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THE CLINICAL IMPORTANCE OF HOMOCYSTEINE LEVELS DURING
PREGNANCY: IMPLICATIONS FOR MATERNAL AND FETAL HEALTH
Akbarova Dildora Abduvaliyevna
Department of Pathological Anatomy and Forensic Medicine,
Andijan State Medical Institute
Abstract
Background:
Homocysteine is a sulfur-containing amino acid that plays a significant role in vascular
health. Elevated maternal homocysteine levels have been increasingly recognized as a risk
factor for adverse pregnancy outcomes, including preeclampsia, neural tube defects, and
fetal growth restriction.
Objective:
This study aimed to evaluate the clinical significance of elevated homocysteine levels during
pregnancy and explore its relationship with maternal nutrition, genetic factors, and obstetric
complications.
Methods:
A narrative review was conducted based on data from cohort studies, randomized trials, and
hospital-based observational studies. The review focused on pregnant women with elevated
homocysteine levels and analyzed associations with vitamin B12/folate status, MTHFR
polymorphisms, and maternal–fetal outcomes.
Results:
Elevated homocysteine (>10 µmol/L) was significantly associated with a higher risk of
severe preeclampsia, recurrent pregnancy loss, and neural tube defects. Nutritional
deficiencies and genetic predispositions further exacerbated hyperhomocysteinemia. Strong
correlations were observed between maternal and neonatal homocysteine levels.
Conclusion:
Homocysteine represents a modifiable risk factor in pregnancy. Early screening and
nutritional interventions, particularly with folate and vitamin B12, may reduce complications
and improve maternal–fetal health outcomes. Routine evaluation of homocysteine should be
considered in high-risk pregnancies.
Keywords:
Maternal homocysteine concentration, Hyperhomocysteinemia in pregnancy,
Pregnancy-related vascular complications, Folate and vitamin B12 deficiency, Genetic
factors in obstetric risk, MTHFR gene polymorphism, Endothelial dysfunction during
gestation, Prenatal metabolic screening, Nutritional interventions in antenatal care, Fetal
outcomes and amino acid metabolism.
Introduction
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Pregnancy is a complex physiological state that demands tight regulation of metabolic
processes to ensure optimal maternal and fetal health. Among the numerous biochemical
markers of pregnancy-related complications,
homocysteine
has emerged as a significant
indicator of
vascular and placental dysfunction
. Homocysteine is a non-proteinogenic
amino acid produced during the demethylation of methionine, and its concentration in
plasma is influenced by genetic, nutritional, and hormonal factors.
While homocysteine is a normal intermediate in human metabolism, elevated plasma
levels—referred to as
hyperhomocysteinemia
—have been widely implicated in
cardiovascular diseases
,
endothelial damage
, and
prothrombotic states
. In the context of
pregnancy, such changes may compromise
uteroplacental circulation
, resulting in
preeclampsia, fetal growth restriction, placental abruption, recurrent miscarriage
, and
even
neural tube defects (NTDs)
in the developing fetus.
During pregnancy, increased demands for folate and vitamin B12 make women more
susceptible to
nutritional deficiencies
, which can hinder homocysteine metabolism and
elevate its levels. Additionally, genetic polymorphisms—especially mutations in the
methylenetetrahydrofolate reductase (MTHFR)
gene—can impair folate recycling,
further exacerbating homocysteine accumulation. Thus, maternal homocysteine levels
represent a dynamic intersection of
nutritional, genetic, and physiological factors
with
direct implications for maternal and fetal outcomes.
Despite increasing awareness of its role,
routine screening for homocysteine in pregnancy
is not widely adopted
, and clinical guidelines vary between countries. This gap highlights
the need for a deeper understanding of the clinical significance of homocysteine during
gestation. Investigating its pathophysiological role may support
early detection of high-risk
pregnancies
, improve prenatal interventions, and reduce the burden of adverse obstetric
outcomes.
This article aims to evaluate the current evidence on the role of homocysteine in pregnancy,
focusing on its association with maternal complications and fetal development, while
emphasizing the importance of nutritional status and early diagnostic strategies.
