Free carnitine levels in peripheral blood of healthy pregnant women in third trimester and their relationship with maternal and fetal cardiac function and structure / 中华围产医学杂志

ABSTRACT

Objective:To investigate the levels of periphreal blood free carnitine and amino acids in healthy pregnant women in the third trimester and their association with maternal, fetal, and neonatal cardiac function and structure.Methods:This prospective descriptive study included healthy singleton pregnancies who underwent routine obstetric examination and delivered in two district maternal and child health hospitals (one in the urban and one in the suburb an area) in Beijing from June 2017 to February 2018. All recruiters had serology Down's syndrome screening test at (18±1) gestational weeks. Besides measurement of amino acids and free carnitine levels in whole blood and urine samples by liquid chromatography-tandem mass spectrometry, all cases underwent maternal and fetal echocardiography at (35±1) weeks of gestation. And neonatal echocardiography was performed after delivery to assess the heart function and structure. Antenatal factors were also collected, including maternal education background, age at first marriage and conception, gravidity, and folic acid supplement in early pregnancy. Statistical analysis was performed using t-test, ANOVA, Chi-square test, Pearson correlation coefficient, and Kappa test. Results:A total of 493 mother-neonate dyads were enrolled in this study. Blood free carnitine levels in the healthy pregnant women in the third trimester ranged from 5.09 to 59.17 μmol/L (reference value: 10.00-50.00 μmol/L) with an average value of (13.03±3.87) μmol/L. None was found with structural abnormalities by cardiac ultrasound, showing an average left ventricular end diastolic diameter (LVEDD) and end systolic diameter (LVESD) of (45.70±3.08) mm and (29.17±3.12) mm, respectively, and left ventricular ejection fraction (LVEF) of all cases were over 55%. No cardiac malformation was detected by the third-trimester fetal echocardiography. The average birth weight of the 493 newborns was (3 340±313) g. Those whose birth weight <2 500 g and >4 000 g were accounted for 1.0% (5 cases) and 3.0% (15 cases) with the average maternal blood free carnitine level of (13.25±2.17) μmol/L (10.46-19.21 μmol/L) and (12.64±2.50) μmol/L (8.78-17.73 μmol/L) ( t=0.42, P>0.05). The average LVEDD and LVESD of the 493 newborns were (17.21±1.27) mm and (11.03±1.30) mm, respectively. For the 64 newborns (13.0%) whose LVEF<60%, the maternal blood free carnitine level was (12.93±2.78) μmol/L (7.34-22.13 μmol/L), showing no statistical difference ( t=-0.29, P>0.05) with those 59 neonates (12.0%) whose LVEF over 75% and maternal carnitine level of (13.09±3.24) μmol/L (8.66-27.49 μmol/L). All cases were divided into four groups based on the quartiles of maternal blood free carnitine level and no significant difference in maternal or neonatal LVEDD or LVEF was observed among these groups (all P>0.05). Conclusions:Blood free carnitine concentration in healthy pregnant women in the third trimester is at the lower limit of normal range, and no significant effect on maternal cardiac function and fetal cardiac structure is seen. However, the effect of low maternal carnitine level in the third trimester on children's myocardial function and whether carnitine should be supplemented in the third trimester are worthy of further investigation with larger sample size.