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.

PERINATAL & NEONATAL

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

Pregnancy Period Values

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.

Fetal Neonatal Period Values

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.

Fetal and/or neonatal period versus Fetal or neonatal period

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).