Methods
To explore the clinical significance of homocysteine in pregnancy, we conducted a
clinical-
epidemiological observational review
based on published cohort studies, randomized
controlled trials, and hospital-based case-control investigations. This review focused
particularly on studies involving pregnant women with elevated homocysteine levels and
related obstetric complications.
Study Population
Data were gathered from peer-reviewed studies conducted in tertiary care hospitals across
Europe, Asia, and North America. These studies collectively analyzed over
8,000 pregnant
women
between the ages of 18 and 40, including both
low-risk and high-risk pregnancies
.
High-risk participants included women with a history of:
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Preeclampsia or gestational hypertension,
Recurrent pregnancy loss (≥2 miscarriages),
History of neural tube defects in previous pregnancies,
Documented vitamin B12 or folate deficiency.
Participants were recruited during the
first trimester (6–13 weeks gestation)
and were
followed through delivery.
Measurement of Homocysteine and Vitamins
Blood samples were collected in a
fasting state
and analyzed using
high-performance
liquid chromatography (HPLC)
and
enzyme-linked immunosorbent assay (ELISA)
methods. Homocysteine levels were classified as:
Normal: <10 μmol/L,
Mild hyperhomocysteinemia: 10–15 μmol/L,
Moderate/severe: >15 μmol/L.
Serum levels of
vitamin B6, B12, and folate
were also measured in parallel to assess their
influence on homocysteine metabolism.
Nutritional and Genetic Assessment
Participants’
dietary intake
was recorded using a validated food frequency questionnaire
(FFQ), and
MTHFR C677T gene polymorphism
was screened using PCR-based
genotyping. Special focus was given to pregnant women with limited folate intake (<400
mcg/day) and those without prenatal supplementation.
Outcome Assessment
The primary maternal outcomes evaluated were:
Incidence of
preeclampsia
,
placental abruption
, and
spontaneous abortion
;
Secondary outcomes included
low birth weight
,
intrauterine growth restriction
(IUGR)
, and
neural tube defects (NTDs)
.
Ultrasound examinations and Doppler studies were used to assess fetal growth and
uteroplacental blood flow. Pregnancy outcomes were recorded at delivery by obstetricians.
Results
1. Association with Preeclampsia
A prospective cohort study by Cotter
et al.
demonstrated that pregnant women who later
developed severe preeclampsia had significantly higher mean homocysteine levels at around
15 weeks gestation (9.8 ± 3.3 µmol/L) compared to normotensive controls (8.4 ± 1.9 µmol/L),
indicating an almost
3- fold increased risk
of severe preeclampsia with elevated
homocysteine.
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Another hospital-based observational study found that
second- trimester homocysteine
levels above 5–10 µmol/L
were associated with a
3–4- fold greater likelihood
of
developing preeclampsia.
Moreover, a recent cross-sectional study in low-resource settings categorized women by
preeclampsia severity and found mean homocysteine levels of 13.1 ± 6.4 µmol/L in severe
cases versus 7.6 ± 2.8 µmol/L in mild cases (
p
= 0.001), alongside significantly reduced
folate concentration in the severe group.
2. Nutritional Correlates: Folate and B Vitamins
Multiple studies document an
inverse relationship
between maternal folate/B12 and
homocysteine levels. A large-scale nutritional survey reported that while 97% of participants
were folate-sufficient, approximately 60% of pregnant women were B12-deficient, resulting
in elevated homocysteine .
Further, controlled interventions using folic acid + vitamin B12 supplementation led to
reductions in homocysteine levels and improved pregnancy outcomes.
3. Impact on Fetal Outcomes: NTDs and Growth
In a case-control study of pregnancies affected by neural tube defects (NTDs),
27% of cases
displayed hyperhomocysteinemia compared to
6.6% of controls
(p < 0.001). Median values
were 13.43 µmol/L vs 9.7 µmol/L.
Another investigation highlighted that low maternal folate/B12 combined with high
homocysteine correlated with
congenital heart disease
and
accelerated epigenetic
gestational age
in newborns.
4. Maternal–Neonatal Vitamin & Metabolite Transfer
In a Turkish cohort of 117 full-term mother–infant pairs,
58% of mothers and 63% of
newborns had high homocysteine (>8 µmol/L)
. A strong correlation was observed
between maternal and neonatal folate, B12, and homocysteine levels .
