Association between maternal stress and premature milk cortisol, milk IgA, and infant health: a cohort study

Background

Maternal stress is pervasive in the neonatal intensive care unit (NICU). Maternal stress is associated with changes in human milk (HM) immunomodulatory agents, which may impact neonatal health. We sought to determine the association between maternal stress, HM immunoglobulin A (IgA) and cortisol, and to assess how these milk components correlate with infant immune and neurodevelopmental outcomes. We then compared how these associations persist over time.

Methods

The study design involved a cohort study of exclusively breastfeeding mothers and their singleton moderately preterm (28-34 weeks) infants admitted to the NICU. We collected maternal serum, maternal saliva, and first-morning whole milk samples, and administered maternal stress questionnaires at 1 and 5 weeks postpartum. We analyzed the samples for HM IgA (using a customized immunoassay in skim milk) and for HM and salivary cortisol (using a chemiluminescent immunoassay). Infant illness was assessed using the Score for Neonatal Acute Physiology II (SNAP II) and SNAP II with Perinatal Extension (SNAPPE II), and infant neurodevelopment were assessed using the Test of Infant Motor Performance. We analyzed changes in HM IgA and cortisol over time using paired t-tests. Furthermore, we performed correlation and regression analyses after adjusting for gestational age (GA), corrected GA, and infant days of life.

Results

In our study, we enrolled 26 dyads, with a mean maternal age of 28.1 years, consisting of 69% white, 19% Black, and 8% Hispanic. Cortisol: Salivary and HM cortisol were closely associated in week 1 but not in week 5. Though mean salivary cortisol remained stable over time [2.41 ng/mL (SD 2.43) to 2.32 (SD 1.77), p = 0.17], mean HM cortisol increased [1.96 ng/mL (SD 1.93) to 5.93 ng/mL (SD 3.83), p < 0.001]. Stress measures were inversely associated with HM cortisol at week 1 but not at week 5. IgA: HM IgA decreased over time (mean = -0.14 mg/mL, SD 0.53, p < 0.0001). High maternal stress, as measured by the Parental Stressor Scale: neonatal intensive care unit (PSS:NICU), was positively associated with HM IgA at week 5 (r = 0.79, P ≤ 0.001). Higher IgA was associated with a lower (better) SNAP II score at week 1 (r = -0.74, p = 0.05). No associations were found between maternal stress, salivary cortisol, HM cortisol, or HM IgA and neurodevelopment at discharge (as assessed using the TIMP score). Furthermore, these relationships did not differ by infant sex.

Conclusion

Maternal stress showed associations with HM cortisol and HM IgA. In turn, HM IgA was associated with lower measures of infant illness.

Does Human Milk Insulin Help Program Infant Pancreatic Function? Variation in Neonatal Human Milk Insulin Is Associated with Later Measures of Infant Glycemic Control

Objectives

Whether variation in human milk (HM) insulin contributes to neonatal blood sugar regulation and pancreatic programming remains unknown. This pilot study investigates whether HM insulin concentrations correlate with infant pancreatic function in exclusively breastfed 5-month old infants. We hypothesize that neonatal exposure to elevated HM insulin will “under stimulate” the infant pancreas, resulting in an exaggerated glycemic response to oral glucose at 5 months.

Methods

Exclusively breastfed infants of normoglycemic mothers (NG; n = 5) and mothers with minor insulin resistance (IR; n = 5) were administered a 1.75 g/kg oral glucose challenge. Infant capillary glucose was assessed at Fasting (&gt;2 hours), 30 minutes (T30) and 60 minute (T60) after glucose administration. Fasting HM insulin was measured at 2-weeks and 5-months. Repeated Measures ANOVA and linear regression analyses were utilized.

Results

Using repeated measures analysis, the IR group exhibited a more dramatic glycemic response to the glucose challenge (P = 0.031): exhibiting lower fasting glucose (P = 0.085; n = 10) and higher glucose excursion from fasting to T30 (P = 0.007) compared to the NG group. HM insulin did not differ between the NW and IR groups at 2-weeks or 5-months. However, higher HM insulin concentrations at 2-weeks did correlate with a more dramatic infant glycemic response to oral glucose at 5 months. Fasting HM insulin at 2 weeks was positively associated with infant glucose at T30 (P = 0.033) and with the increase in glucose from fasting to T30 (P = 0.081; n = 8). Furthermore, fasting HM insulin at 2-weeks was negatively associated with infant glucose at T60 (P = 0.031) and the change in glucose from T30-T60 (P = 0.032; n = 7).

Conclusions

These pilot results suggest that HM insulin may contribute to postnatal programming of infant pancreatic function such that chronic exposure to elevated HM insulin may result in a dampened pancreatic response to an oral glucose challenge. Confirmation in a larger sample size is necessary.

Funding Sources

NIH/NIDDK; The Gerber Foundation.

The effect of long standing chronic mechanical irritation on the tongue of rats

The effect of long standing mechanical irritation of the tongue was studied in 100 young rats. This was effected by the protruding end of a twisted wire, ligated around the lower first molar and directed toward the later-ventral aspect of the tongue on one side, while the other side served as control. Groups of rats were killed after 3, 6, 9 and 12 months and the tongues were examined grossly and microscopically. Fibrous hyperplasia was observed in 48% of tongues in the 3-month group and increased to 79% in the 12-month group. Microscopically, epithelial changes were noted which included ulceration acanthosis and hyperkeratosis. In no instance was dyskeratosis or any other malignant change noted.