Following expert consultation the following approach has been implemented:

• typical and regular blood group alloimmunization relates to ABO

• irregular blood group alloimmunization relates to non-ABO blood group antigens

As a consequence of this, concepts relating to atypical blood group antibodies have been inactivated, and a single concept 1381698004 |Maternal irregular blood group isoimmunization during antenatal and/or intrapartum period (disorder)| has been retained.

Where injuries are explicitly traumatic and associated with the antenatal or intrapartum period, these are modeled in harmony with other domains using ‘Due to: Traumatic event’.

Concepts with FSNs containing the notion of damage, e.g., 1269255003 |Damage to organ of pelvis due to incomplete miscarriage (disorder)| have been modeled as subtypes of 417163006 |Traumatic or non-traumatic injury (disorder)|. Similarly, for more specific morphologies such as perforation where the etiology is also not necessarily due to a traumatic event, e.g.. 8071005 |Miscarriage with perforation of bowel (disorder), these concepts are also classified as subtypes of 417163006 |Traumatic or non-traumatic injury (disorder)|. By contrast, other specific morphologies, including laceration, e.g., 7809009 |Miscarriage with laceration of uterus (disorder)|, are necessarily traumatic and are modeled with ‘Due to: Traumatic event’.

Concepts temporally relating to trauma and a procedure, e.g., 56451001 |Failed attempted abortion with perforation of broad ligament (disorder)|, are modeled as being ‘Due to: Traumatic event’ and ‘During: Termination of pregnancy (procedure)’.

Where an injury relates to a concept which explicitly states the form of delivery, this has been included in the definition, e.g., 1354495004 |Injury of urethra during vaginal delivery (disorder)| is modeled with ‘Due to: Traumatic event’ and ‘During: 700000006 |Vaginal delivery of fetus (procedure)|’.

Pregnancy Periods

The life phase of pregnancy is unique in that two actors are participants in the scenario, and modeling must distinguish between the two.

• For example,

  • Fetal tachycardia in antepartum versus Maternal tachycardia in antepartum

Mother and fetus share many time periods, such as antenatal. However, some periods are not shared, as in the case of intrapartum. The mother’s intrapartum period includes stages one, two, and three; the fetus’ intrapartum period includes only stages one and two.

A diagram of the relationships between these periods is shown below:

The life phase of pregnancy-related findings and disorders is applied using the Occurrence (attribute). A concept must identify:

1. Which actor (mother or the fetus/neonate) does the circumstance relate

2. In which life phase of the actor does the condition necessarily relate

In the majority of circumstances, the actor to which the condition relates is straight forward: mother or fetus or neonate.

For example,

• Antenatal care relates to both the mother and fetus/neonate

• Antenatal depression clearly relates to the mother

• Short cord with antenatal problem directly relates to the fetus

Other instances such as Intrapartum hemorrhage due to marginal placenta previa may not be so clear without explicit modeling, as hemorrhage with placenta previa can relate to the fetus or mother.

The word perinatal within finding terms is problematic, because it almost always relates to the fetus/neonate. Due vigilance is required to exclude the rare possibility that the condition could relate to the mother. Perinatal can refer to the mother alone (perinatal depression) or to a time period relating to the fetus until the neonate is seven days old.

This situation creates two problems:

#1

The term perinatal is a term with widely varying definitions across countries due in part to legal variations in the time period that defines stillbirth.

The term neonatal generally describes an infant within the first 28 days. Where the condition relates to an infant within the first seven days, the term early neonatal is allocated. The term late neonatal is used from day eight to 28 (WHO, 1992). Although these descriptions are used widely, they are not universally accepted worldwide. These time periods are useful, however, in modeling existing content which was derived from WHO sources.

Future content should use the term neonatal unless a valid use case can be supported in the content request to distinguish between the early and late neonatal period.

#2

The terming of the perinatal period for the fetus and neonate is problematic as there is not a clinically useful name for the actor that covers this entire temporal period. It is possible that baby might be applicable, i.e., Perinatal disorder of baby , but this is not used clinically. To create an explicit FSN, the rather ungainly term |[Clinical finding] of fetus and/or early neonate| has been used. This problem is anticipated to be temporary, as new content will be steered to explicitly state whether the condition relates to the fetus or to the neonate.

In relation to the neonate, there is a clinical and epidemiological distinction between the early neonatal period and the late neonatal period. Conditions in the immediate (early) neonatal period are largely influenced by intrauterine conditions; those in the late neonatal period are more influenced by early extrauterine life. This distinction is important as perinatal disorders historically were often considered a concatenation of disorders occurring in the fetal phase and the early neonatal phase. However, one unresolvable difficulty with this definition is that there is no international agreement in the definition of perinatal phase , which has variable definitions:

• WHO = 22 completed weeks of gestation and ends seven completed days after birth

• UK = the time from fetal viability from about 24 weeks of pregnancy up to seven days of life

• USA = 28 weeks of gestation to the end of the seventh day of life

• Australia = 20 completed weeks of gestation and ends 28 completed days after birth

Maternal time period values can be found in the subhierarchies below:

Generally, it is clear what the appropriate value is, but some knowledge is required to distinguish the correct choice in some circumstances. Definitions have been added to aid in correct selection.

For example,

In relation to postpartum uterine hemorrhage , this would be modeled using an Occurrence (attribute) of Postpartum period. The puerperium is generally defined as the period within 42 days after birth, and thus, the postpartum period relates to this six-week timeframe. Some conditions can occur more than 6 weeks post-delivery, e.g., postpartum thyroiditis , postnatal depression (onset can range from a few days to a few weeks following delivery, generally in the first 2–3 months following childbirth). In this situation, the choice of the more general Maternal postnatal period should be made.

Similar to the Maternal time periods above, the fetal period is the superordinate as illustrated below. There is no label for the concatenated time of the actor during the fetal and neonatal period within medicine (though colloquially called baby), and so the superordinate is named fetal and/or neonate. Similarly, to find concepts which describe conditions of this global phase requires a preferred term expressing this, but in the case of perinatal conditions relating to the fetus and/or early neonate, the word perinatal is commonly used as a substitute.

Review is ongoing of all disorder concepts containing the phrase fetal or neonatal. The concept 450426006 |Fetal or neonatal period (qualifier value)| will be inactivated, leaving only 1156676003 |Fetal and/or neonatal period (qualifier value)|.

• The fetal or neonatal value is historically derived from ICD and may contain legacy context causing ambiguity.

• The fetal and/or neonatal period is explicitly designed to subsume the fetal period, the neonatal period , and in rare cases where these two may overlap, as in 1193538001 |Fetal intrapartum second stage and/or early neonatal period (qualifier value).

Model as IS A 362972006 | Disorder of labor / delivery (disorder)| due to X (disorder).

The definition status of the concept 87476004 |Neonatal seizure (finding)| is to remain primitive for two reasons:

• The time period where a neonatal seizure may occur (from birth to 44 weeks postmenstrual age) differs from the period usually representing the neonatal phase of life (the first 28 days following birth).

• Defining this concept results in incorrect subsumption with types of epilepsy being classified as subtypes. Epilepsy is not a type of seizure, rather an epileptic seizure is a manifestation of epilepsy.