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Optimal Oral Feeding Time Analysis

Relationship between post-menstrual age (PMA) at first oral feeding and time to full oral feeding (FOF) in preterm infants (<32 weeks gestation).

Summary

228 preterm infants (<32w gestation), 18 analyses, three research questions.

  • RQ1 (predictors): GA, birth weight, respiratory status — clear associations
  • RQ2 (PMA→FOF relationship): differs before/after 35w PMA (interaction p=0.032 unadjusted, 0.052 adjusted), but absolute outcomes are similar between groups
  • RQ3 (optimal timing): no universal optimal identified
  • Within the O2 subset specifically, timing has no association with outcome (r=0.05)
  • Timing alone explains <7% of variance; with covariates ~15%
  • Data do not support specific timing protocols

RQ1: What predicts when feeding starts?

(Report 6a)

Predictor Result p-value
Gestational age r = -0.259 <0.0001
Birth weight r = -0.349 <0.0001
Mechanical ventilation 1.0 week later (F=26.97) <0.0001
O2 at 36 weeks 0.9 week later (F=15.58) 0.0001

Lower GA, lower birth weight, and respiratory morbidity are each associated with later PMA at first feeding.

RQ2: Does PMA at first feeding relate to time to FOF?

Report 18 regresses continuous PMA at first feeding on time to FOF, stratified by the 35-week threshold. 166 infants (72.8%) started before 35w PMA; 62 (27.2%) at or after.

Group Adjusted Slope p
<35w (n=166) -3.275 0.009
>=35w (n=62) -0.200 0.901
Interaction 0.052

The slopes have opposite directions. Among <35w starters, later PMA at first feeding is associated with shorter time to FOF. Among >=35w starters, no relationship. The interaction is significant unadjusted (p=0.032) but borderline after adjusting for GA, birth weight, mechanical ventilation, and O2 at 36 weeks (p=0.052).

Despite different slopes, absolute time to FOF is similar: 15.6 vs 16.5 days (p=0.638, d=-0.07) per Report 15. Which infants start late is non-random — late feeders are more premature (p=0.023), lower birth weight (p=0.0002), and more likely to have had mechanical ventilation (p<0.0001).

Reports 10/11 show the same interaction using PMA at full feed as outcome (slopes 0.66 vs 1.23, same p-values).

RQ3: Is there an optimal time to start feeding?

Report 13 stratified the full cohort by O2 status and found distinct patterns: the non-O2 group (n≈168) shows timing-dependent patterns (though statistically fragile), while the O2 group (n≈60) shows covariate-dependent patterns with no timing signal.

Report 17 examines feeding timing within the O2 subset specifically. Among the 60 infants requiring O2 at 36 weeks, early vs late feeders (split at median 57.6 days) show no difference in time to FOF: 19.1 vs 22.2 days (p=0.36, d=-0.24). Correlation between feeding start time and time to FOF is essentially zero (r=0.05, R²=0.003). No optimal timing was identified via quadratic modeling.

Across all models, timing alone explains <7% of outcome variance. With covariates, ~15%. 85%+ remains unexplained.

Study Population

Inclusion Criteria

  • Infants born <32 weeks gestation
  • Discharged from the hospital fully orally feeding
  • Started orally feeding before 40 weeks PMA

Exclusion Criteria

  • Infants discharged with tube feeding (NG or GT)
  • Transferred to outside hospital before achieving full oral feeding
  • Transferred in from another hospital after starting oral feeding
  • Died during NICU admission
  • Same-day discharge as last tube feed

Sample Characteristics

  • Final sample: 228 infants (after exclusions)
  • Exclusions: 45 infants (16.5%) due to same-day discharge criteria

Key Variables

Infant Characteristics (Predictors)

Continuous Variables:

  • gestational_age_weeks - Gestational age in weeks (<32 weeks inclusion)
  • birth_weight_grams - Birth weight in grams

Categorical Variables:

  • medicalcomplexity - Pediatric Medical Complexity Algorithm (0-2 scale)
    • 0 = Children without chronic disease
    • 1 = Children with noncomplex chronic disease
    • 2 = Children with complex chronic disease
  • baby_sex - Male/Female
  • race_ethnicity - Combined race/ethnicity variable
  • mechanical_ventilation - History of mechanical ventilation (yes/no)
  • o2_device_at_36_weeks - Respiratory support requirement at 36 weeks PMA
  • multiple_births - Multiple birth status (yes/no)
  • public_insurance - Insurance type (private/public)
  • c_section - Delivery method (vaginal/cesarean)

Feeding Outcome Variables

Timing Variables:

  • pma_at_first_oral_feeding - PMA at first oral feeding (weeks)
    • Formula: gestational_age_weeks + (date_of_first_oral_feed - birth_date)/7
  • pma_at_full_oral_feeding - PMA at full oral feeding (weeks)
    • Formula: gestational_age_weeks + (date_of_last_tube_feed - birth_date)/7
  • time_to_first - Days from birth to first oral feeding
    • Formula: date_of_first_oral_feed - birth_date
  • time_to_fof - Days from first oral feeding to full oral feeding
    • Formula: date_of_last_tube_feed - date_of_first_oral_feed

Quality Control Variables:

  • feed_delta - Alternative calculation of time to FOF for data validation

Derived Analysis Variables

Clinical Stratification:

  • early_feeder - PMA at first oral feeding < 35 weeks
  • extremely_preterm - Gestational age < 28 weeks

Missing Data Handling:

  • birth_weight_grams - GA-specific median imputation for 110 missing values (40.3% of original 273 subjects)

Full reports: https://christopherseaman.github.io/oof/