Table 1.

Characteristics of North or South Carolina residents who gave birth in North Carolina or enrolled in Early Check from September 17, 2018, through March 19, 2019 (N = 56,457)

Characteristic	n	%
Enrolled in Early Check
Postnatal	2,219	3.9
Prenatal	38	0.1
Did not enroll	54,200	96.0
Outreach methods
Recruitment letter
Sent a recruitment letter	53,716	95.1
No recruitment letter sent	2,741	4.9
Personalized email invitation
Sent a personalized email invitation	3,476	6.2
Not sent an email invitation	52,981	93.8
Reminder postcard
Sent a reminder postcard	6,425	11.4
Not sent a reminder postcard	50,032	88.6
State of residence
North Carolina	55,268	97.9
South Carolina	1,189	2.1
Urbanicity
Urban	45,861	81.2
Rural	10,575	18.7
Unknown	21	0.1
Birth hospital affiliation
Yes, affiliated with an Early Check research partner	10,018	17.7
No, not affiliated with an Early Check research partner	46,439	82.3

In the case of multiple births and repeat samples, we used location data from the earliest record for each mother to establish residency.