Transient liver elastography in normal pregnancy - a longitudinal cohort study

Background and aim: Transient elastography can detect liver fibrosis by estimation of liver stiffness. Results may be falsely high when blood flow to the liver is increased, such as during late stages of pregnancy. The aim of the present study was to longitudinally evaluate transient elastography in healthy pregnant women. Methods: We recruited 24 healthy women with normal singleton pregnancies in a longitudinal cohort study. All women underwent transient elastography at gestational week 18-20, week 26-28 and week 36-38, as well as after a minimum of 8 weeks postpartum. Results: Mean age at baseline was 30.6 years ± 4.1, and mean BMI was 22.3 kg/m²±1.9. 14 women (58%) were nulliparous. The pregnancy outcomes were normal, with no cases of preeclampsia or gestational diabetes. Mean gestational length was 284 days ± 7. Mean liver stiffness increased from 3.8 kPa during the second trimester to 5.9 kPa during the third trimester (p = .002). At the third trimester, 2 women (8%) had an elastography measurement of >7.9 kPa. Postpartum, liver stiffness decreased to early second trimester levels (5.9 to 3.8 kPa, p = .002), and no woman had liver stiffness values above 7.9 kPa. Likewise, the mean Controlled Attenuation Parameter (CAP) increased from 186 dB/m in the second trimester to 215 dB/m in the third trimester (p = .01) and reversed postpartum (215 to 193 dB/m, p = .03). Conclusion: Liver stiffness and CAP increase reversibly during normal pregnancies, and slightly elevated levels in the third trimester can be considered a normal finding. Lay summary An ultrasound-based method called transient elastography can be used to measure fat content and estimate fibrosis in the liver. In this study, we examined healthy women three times during their pregnancy and once after labor to evaluate the effects of a normal pregnancy on a healthy liver. The ultrasound-estimation of fibrosis and fat content increased during pregnancy and reversed afterwards, without any other signs of disease in the liver.