Table 1.

Fetal Growth During the Period From 17–21 Weeks’ Gestation to Delivery, Mode of Labor/Delivery, and Duration of Gestation in Low-Risk White US Women, 1987–1991

Adjusted Fetal Growtha During the Period From 17–21 Weeks to Delivery	No. of Subjects	Mean Birth Weight, g	Mode of Labor/Delivery, %			Mean Duration of Gestation, days
			Spontaneous Onset of Labor	Premature Rupture of Fetal Membranes	Induced or Prelabor Cesarean Section	All Subjects	Spontaneous Onset Only
−2 SDs or below	72	2,685	65	8	27	281 (10)b	281 (9)
Between −1 and −2 SDs	413	3,043	75	9	16	279 (11)	280 (8)
Within ±1 SD	2,243	3,515	72	8	20	278 (9)	278 (9)
Between +1 and +2 SDs	397	4,074	65	8	27	279 (8)	279 (8)
+2 SDs or above	86	4,489	65	8	27	280 (9)	280 (9)

Abbreviation: SD, standard deviation.

^aFetal growth was adjusted for sex of the fetus, parity, and maternal prepregnancy weight and height.

^bNumbers in parentheses, SD.