What does this LOINC code represent?

This LOINC code identifies a lab observation, measurement, question, or clinical concept in a standardized format.

Is this enough to understand my test result?

No. The code identifies the test or observation, but the interpretation depends on the actual result, reference range, and clinical context.

LOINCActiveObservation

LOINC Code 33198-3: Fetal Head Diameter.biparietal estimated from gestational age by method of Hadlock 1984 (US)

Name: LOINC Code 33198-3: Fetal Head Diameter.biparietal estimated from gestational age by method of Hadlock 1984 (US)
Creator: HealthAssure Clinical Team
Published: 2026-05-21T08:59:20.067Z

33198-3 is a LOINC code used to identify Fetal Head Diameter.biparietal estimated from gestational age by method of Hadlock 1984 (US) in laboratory and clinical observation data. You may see this code in lab systems, lab reports, EHR exports, interoperability feeds, or other structured clinical data exchanges. LOINC codes identify tests, measurements, observations, survey items, and clinical questions in a standardized way. It is associated with the component Diameter.biparietal. It is commonly used with the system or sample type Head^Fetus.

Reviewed by HealthAssure Clinical TeamUpdated 21 May 2026

What is this code?

LOINC codes identify tests, measurements, observations, survey items, and clinical questions in a standardized way. It is associated with the component Diameter.biparietal. It is commonly used with the system or sample type Head^Fetus.

When is it used?

Used in lab systems, EHRs, and clinical data exchange.
May identify a test, observation, survey item, or clinical document request rather than a diagnosis.
Status: ACTIVE
Order vs observation: Observation
Method: US.estimated from Hadlock 1984

What it does not mean

The code identifies the observation or test, not the actual result.

Key facts

Fetal Head Diameter.biparietal estimated from gestational age by method of Hadlock 1984 (US)
Diameter.biparietal
84; BPD; BPD by GA; BPD predicted from gestational age; Brain; Cranial; Cranium; DIA; Diam; Echoencephalogram; Echoencephalography; Echography; Est; estimation; Fetal; from GA.Hadlock 1984; Gyn; Gynecology; Intracranial; Length; OB; ObGyn; OBSTERICAL; OBSTERICAL.ULTRASOUND; Obstetrical; Obstetrics; Point in time; predicted; QNT; Quan; Quant; Quantitative; Random; Skull; Sonogram; Sonograph; Sonography; ULS; Ultrasound; US+est

Where you may see this code

You may see this code in lab systems, lab reports, EHR exports, interoperability feeds, or other structured clinical data exchanges.

Common synonyms

Fetal Head Diameter.biparietal estimated from gestational age by method of Hadlock 1984 (US)Fet BPD from GA.Hadlock 1984Diameter.biparietalOB.USLenPtHead^fetus

Frequently asked questions

Code details

Code33198-3

SystemLOINC

Display nameFetal Head Diameter.biparietal estimated from gestational age by method of Hadlock 1984 (US)

DescriptionDiameter.biparietal

Short nameFet BPD from GA.Hadlock 1984

ComponentDiameter.biparietal

PropertyLen

TimingPt

System (specimen)Head^Fetus

ScaleQn

MethodUS.estimated from Hadlock 1984

ClassOB.US

Example unitsmm

StatusACTIVE

Order/ObservationObservation

Flags

BillableNo

Valid clinical useNo

Source

SourceLOINC

Version2.82

Releasemain

First released2.09

Last changed2.70

Part names

Diameter.biparietalLenPtHead^fetusQnUS.estimated from Hadlock 1984LengthPoint in time (spot)Ultrasound.estimated from Hadlock 1984

About this content

This page is prepared by HealthAssure's clinical team using official coding standards from LOINC. AI tools assist with drafting explanations, which are then reviewed and verified by healthcare professionals for accuracy. This content is for informational purposes and does not replace professional medical advice. Meet our team.