Korea JKMS Birth-Weight Reference, 2016

When

The Korean birth-weight reference was published in 2016 in the Journal of Korean Medical Science.

Who Developed It

The study was conducted by Korean researchers using Korean Statistical Information Service birth data. The article lists Jae Kwan Lee, Hyun-Lim Jang, Bo Hye Kang, Kyung-Sook Shim, Yun Sil Chang, Chong-Woo Bae, and So-Hee Chung among the authors.

Source: https://jkms.org/DOIx.php?id=10.3346%2Fjkms.2016.31.6.939

Why This Source Is Credible

This source is credible because it was published in a peer-reviewed medical journal and used a very large national Korean birth dataset. The study describes its inclusion and exclusion criteria, gestational-age range, sex and plurality handling, and statistical method for addressing known error patterns in administrative data.

Its credibility is strongest as a Korean population birth-weight reference because it is based on more than 1.4 million births after exclusions.

Who Was Included

The study used Korean Statistical Information Service data for all newborns from January 2010 through December 2012.

The raw dataset included 1,425,986 newborns. After excluding records with unknown birth weight, unknown gestational age, gestational age below 22 weeks, or gestational age above 42 weeks, the study analyzed 1,422,890 births.

The reference considered:

• gestational age
• birth weight
• newborn sex
• plurality, including singleton and multiple births

Measurement Type

This source is based on measured birth weight after delivery, not antenatal ultrasound estimated fetal weight. Birth weight is a direct post-delivery measurement, while estimated fetal weight is a prenatal calculation from ultrasound measurements.

This difference is important because a birth-weight percentile and an ultrasound estimated fetal weight percentile are related comparisons, but they are not the same type of measurement.

How It Was Built

The study analyzed birth weight by completed gestational week. Gestational age was defined as the interval between the first day of the mother's last menstrual period and the delivery date, expressed in completed weeks. Birth weight was measured to the nearest 10 grams.

The authors identified error patterns in the large national dataset, including a double-humped distribution around 28 to 32 weeks. They used a finite Gaussian mixture model to remove estimated error data before building the percentile distributions.

What It Means

This source shows Korean newborn birth-weight percentiles by gestational age, sex, and plurality. It is a birth-weight reference, not an antenatal ultrasound estimated fetal weight reference.

This distinction matters. Birth weight is measured after delivery. Estimated fetal weight is calculated before delivery from ultrasound measurements. They are related but not identical.

How To Interpret It

Use this source as a Korean population birth-weight comparison. It can help show how a weight value compares with Korean newborn birth-weight distributions at the same completed gestational week.

When comparing an ultrasound estimated fetal weight with this source, interpret the result cautiously. The comparison is between a prenatal estimate and a birth-weight distribution, not between two identical measurement types.

What This Source Should Not Be Used For

This source should not be used by itself to diagnose fetal growth restriction, macrosomia, placental insufficiency, or pregnancy risk. It should not be treated as an ultrasound fetal growth standard because it is based on birth weights after delivery. Clinical interpretation requires pregnancy context, timing of delivery, gestational dating, and clinician assessment.

Limitations

• This is a birth-weight dataset, not an ultrasound EFW dataset.
• Birth-weight distributions can be affected by which pregnancies deliver at each gestational week.
• Preterm births may reflect medical conditions that caused earlier delivery, so they may not represent all ongoing pregnancies at that same gestational age.
• The source is specific to Korea and may not apply to other populations.
• Large administrative datasets can contain reporting errors; the authors addressed known error patterns statistically, but this remains an important context.
• A percentile comparison does not diagnose fetal growth restriction, macrosomia, or pregnancy complications.

Bottom Line

The Korea JKMS 2016 reference is valuable because it is based on a very large national Korean birth dataset and separates results by gestational age, sex, and plurality. Its main limitation is that it is based on birth weight, so it must be interpreted differently from ultrasound estimated fetal weight references.