How Do I Calculate Mid-Parental Height and Other Growth Parameters?

Patient Presentation
A 5-year-old male came to clinic for his health supervision visit. His father was concerned because he seemed “short” to him and wanted to know how tall he would be when he grew up. Otherwise there were no concerns. His father was 5 foot 9 inches and his mother was 5 foot 3 inches tall. His father said that both parents went through puberty “at the normal times.” The boys’ growth chart showed him to be growing at the 10-25% for height and 50% for weight. The family history showed diabetes and stroke.

The pertinent physical exam showed a happy boy with a weight of 18 kg (50th %) and height of 106 cm (25%) and a BMI of 16 (50%). He was Tanner stage 1 and had a normal examination. The diagnosis of a healthy normally growing boy was made. The resident seeing him knew there was a calculation for evaluating mid-parental height but didn’t know what it was. When she talked with the attending physician they reviewed the calculation and determined that his midparental height would be [paternal height of 69 inches + (maternal height of 63 inches + 5 inches or 68 inches )] / 2 or 68.5 inches. This calculated height also appeared to be consistent with his previous and current growth pattern and was communicated to the family.

Discussion
Parents and pediatric healthcare providers are very concerned with children’s growth as it is such an important marker of their health status. Healthcare providers know, but parents often need to be educated, that it is not the exact measurements but the change in height, weight or head circumference that is the most important determinant. Therefore knowing some basic growth parameters and their changes over time are extremely important for analyzing children’s growth patterns. Children that appear to not be following these general patterns may do so for many reasons such as prematurity, chronic illness, or genetic constitution. But children who are not following these general patterns need to be at a minimum monitored closely and an appropriate evaluation begun if they appear to continue to be deviating from the normal patterns or if the deviation is increasing.

Learning Point
Averages at Birth
Weight = 3.5 kg (7.7 pounds)
Head circumference = 35 cm (14 inches)
Length = 50 cm (20 inches)

Weight
Infant weight gain averages 30 grams/day for the first 3 months, then decreases to 10-20 grams/day for the first year
Infants double their birth weight by 6 months and triple by 12 month of age
Estimated Weight: [2 x(age in years)] + 10 = weight in kg
General averages of weight at:

    1 year = 10 kg (22 pounds)
    5 years = 20 kg (44 pounds)
    10 years = 30 kg (66 pounds)
    11-12 years = 36 kg (80 pounds to be able to move out of a car booster seat)

Underweight
Age <3 years = weight for length is <3rd percentile for age
Or
Age >2 years = BMI for age is <5th percentile for age

Overweight
Age 95th percentile for age
Or
Age >2 years = BMI for age is >95th percentile for age or BMI is >30 kg/m2

Height
General averages of height increase are:

    0-1 year = 10 inches/year (25 cm/year)
    1-2 years = 5 inches/year (12.5 cm/year)
    2 year-puberty = 2.5 inches/year (6.25 cm/year)

Calculation of Mid-Parental Height
This calculation corrects for the opposite gender parents height so that a mid-parental height can be calculated and evaluated on the appropriate gender growth chart
For boys: [paternal height + (maternal height + 5 inches or 13 centimeters)] / 2
For girls: [maternal height + (paternal height – 5 inches or 13 centimeters)] / 2

Head Circumference
General averages for head circumference increase are:

    0-3 months = 2 cm/month (average 3 month old is 41 cm)
    0-1 year = 1 cm/month (average 1 year old is 47 cm)
    > 1 year = only another 8 cm total (average adult is 55 cm)

Premature Infants
When evaluating growth in premature children, they should have prematurity corrected for until 2.5 years of age chronologically.
Some children may “catch-up” before this depending on many factors.

Questions for Further Discussion
1. How much weight and height should a normal school age child gain in a year?
2. At 2 years old, how can you tell what the high school graduation cap size will be?
3. What are the indications for an endocrinology evaluation for a child with abnormal growth patterns?
4. Explain the differences between constitutional growth delay and familial short stature?
5. Where can I find normal growth parameters for common genetic syndromes or non-U.S. populations?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at SearchingPediatrics.com, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for these topics: Child Development and Growth Disorders.

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

Bacon GE, Spencer ML, Hopwood NJ, Kelch RP. A Practical Approach to Pediatric Endocrinology. Year Book Medical Publisher, Chicago, IL. 1990;62-96.

Grover G. Nutritional Needs in Pediatrics a Primary Care Approach, Berkowitz CD, ed. W.B. Saunders Co., Philadelphia, PA. 1996;35-36.

Custer JW, Rau RE. The Harriet Lane Handbook. 18th. Edit. Elsevier/Mosby Publications: Philadelphia, PA. 2009:285, 561-576.

ACGME Competencies Highlighted by Case

  • Patient Care
    1. When interacting with patients and their families, the health care professional communicates effectively and demonstrates caring and respectful behaviors.
    2. Essential and accurate information about the patients’ is gathered.
    3. Informed decisions about diagnostic and therapeutic interventions based on patient information and preferences, up-to-date scientific evidence, and clinical judgment is made.
    5. Patients and their families are counseled and educated.
    8. Health care services aimed at preventing health problems or maintaining health are provided.

  • Medical Knowledge
    10. An investigatory and analytic thinking approach to the clinical situation is demonstrated.
    11. Basic and clinically supportive sciences appropriate to their discipline are known and applied.

  • Practice Based Learning and Improvement
    13. Information about other populations of patients, especially the larger population from which this patient is drawn, is obtained and used.
    15. Information technology to manage information, access on-line medical information and support the healthcare professional’s own education is used.
    16. Learning of students and other health care professionals is facilitated.

    Author
    Donna M. D’Alessandro, MD
    Professor of Pediatrics, University of Iowa Children’s Hospital