Table 2.

Characteristics of the NEC infants and control group.

	NEC		Control		P-value
	N = 24		N = 45
Gestational age (weeks)	27.2	(25.6 to 28.2)	27.4	(26.0 to 28.4)	0.733U
Birth weight (grams)	900	(773 to 1,053)	950	(780 to 1,080)	0.450x
Birth weight (z-score)a	−0.95	(−1.64 to 0.10)	−0.57	(−1.29 to 0.04)	0.455x
Sex (male)	17	(71%)	27	(60%)	0.373x
Multiples	7	(29%)	13	(29%)	0.981x
SGA (< p10)	7	(29%)	12	(27%)	0.825x
Apgar score (5 min)	7	(6 to 8)	7	(6 to 8)	0.822x
Antibiotic exposureb	24	(100%)	44	(98%)	1.000F
Days	5	(2.5 to 11)	4	(2 to 8)	0.275U
Within 24 h (yes)	21	(88%)	38	(84%)	1.000F
Mother milk in the first 7 days	22	(92%)	43	(96%)	0.606F
NICU stay (days)	45	(22 to 58)	34	(28 to 53)	0.870U
Sepsis	3	(13%)	3	(7%)	0.344F
Mortality	7	(29%)	3	(7%)	0.011x
Maternal	N = 23		N = 41
Primiparous	14	(61%)	26	(63%)	0.840x
Mode of delivery (CS)	9	(39%)	19	(46%)	0.577x
Preeclampsia or HELPP	4	(17%)	4	(10%)	0.443F
Antenatal steroids	22	(96%)	38	(93%)	1.000F
Antenatal antibiotics	12	(52%)	29	(73%)	0.103x
Placental abnormalities	18	(82%)	29	(78%)	0.729F
Necrotizing enterocolitis
Age at onset NEC (days)	13	(9 to 25)	n.a.
NEC as cause of death	6	(86%)	n.a.
Bell stage IIA	14	(58%)	n.a.
Bell stage IIB	3	(13%)	n.a.
Bell stage III	7	(29%)	n.a.
Treatment, conservative	15	(63%)	n.a.
Treatment, surgical	9	(38%)	n.a.

Characteristics given as median and (IQR) or frequency and (percentage).

SGA, small for gestational age, defined as a birth weight < p10; NICU, neonatal intensive care unit; CS, cesarean section; HELPP, Haemolysis Elevated Liver enzymes and Low Platelets syndrome; NEC, necrotizing enterocolitis; n.a., not applicable.

^aAccording to Dutch Perined reference values (33).

^bAntibiotic exposure from birth until the date of the taken stool sample.

^UMann-Whitney U-Test,

^tStudents T-test,

^xChi-square Test,

^FFisher's Exact Test.