Table 3.

Concordance between prepregnancy BMI category estimated using self-reported prepregnancy weight versus weight measured CLOSEST to conception

2000–2010 Pregnancies (n = 16,227)
BMI Category based on self-reported weight (row %)	BMI Category based on weight measured closest to conceptiona
	Underweight	Normal Weight	Overweight	Obesity	Row Total	Crude agreement	Kappa Statistic	SE %	SP%	PPV%	NPV %
Underweight	291	126	1	0	418	90.6	0.86	83.9	99.2	69.6	99.6
	69.6%	30.1%	0.2%	0%	2.6%
Normal Weight	56	7028	660	6	7750			95.5	91.9	90.7	96.1
	0.7%	90.7%	8.5%	0.1%	47.8%
Overweight	0	202	3519	370	4091			82.3	95.2	86.0	93.8
	0%	4.9%	86.0%	9.0%	25.2%
Obesity	0	1	96	3871	3968			91.1	99.2	97.6	96.9
	0%	0%	2.4%	97.6%	24.5%
Column Total	347	7357	4276	4247	16,227
	2.1%	45.3%	26.4%	26.2%	100%
2015–2016 Pregnancies (n = 3943)
BMI Category based on self-reported weight (row %)	BMI Category based on weight measured closest to conceptiona
	Underweight	Normal Weight	Overweight	Obesity	Row Total	Crude agreement	Kappa Statistic	SE %	SP%	PPV%	NPV %
Underweight	72	29	0	0	101	92.6	0.89	87.8	99.2	71.3	99.7
	71.3%	28.7%	0%	0%	2.6%
Normal Weight	10	1605	117	0	1732			96.3	94.4	92.7	97.2
	0.6%	92.7%	6.8%	0%	43.9%
Overweight	0	33	886	77	996			86.1	96.2	89.0	95.1
	0%	3.3%	89.0%	7.7%	25.3%
Obesity	0	0	26	1088	1114			93.4	99.1	97.7	97.3
	0%	0%	2.3%	97.7%	28.6%
Column Total	82	1667	1029	1165	3943
	2.1%	42.3%	26.1%	29.6%	100%

SE sensitivity; SP specificity; PPV positive predictive value; NPV negative predictive value

^aMeasured weight closest to date of conception between 6-months-prior-to (≤ 182 days) and ≤ 42-days-after conception