Table 1.

Subject Characteristics at Birth and at Baseline Images

Characteristics	Mean (SE) Valuea		P Value
	Male Infants (n = 39)b	Female Infants (n = 48)c
Characteristics at birth
Postmenstrual age, wk	38.5 (0.4)	38.8 (0.3)	.51
Weight, kgd	3.2 (0.1)	3.2 (0.1)	.90
Length, cme	50.6 (0.5)	50.2 (0.4)	.58
Head circumference, cmf	34.1 (0.4)	34.3 (0.3)	.76
Birth by vaginal/cesarean delivery, No.g	26/11	29/13	.49
Apgar score
At 1 min	7.6 (0.2)	8.0 (0.2)	.21
At 5 min	8.8 (0.1)	8.9 (0.1)	.20
Mother’s age at delivery, y	28.2 (1.0)	30.1 (0.9)	.15
Maternal weight gain, kg	13.6 (0.9)	15.0 (1.3)	.36
Characteristics at baseline imaging
Postmenstrual age, wk	40.8 (0.4)	40.5 (0.3)	.52
Weight, kg	3.6 (0.1)	3.5 (0.1)	.43
Length, cm	52.1 (0.5)	51.3 (0.4)	.19
Head circumference, cm	36.0 (0.3)	35.3 (0.2)	.07

^aData represent mean (SE) values except for delivery type.

^bAll 39 male infants had baseline images, and 29 had 1 follow-up image: 8 had just 1 follow-up image, 16 had 2, and 5 had 3 (total of 94 time points).

^cAll 48 female infants had baseline images, and 38 had 1 follow-up image; 10 had just 1 follow-up image, 25 had 2, and 3 had 3 (total of 117 time points).

^dBirth weight was available for only 38 male and 47 female infants.

^eBirth length was available for only 34 male and 46 female infants. The value for boys is similar to World Health Organization data¹⁰ (WHO length, 49.88 cm; P = .16), but the value for girls is significantly higher (WHO length, 49.15 cm; P = .01).

^fHead circumference at birth was available for only 30 male and 35 female infants. The values for both boys and girls are similar to WHO data¹⁰ (boys, 34.46 cm [P = .38]; girls, 33.88 cm [P = .17]).

^gType of delivery was not known for 2 male and 6 female infants.