Clinical Questions List
Milk Biomarkers of Secretory Activation in Mothers of Premature Infants

CQ #293 - January 22, 2024

by Anne Eglash MD, IBCLC, FABM

#LactFact

Maternal report of 'milk coming in' is not an accurate measure of onset of secretory activation.

Milk Biomarkers of Secretory Activation in Breast Pump-Dependent Mothers of Preterm Infants: An Integrative Review
Breastfeeding Medicine 19(1) DOI: 10.1089/bfm.2023.0107
What are ways that we can detect the onset of secretory activation (aka when the milk comes in)?

There are many reasons why lactating individuals may have a delay in secretory activation (SA), including high BMI, premature delivery, cesarean birth, stress, breast pump dependency, gestation diabetes, pre-eclampsia, among others. The most common way that researchers have measured the onset of SA is by parental perception, such as breast fullness, change in color of milk, or milk volume.

Why do we need to know about the timing of SA? Knowing whether SA has occurred helps us to understand the possible cause(s) for an individual’s low milk production. For example, when an individual has low production in the second week, it is often unclear if this is due to low glandular tissue or a delay in SA due to medical conditions such as insulin resistance or early postpartum birth control.

Research can help us understand how birth practices and health conditions impact SA, but we need to understand the best way to measure SA.

The study for this week is a review of the different milk biomarkers used to measure SA. The researchers reviewed 40 studies that compared milk biomarkers of SA in pump dependent mothers of preterm infants with healthy term mothers and identified 6 articles that met their criteria for inclusion.

The 4 primary milk biomarkers indicating SA include sodium (Na), lactose, citrate, and total protein. Most studies were small, and the studies collected milk at different time periods and at different frequencies. Some of the studies used 1-2 biomarkers, while others used all 4. Despite the different methodologies, there were some consistent findings. See the question for details!

What do you think are accurate statements about secretory activation (SA) in mothers of premature infants? Choose 1 or more:
  1. Maternal report of ‘milk coming in’ strongly correlates with biomarker measurements of SA.
  2. Mothers of premature infants who ‘come to volume’, meaning express ≥500ml/day by day 14, are more likely to have normal biomarkers of SA much earlier postpartum as compared to those who express <500ml/day by day 14.
  3. Biomarkers of SA are not associated with milk volume.
  4. Increased pump frequency among pump-dependent mothers of premies is strongly associated with earlier SA and coming to volume at 2 weeks postpartum.
  5. A BMI ≥ 27 among pump-dependent mothers of premies has been found to be associated with a slower rate of rise of milk volume in the first few weeks compared to those with a BMI < 27.
  6. Pump-dependent mothers of premies have a higher risk of a delay or impairment of SA.

Click here to view the answer to this question.

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Comments (3)
    Madison Hendry

    Expressing milk within the first hour makes a difference vs expressing after the first hour birth or 6 hrs after birth

    IABLE

    The Parker studies from 2012 and 2015 indicated that expressing milk in the first hour made a difference in milk volume later. However, those were not large enough studies, nor were they randomized controlled trials. They repeated their work in a randomized controlled trial in 2020 and demonstrated that pumping in the first hour is NOT what makes the difference in producing sufficient breast milk. They found that pumping within the first 6 hours was important AND pumping frequently was the key to success. We need to be stressing frequency, and not stressing the importance of pumping in the first hour.
    I have found that people stress that they ‘ruined’ their chances of making enough milk if they don’t pump in the first hour, so it is important to not perpetuate this disproven theory.
    However, I would add that expressing milk in the first few hours for premature infants is important to provide colostrum for oral immune therapy.

    Dorothy Macias

    Thank you for this information. I have seen the challenges that the nurses have when recovering a mom, let’s say with severe PIH,and then needing to start a pump baby going to NICU. I see that it’s a struggle and challenge even after 6 hours have passed to get a pump started. I really have encouraged the nurses to try to teach hand expression prior to delivery so that can be done immediately after delivery. It works for a little while then goes off by the way side. Lactation consultants are way under staffed and at times we don’t get to them until the next day. I do stress the frequency, day and night, and not to skip night time feedings. There has to be a different approach.

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