Biochemical Placental Function Tests for Foetal Assessment

A Cochrane review [Abstract] 2 included 91 studies that evaluated 7 tests (blood tests for human placental lactogen (hPL), oestriol, placental growth factor (PlGF) and uric acid, ultrasound estimated foetal weight [EFW] and placental grading and urinary oestriol) in a total of 175426 pregnant women. The quality of included studies was variable with most domains at low risk of bias although 59% of studies were deemed to be of unclear risk of bias for the reference standard domain. Ultrasound EFW was the most accurate test for detecting small for gestational age (SGA) (86 studies; n=15 471) at birth with a diagnostic odds ratio (dOR) of 21.3 (95% CI 13.1 to 34.6); hPL was the most accurate biochemical test with a dOR of 4.78 (95% CI 3.21 to 7.13). In a hypothetical cohort of 1000 pregnant women, at the median specificity of 0.88 and median prevalence of 19%, EFW, hPL, oestriol, urinary oestriol, uric acid, PlGF and placental grading will miss 50 (95% CI 32 to 68), 116 (97 to 133), 124 (108 to 137), 127 (95 to 152), 139 (118 to 154), 144 (118 to 161), and 144 (122 to 161) SGA infants, respectively. For the detection of pregnancies ending in stillbirth (21 studies; n=100 687 pregnancies involving 740 stillbirths), in an indirect comparison of the 4 biochemical tests, PlGF was the most accurate test with a dOR of 49.2 (95% CI 12.7 to 191). No studies assessed the accuracy of ultrasound EFW for stillbirth.

Another Cochrane review [Abstract] 3 included 2 trials with a total of 740 women. There was no evidence of a difference in the incidence of stillbirth or neonatal death (RR 0.88, 95% CI 0.36 to 2.13) or the frequency of SGA (RR 0.44, 95% CI 0.16 to 1.19).

A Cochrane review [Abstract] 1 included one trial of poor quality, with a total of 622 women. Women were allocated to have their estriol results revealed or concealed on the basis of hospital record number (with attendant risk of selection bias). There were no obvious differences in perinatal mortality (relative risk (RR) 0.88, 95% confidence interval (CI) 0.36 to 2.13) or planned delivery (RR 0.97, 95% CI 0.81 to 1.15) between the two groups.

References

• Neilson JP. Biochemical tests of placental function for assessment in pregnancy. Cochrane Database Syst Rev 2003;(2):CD000108 (Last assessed as up-to-date: 27 June 2012). [PubMed]
• Heazell AE, Hayes DJ, Whitworth M et al. Biochemical tests of placental function versus ultrasound assessment of fetal size for stillbirth and small-for-gestational-age infants. Cochrane Database Syst Rev 2019;(5):CD012245. [PubMed]
• Heazell AE, Whitworth M, Duley L et al. Use of biochemical tests of placental function for improving pregnancy outcome. Cochrane Database Syst Rev 2015;(11):CD011202. [PubMed]