Table 1 Comparisons of demographic and birth characteristics between our study population and the original study participants who were lost to follow-up.

Characteristic	Levels	Lost to follow-up	Follow-up study	P value
n		1552	632
Sex	Males	876 (56.4%)	292 (46.2%)	< 0.001
Sex	Females	676 (43.6%)	340 (53.8%)
Birth weight z-score		− 0.32 ± 0.92	− 0.46 ± 0.92	0.001
Gestational age (weeks)		38.8 ± 2.0	39.0 ± 1.7	0.022
Delivery by caesarean section		57 (9.0%)	176 (11.3%)	0.13
Maternal age at childbirth (years)		25.3 ± 4.6	26.3 ± 4.6	< 0.001
Maternal BMI (kg/m²)^a		21.51 ± 2.86	21.34 ± 2.51	0.19
Maternal PIH^b		40 (2.6%)	25 (4.0%)	0.10
Maternal smoking at pregnancy		14 (0.9%)	5 (0.8%)	> 0.99
Maternal alcohol consumption during pregnancy		11 (0.7%)	7 (1.1%)	0.43
Maternal education^c	Less than high school	1127 (89.2%)	491 (90.3%)	0.56
Maternal education^c	High school or greater	136 (10.8%)	53 (9.7%)
Paternal education	Less than high school	1036 (82.1%)	439 (80.7%)	0.51
Paternal education	High school or greater	226 (17.9%)	105 (19.3%)
Family income (baht per month)^d		2918 [1800, 4500]	2500 [1563, 4200]	0.005

Continuous data are means ± SD or median [quartile 1, quartile 3], as appropriate; categorical data are n (%).
BMI body mass index, PIH pregnancy-induced hypertension.
P values that are statistically significant (at p < 0.05) are shown in bold.
^aBMI recorded at the first antenatal visit in the original study in 1989–1990.
^bPIH was defined as a systolic blood pressure ≥ 140 mmHg and/or diastolic blood pressure ≥ 90 mmHg developed after 20 weeks of gestation without proteinuria, in a previously normotensive woman.
^cThere were missing data on the highest levels of education, so that the available sample sizes for the Follow-up and Lost to follow-up groups were 544 (86.1%) and 1263 (81.4%) for maternal education, respectively, and 544 (86.1%) and 1262 (81.3%) for paternal education.
^dIncome recorded at the time of maternal recruitment to the original study in 1989–1990 (i.e., not adjusted for inflation); the available sample sizes were 542 (85.8%) for the follow-up group and 1230 (79.3%) for those lost to follow-up.

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