Record linkage to obtain birth outcomes for the evaluation of screening biomarkers in pregnancy: a feasibility study

Table 2 PAPP-A and free β-hCG results and pregnancy outcomes

Pregnancy outcome	PAPP-A ≤ 5^th percentile (MoM = 0.38)		free β-hCG ≤ 5^th percentile (MoM = 0.41)
	n/N	RR (95% CI)*	n/N	RR (95% CI)*
Gestational age
Preterm birth 24–36 weeks^†	12/78	3.44 (1.94, 6.10)	5/78	1.31 (0.55, 3.16)
Birth at ≥ 37 weeks^†	70/1555	1.0 (referent)	76/1555	1.0 (referent)
Mortality outcome
Fetal loss <24 weeks	5/17	7.41 (2.67, 20.6)	4/17	5.61 (1.87, 16.8)
Stillbirth ≥ 24 weeks	0/16	not calculated	0/16	not calculated
Livebirth	82/1617	1.0 (referent)	81/1617	1.0 (referent)
Birthweight for gestational age
SGA^† (<10^th percentile)	13/131	2.08 (1.23, 3.53)	12/131	1.93 (1.11, 3.34)
≥ 10^th percentile	69/1499	1.0 (referent)	69/1499	1.0 (referent)
Composite outcome
Fetal loss, stillbirth, birth <37 wks or SGA^††	27/228	2.41 (1.72, 3.39)	20/228	1.77 (1.18, 2.65)
Livebirth ≥ 10^th percentile	60/1422	1.0 (referent)	65/1422	1.0 (referent)

* relative risk of respective pregnancy outcome given a PAPP-A or free β-hCG ≤ 5^th percentile
† small for gestational age, includes stillbirths
†† small for gestational age

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