Table 2. Sample descriptive statistics (no imputations).

Variable	N	Mean	Std. Dev.	Minimum	Median	Maximum
Child birth weight (ounces)	109	119.39	18.41	79.4	121.4	176
Low birth weight status	110	0.045	0.21	0	0	1
Gestational age (in days)	110	272.08	12.24	212.1	273.7	290.5
No. of cigarettes smoked/day	139	2.60	6.53	0	0	30
Maternal race (nonwhite=1)	137	0.15	0.36	0	0	1
Maternal age in years	139	29.7	5.41	18.8	30.7	40.7
Bayley's mental score - 3 mo	119	102.9	3.9	93	103	125
Bayley's motor score - 3 mo	119	101	4.49	85	101	108
Pre-pregnancy weight (in lbs)	108	182.4	84.7	126	176	306
Weight gain (in lbs)	101	32.9	18.9	7	31	91.9
Education > high school	137	0.9	0.3	0	1	1
Maternal prior parity	140	0.96	1.10	0	1	6
Household income	137	7.4	1.9	1	8	9
Mother had diabetes	140	0.05	0.22	0	0	1
Child female sex	91	0.49	0.50	0	0	1
Pregnancy interval	140	3914.1	4514.4	15	1024	13533
First primary care visit	136	63.1	23.7	12	61	135

Note: To have a fully observed weight gain outcome for each woman, it is necessary to know both the pre-pregnancy and delivery weights. Thus, although delivery weights were missing for only 31 women, 39 women had missing weight gain outcomes.