Maternal Homocysteine Level and Markers Used in First-Trimester Screening for Fetal Down Syndrome

Assessment of blood one-carbon metabolism indexes during mid-to-late pregnancy in 397 Chinese pregnant women

Objectives

One-carbon metabolism (OCM) significantly influences fetal growth and neurodevelopment through transferring methyl group to biomolecules, during which folate, methionine, choline and betaine function as methyl donor nutrients, while vitamin B2, B6, B12 function as enzyme cofactors, and homocysteine (Hcy) and S-adenosyl methionine (SAM) are functional metabolites. This study aimed to assess blood OCM index levels and explore their relationships among Chinese pregnant women.

Methods

Data were obtained from the baseline of the Mother-Child Nutrition and Health Cohort Study. Pregnant women, voluntarily recruited from September 2020 to June 2022 during antenatal examinations in five Chinese cities at 24-32 gestational weeks, provided fasting venous blood samples. Measurements included RBC and serum folate, serum vitamin B2, B6, B12, choline, betaine, methionine, total Hcy (tHcy), and plasma SAM. Sociodemographic characteristics and pregnancy-related conditions were collected via a self-designed questionnaire.

Results

Of 397 participants, 82.6% were in mid-pregnancy (24-27 gestational weeks) and 17.4% were in late-pregnancy (28-32 gestational weeks). Serum folate, vitamin B6, and B12 deficiencies were 2.5, 1.3, and 8.3%, respectively. Elevated tHcy (≥10 μmol/L) was observed in 1.8% of pregnant women. Elderly pregnant women (aged 35 and above) exhibited significantly lower serum methionine levels (p < 0.05), while multiparous women had lower RBC folate levels (p < 0.05), and lower serum methionine and vitamin B12 levels (p < 0.10, not statistically significant). Partial correlation analysis revealed positive associations between RBC folate and cofactor vitamin B12 (r = 0.244, p < 0.05) in the folate cycle, as well as significant correlations between two methyl donor paths [serum folate was significantly related to serum choline (r = 0.172) and betaine (r = 0.193)]. As functional biomarkers of OCM, serum tHcy exhibited negative associations with RBC folate (β = -0.330, p < 0.05) and vitamin B6 (β = -0.317, p < 0.05), and plasma SAM displayed a positive association with serum betaine (β = 0.610, p < 0.05), while negatively associated with serum vitamin B6 (β = -0.181, p < 0.05).

Conclusion

The blood OCM exhibited imbalances during mid-to-late pregnancy, characterized by lower levels of folate, vitamin B6, and B12, alongside elevated tHcy levels. Adequate folate and vitamin B6 emerged as significant predictors of lower tHcy levels. Additionally, serum betaine showed a positive correlation with plasma SAM. This suggests the importance of not only ensuring sufficient folate but also optimizing other OCM-related nutrients throughout pregnancy.

Prognostic Value of Cardiovascular Disease Risk Factors Measured in the First-Trimester on the Severity of Preeclampsia

Recent studies have suggested that preeclampsia and cardiovascular disease may share common mechanisms. The purpose of this prospective nested case-controlled study was to characterize a variety of cardiovascular disease risk factors measured during the first trimester of pregnancy in predicting subsequent outcomes and the severity of preeclampsia.We ascertained the severity of preeclampsia at the onset of the disease, and the presence of intrauterine growth restriction (IUGR). We compared first trimester maternal serum cardiovascular disease risk factors in preeclampsia subjects versus normal pregnancies, early-onset versus late-onset preeclampsia, and preeclampsia with IUGR versus without IUGR. To identify the prognostic value of independent predictors on the severity of preeclampsia, we calculated the area under the receiver operating characteristics curve (AUC) using logistic regression analysis.There were 134 cases of preeclampsia and 150 uncomplicated pregnancies, and preeclampsia cases were classified as early-onset (53 cases) or late-onset (81 cases), or as with IUGR (44 cases) or without IUGR (90 cases). Among the cardiovascular disease risk factors, maternal serum high-sensitive C-reactive protein (hsCRP) and homocysteine were predictors of both early-onset preeclampsia and preeclampsia with IUGR. For the detection of early onset preeclampsia or preeclampsia with IUGR, the AUC for the combination model (0.943 and 0.952, respectively) was significantly higher than with serum hsCRP or serum homocysteine only.Patients with preeclampsia can be subdivided into different severities according to time of onset and fetal weight. Cardiovascular risk factors distinguish a subgroup of these patients.

First-trimester combined screening is effective for the detection of unbalanced chromosomal translocations at 11 to 12 weeks of gestation

The first trimester combined screening, which analyzes fetal nuchal translucency and levels of free β-human chorionic gonadotropin (β-hCG) and pregnancy-associated plasma protein A (PAPP-A) in maternal serum, is routinely used to detect abnormal pregnancies associated with Down syndrome and other trisomy aneuploidies. Based on the hypothesis that major chromosomal translocations could lead to similar biochemical and developmental outcomes during early embryo development, we compared these markers among pregnancies with normal, balanced, or unbalanced fetal karyotypes. Among the parents, 71 (73%) carry balanced reciprocal translocation and 26 (27%) have Robertsonian translocation. Of the 97 pregnancies tested, 39 (40%), 37 (37%), and 22 (23%) fetuses had normal karyotype, balanced chromosomal translocations, and unbalanced chromosomal translocations, respectively. Importantly, we found that pregnancies with an unbalanced translocation had significantly higher free β-hCG multiple of the median (MoM) and larger nuchal translucency thickness than those with normal karyotype or balanced translocations. Analysis showed that the area under a receiver operating characteristic curve (AUC) is 0.716, 0.820, and 0.936 for free β-hCG MoM, PAPP-A MoM, and fetal nuchal translucency, respectively. When these 3 independent factors were combined, the AUC reached 0.976. In addition, logistic regression showed that the most optimal model for predicting an unbalanced chromosomal translocation is a combination of PAPP-A and nuchal translucency with an AUC of 0.980. Therefore, the first trimester combined screening is not only effective in the screening of Down syndrome and other trisomy abnormalities but also has high sensitivity for the detection of unbalanced chromosomal translocations in fetuses.