Table 1.

California breast milk studies.

Study	CS CA	ST	LT	0–28 DABa	29–56 DABa
No.	82	9	9	35	35
Study period	Mar 2003–Nov 2005	Oct 2004–Jun 2005	Mar 2003–Sep 2005	Apr 2003–Sep 2005	Apr 2003–Nov 2005
Duration	130 weeks	24 weeks	Variable	4 weeks	4 weeks
Design	Primiparae; infant 2–8 weeks; samples hand-expressed	CS CA subset; 5–7 serial samples 4, 6, 8, 12, 16, 20, 24 weeks; 6 weeks, concurrent HE/P	CS CA subset; 2 samples: first at 1–6 weeks; second at 18–136 weeks	CS CA subset; samples collected 0–28 DAB	CS CA subset; samples collected 29–56 DAB
Demographics
Median age (years)	31	29	32	32	30
Race (%)
African American	9	10	5	9	6
Latina	12	10	10	9	14
Asian	5	10	5	3	6
White	71	60	80	80	66
Education (%)
< High school graduate	4	10	0	6	0
High school graduate	8	0	0	11	6
Some college	19	30	15	14	31
College graduate	70	60	85	69	63
Median BMI	22.7	21.9	24	23.6	22.5
Family income (%)
< $18,000	15	10	10	11	20
$18,001–$36,000	12	70	25	17	34
$36,001–$60,000	12	0	5	20	6
≥ $60,001	43	20	50	51	29
Infant sex [% (F/M)]	60/40	56/44	56/44	63/37	54/46
Median birth length (in.)	20	20.5	20	20	20.5
Median birth weight (lb)	7.5	7.5	7.4	7.7	8
Smoking status (%)
Current smoker	3	10	5	3	3
Ex-smoker	43	40	10	37	46
Never-smoker	54	50	90	60	51
Breast-fed as child [% (yes/no)]	72/20	70/20	70/30	71/20	63/23
California residence (%)
> 5 years	77	70	80	97	89
< 5 years	23	30	20	3	11

Abbreviations: BMI, body-mass index [weight (kg)/height (m)²]; DAB, days after birth.

^aDepuration rates early in lactation, (0–28 DAB) were compared with rates later in lactation (29–56 DAB) using two groups of mothers from the CS CA study, in which one group collected initial samples 3–28 DAB (n = 35), and a second group 29–56 DAB (n = 35).