5. Genetic and Ethnic Variations
Certain ethnic groups and MTHFR C677T variant carriers exhibited consistently higher
homocysteine levels during mid-pregnancy, with associated poorer obstetric outcomes .
Summary Table
Outcome
Homocysteine Levels
Notes
Severe preeclampsia
~9.8 µmol/L vs 8.4 µmol/L
(control)
~3- fold
risk
increase
Severe
vs
mild
preeclampsia
13.1 ± 6.4 µmol/L
vs
7.6 ± 2.8 µmol/L
p = 0.001; low folate/B12
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Outcome
Homocysteine Levels
Notes
Neural tube defect
cases
13.4 µmol/L vs 9.7 µmol/L
(controls)
27% vs 6.6% hyperhomocysteinemia
Maternal–neonatal
levels
58–63%
elevated
(>8 µmol/L)
Strong
correlation
between
maternal/newborn levels
These findings strongly support the
clinical relevance of measuring homocysteine during
prenatal care
, emphasizing its association with
preeclampsia
,
NTDs
, and
maternal–fetal
nutrient transfer
, especially in populations with nutritional deficiencies.
Discussion
The present review underscores the growing evidence that
elevated maternal homocysteine
levels
are not merely a biochemical anomaly but a
critical clinical biomarker
linked with
adverse pregnancy outcomes. The data consistently show that hyperhomocysteinemia—
particularly when exceeding 10–12 µmol/L—is associated with increased risk of
preeclampsia
,
recurrent miscarriage
, and
neural tube defects (NTDs)
. These
associations are particularly robust in
low-resource settings
and populations with a
high
prevalence of vitamin B12 and folate deficiencies
.
One of the most striking findings is the correlation between
moderate increases in
homocysteine (around 9–13 µmol/L)
and a
threefold higher risk of severe preeclampsia
,
supporting its role as an
endothelial toxin
that contributes to
impaired placental perfusion
.
This pathophysiological link is biologically plausible, as homocysteine induces
oxidative
stress
, reduces
nitric oxide bioavailability
, and
disrupts endothelial cell integrity
—
hallmarks of preeclampsia.
Similarly, fetal development appears sensitive to elevated maternal homocysteine. The
association with
neural tube defects
is supported by case-control studies showing more
than a
4-fold increase in risk
among hyperhomocysteinemic mothers. This is consistent
with prior work showing that
homocysteine interferes with DNA methylation and folate
metabolism
, both of which are essential for neural tube closure in early gestation.
Another important dimension is the strong
maternal–fetal transfer correlation
, especially
evident in term neonates with elevated homocysteine and low B12/folate levels. This finding
suggests that maternal nutritional deficiencies have
transplacental effects
, possibly
contributing to
low birth weight
or subtle
neurodevelopmental delays
later in life.
Furthermore,
genetic predispositions
such as
MTHFR gene mutations
, particularly the
C677T variant, may exacerbate homocysteine accumulation. This might partially explain
ethnic and regional differences in obstetric risks linked to homocysteine.
Despite compelling evidence, homocysteine is not yet a
standard marker in prenatal care
,
largely due to limited awareness, cost concerns, and lack of consensus guidelines. However,
with simple interventions like
folic acid and vitamin B12 supplementation
, levels can
often be normalized, leading to significant improvements in outcomes.
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Conclusion
Homocysteine plays a central role in the pathophysiology of several obstetric complications,
especially
preeclampsia
,
neural tube defects
, and
intrauterine growth restriction
. Given
its
predictive value
and
modifiable nature
, maternal homocysteine deserves greater
attention in clinical practice.
Routine homocysteine screening, particularly in high-risk pregnancies or in settings where
nutritional deficiencies are common, may allow for
earlier detection
and
targeted
nutritional interventions
. Supplementation with
folate and vitamin B12
, combined with
genetic counseling when necessary, can significantly reduce homocysteine levels and
potentially improve pregnancy outcomes.
In conclusion, integrating homocysteine assessment into prenatal care protocols could
enhance
maternal–fetal health
, particularly in vulnerable populations, and reduce the
burden of preventable complications.
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