Table 4.

Main Cutoffs Used in the Study of Gestational Duration

Definition	Cutoffa
	No. of Weeksb	No. of Days
Extremely premature birth	<28	<196
Very preterm birth	<32	<224
Preterm birth	<37	<259
Term birth	37–41	259–293
Postterm birth	≥42	294

^a Since the end of the last menstrual period.

^b Completed gestational weeks, corresponding to the integer part of (date of birth − date of last menstrual period)/7.