Changes in Serum Concentrations of Bone Turnover Markers in Healthy Pregnant Women

Table 3

Reference interval of BTMs at different stages of pregnancy.

		Lower	Upper	90% CI for lower limit	90% CI for upper limit
PINP (ng/ml)	First trimester	23	91	(18, 28)	(80, 106)
	Second trimester	12	115	(7, 21)	(90, 168)
	Third trimester	21	192	(6, 23)	(168, 229)
N-MID (ng/ml)	First trimester	5.3	16.5	(3.3, 5.7)	(15.1, 17.7)
	Second trimester	2.6	17.2	(1.7, 4.2)	(14.9, 21.0)
	Third trimester	3.9	21.5	(2.3, 5.0)	(20.0, 24.7)
β-CTX (pg/ml)	First trimester	112	462	(65, 123)	(445, 505)
	Second trimester	118	638	(97, 125)	(528, 972)
	Third trimester	149	698	(96, 163)	(656, 768)
β-CTX/PINP	First trimester	2.4	11.1	(2.0, 2.8)	(8.7, 21.4)
	Second trimester	2.8	16.2	(2.1, 3.4)	(14.2, 17.8)
	Third trimester	1.9	14.3	(1.7, 2.6)	(13.5, 23.8)
β-CTX/N-MID	First trimester	11.3	49.8	(9.9, 13.0)	(40.2, 83.2)
	Second trimester	15.8	62.3	(15.1, 18.4)	(59.6, 70.2)
	Third trimester	16.5	65.3	(12.5, 19.0)	(62.3, 69.5)

PINP, procollagen type I N-propeptide; N-MID, N-terminal osteocalcin; β-CTX, C-terminal telopeptide of type I collagen.