Growth Calculator

  • We calculate 4 data points for this calculator. Total gain, Average gain per week, Male percentile, Female percentile.
  • We also calculate between Weeks and Months with a rate of: 1 Month = 4.345 Weeks. This follows from 365 / 7 = 52.143 and 52.143 / 12 = 4.345. 

Total gain:  Current Weight – Birth Weight

Average gain per week: Total Gain / Weeks

(Note this method does not account for growth velocity changes over time, it is an average. We would need to collect one more weight sample near the Current Weight sample to accurately compute Velocity. We are thinking about building this as an additional tool because we would then be able to give percentiles compared to WHO Growth Velocity data.)

Male and Female Percentiles:

  • These are based on WHO Child Growth standards, using the birth to 24 months data found here: https://www.who.int/tools/child-growth-standards/standards/weight-for-age
  • We are using the LMS Method for determining percentiles, by using the LMS values published by the WHO in their data charts provided in the link above.
  • Additionally when an age falls between months (ex: Age = 1.7 Months), we are computing a blended set of LMS values by finding the value between the two months. In the example of 1.7 Months, we would use the values that are 70% of the way between the 1 Month values and 2 Month values. This technique yields percentiles that are accurate (as compared with WHO week-based data) within 2%. The slight discrepancy here is caused by the non-uniform distribution of weight changes within the course of a month. A future improvement will be to use the week-based data for ages less than 13 weeks (the limit of this data) and use month-based data for ages from 13 weeks until 24 months.
  • We do not support percentiles for ages over 24 months.

 

Feeding Calculator

  • This calculator is broken into the two high-level groups we need to support: Ages < 1 week and Ages >= 1 week.

For Ages < 1 week:

We base this calculation on the Academy of Breastfeeding Medicine’s Clinical Protocol #3.

    • The guidance given in this protocol is only at the “per feeding” granularity and has a wide range. For example, 2-10 mL/feed in the first 24 hours.
    • Since our goal is to allow users of our calculator to pick the intended number of feedings, we are using this protocol’s data with an understanding that the low end of the range is correlated to a higher number of daily feeds and the high end of the range is correlated to a lower number of feeds. With this understanding we calculate smaller ranges based on the desired number of feedings. The result is provided in milliliters and  liquid ounces.

For Ages >= 1 week:

We base this calculation on 2023 Meta-Analysis by Rios-Leyvraz and Yao, published in Breastfeeding Medicine Volume 18, Number 3. Specifically Table 3. “Mean Breast Milk Intake” 

  • This table gives us the mean intake value of mL/kg per day, based on age in months. The table also provides a small range representing one standard deviation from the mean which we use to calculate the low and high points of our range.
  • Given this data we collect the age of the baby and the current weight to determine the daily average intake, and then allow users to choose the desired number of feedings per day to determine the per feeding volumes.
  • We provide the low and high points of the range corresponding to one standard deviation as given in the data, and we provide the data in both fluid ounces and milliliters.

Triple Feeding Calculator

This calculator uses the same methodology as the “Ages 1 week to 1 month” group from the Feeding Calculator to determine the average total amount of intake. 

  • We divide the number of feedings per day to determine the per feeding target amount.
  • Then we subtract the amount of transfer observed in a single feeding, to determine the amount of supplementation needed per feeding.
  • We output the total amount per feeding and the supplementation amount per feeding in both liquid ounces and milliliters.

References

Kellams, A., Harrel, C., Omage, S., Gregory, C., Rosen-Carole, C., & the Academy of Breastfeeding Medicine. (2017). ABM clinical protocol #3: Supplementary feedings in the healthy term breastfed neonate, revised 2017. Breastfeeding Medicine, 12(3), 1–11. https://doi.org/10.1089/bfm.2017.29038.ajk

Rios-Leyvraz, M., & Yao, Q. (2023). The volume of breast milk intake in infants and young children: A systematic review and meta-analysis. Breastfeeding Medicine, 18(3), 188–197. https://doi.org/10.1089/bfm.2022.0281