Fortification Recommendation for 35-Week Twin Infants
Yes, fortify the expressed breastmilk to 24 kcal/oz for your 35+2 week twin infants weighing approximately 4 pounds each. These late preterm infants fall into a high-risk category for inadequate growth and readmission, and fortification is both appropriate and beneficial at this gestational age and weight.
Rationale Based on Guidelines
Your twins are classified as late preterm infants (34-36 weeks gestation), a population specifically identified by AAP guidelines as having decreased breastfeeding rates, maternal delayed lactation, and inadequate milk intake that contributes to longer hospital stays and higher readmission rates 1. At approximately 1800 grams (4 pounds) each, they are above the very low birth weight threshold (<1500g) but still require enhanced nutrition for catch-up growth.
Why Fortification is Indicated
Key clinical considerations:
Late preterm infants have immature feeding mechanics and decreased effective milk emptying, leading to suboptimal caloric intake even when breastmilk is available 1
Expressed breastmilk has highly variable caloric density - studies show only 34% of samples fall within 10% of the assumed 20 kcal/oz, with actual measurements averaging 17.9 kcal/oz 2. This means your infants may be receiving significantly fewer calories than you think
Standard fortification to 24 kcal/oz provides:
- Enhanced protein for neurodevelopment and lean body mass accretion
- Increased caloric density to support catch-up growth
- Better mineral content for bone mineralization
Practical Implementation
Start fortification now using a standard bovine-derived or human milk-derived fortifier to achieve 24 kcal/oz:
- Add fortifier according to manufacturer instructions (typically 1 packet per 50-100 mL of expressed breastmilk)
- Monitor weight gain closely - target 15-30 grams/day
- Continue fortification until the infants demonstrate consistent weight gain and reach approximately 3-4 kg or term-corrected age
Important caveats:
- The assumed nutrient content after fortification often overestimates actual intake by 5-10% 3, so don't be surprised if growth is slower than calculated
- Protein concentration increases less than other macronutrients with standard fortification 4, which is why individualized approaches are emerging but not yet standard practice
- Recent evidence suggests individualized fortification (adjusting based on milk analysis) likely increases growth parameters with moderate certainty 5, but this requires specialized equipment not typically available at home
Monitoring and Follow-up
Track these parameters weekly:
- Weight gain (should be 15-30 g/day)
- Length and head circumference growth
- Feeding tolerance (no excessive spitting up, adequate stool output)
- Signs of adequate hydration
When to stop fortification:
- Infants reach approximately 3-4 kg (6.5-9 pounds)
- Consistent growth along their curve for 2-4 weeks
- Approaching term-corrected age with robust direct breastfeeding
The AAP specifically recommends that supplementation for late preterm infants should preferably be with expressed maternal milk when necessary 1, and fortification of your expressed milk is the logical extension of this principle to optimize nutrition while maintaining the immunologic and developmental benefits of human milk.
Human milk-derived fortifiers may offer additional bioactive benefits 6, but bovine-derived fortifiers are more widely available and equally effective for growth outcomes. Either option is appropriate for your clinical scenario.