Case-control study of milk curd obstruction in newborn infants in a tertiary surgical neonatal intensive care unit.

Background: Milk curd obstruction (MCO), in which milk becomes inspissated, is a rare, serious, complication of preterm birth. Case reports implicate male sex and bovine-derived human milk fortifier (HMF) use as predisposing factors. We investigated this through a case-control study.

Methods: MCO cases in the Starship Child Health neonatal database between 2008 and 2020 were matched with controls in a 1:2 ratio based on gestational age (±1 week), birth weight (±200 g) and date of birth (±1 month). Data were analysed using the Student's t-test, Mann-Whitney U-test or χ² test as appropriate. Data are median (IQR) or n (%).

Results: Of 20 MCO cases, gestation was 26.1 (24.5-28.1) weeks, birth weight was 822 (713-961) g, 15 (75%) were male. 40 controls were well-matched for gestation (26.1 (24.8-27.9) weeks) and birth weight (849 (690-1066) g) but only 18 (45%) were male (p=0.05). MCO occurred at 21 (15-33) days; 6 (30%) cases died compared with 3 (7.5%) controls (p=0.06). HMF was commenced at 243 (150-309) hours in cases and 224 (172-321) hours in controls (p=0.95); full-fortification (manufacturer's recommended dose) was achieved in 8 (40%) cases and 27 (68%) controls (p=0.08). In cases, MCO occurred 10 (7-17) days after commencing HMF. Medically/surgically-managed gut pathology occurred in 7 (35%) cases prior to MCO but in no controls (p<0.001).

Conclusions: Our data support male sex but not HMF use as a predisposition to MCO. Evidence of prior medical/surgical gut pathology may be a premonition for MCO; however, further research is required to confirm this.