Ubiquinol, the active reduced form of coenzyme Q10, has not been linked to serious adverse effects in pregnant women in the clinical trials conducted so far. The body naturally produces CoQ10 and levels actually climb throughout pregnancy, which has prompted researchers to study supplementation for conditions like preeclampsia. But the overall evidence base remains small, and no major health authority has issued a specific dosing recommendation for pregnancy.
What the Available Safety Data Shows
The most relevant clinical trial gave CoQ10 to pregnant women at risk for preeclampsia starting at 20 weeks of gestation. The study, involving about 235 women, reported no serious supplement-related side effects in the treatment group.1PubMed. Coenzyme Q10 supplementation during pregnancy reduces the risk of pre-eclampsia Outside of pregnancy, CoQ10 supplementation has been studied in trials lasting up to five years with no major adverse reactions, and the most commonly reported complaints are mild stomach upset and occasional headaches, typically at doses above 1,200 mg per day. CoQ10 is naturally present in the body and in food, which is part of why its safety profile is relatively forgiving compared to many other supplements.
That said, no large-scale randomized trial has been designed specifically to evaluate ubiquinol safety during pregnancy as its primary outcome. The safety data we have comes from trials that were measuring something else, like preeclampsia rates, and tracked side effects secondarily. This is a common situation in prenatal supplement research, and it means the evidence is reassuring but not as thorough as it could be.
One practical note: ubiquinol and ubiquinone are both forms of CoQ10, and the body converts between them. A four-week trial found that ubiquinol at 200 mg per day was about 70% more bioavailable than ubiquinone, likely because ubiquinol is more efficiently incorporated into the structures that carry fats through the gut lining.2PubMed Central. Ubiquinol in Fertility and Reproduction: A Conditionally Essential Nutrient for Critical Early-Life Stages – Section: Bioavailability and Safety Most pregnancy research has used “CoQ10” without specifying which form, though some trials used ubiquinone specifically. There is no reason to suspect the two forms differ in safety, but the bioavailability gap means that effective doses are not interchangeable between them.
Why CoQ10 Levels Naturally Rise During Pregnancy
Your body doesn’t just tolerate CoQ10 during pregnancy — it actively ramps up production. Plasma CoQ10 levels rise across all three trimesters, a pattern that has been documented repeatedly.3Fetal Diagnosis and Therapy. Coenzyme Q10 in Pregnancy This increase tracks closely with rising cholesterol levels, which makes physiological sense because CoQ10 shares part of its synthesis pathway with cholesterol and is transported in the blood by the same lipoprotein particles.4PubMed. Positive correlation between maternal serum coenzyme Q10 levels and infant birth weight
This natural rise appears to serve the growing energy demands of pregnancy. CoQ10 sits at the center of the mitochondrial energy-production chain and also acts as a fat-soluble antioxidant. The placenta, in particular, is a metabolically intense organ that needs robust mitochondrial function and protection against oxidative damage.
When CoQ10 levels don’t rise as expected, problems may follow. Research has found a correspondence between low CoQ10 levels and spontaneous abortion.3Fetal Diagnosis and Therapy. Coenzyme Q10 in Pregnancy Separately, studies have observed a positive correlation between maternal CoQ10 levels and infant birth weight.4PubMed. Positive correlation between maternal serum coenzyme Q10 levels and infant birth weight These are observational findings — they don’t prove that low CoQ10 causes miscarriage or poor growth — but they fit with the broader picture of CoQ10 as a molecule the body treats as important during pregnancy.
The Preeclampsia Trial
The single most important piece of clinical evidence for CoQ10 supplementation in pregnancy comes from a randomized, placebo-controlled trial in women at risk for preeclampsia. Women began taking CoQ10 at 20 weeks of gestation and continued until delivery.
The results were striking: roughly 14% of women in the CoQ10 group developed preeclampsia, compared with about 26% in the placebo group — a 44% relative reduction in risk.1PubMed. Coenzyme Q10 supplementation during pregnancy reduces the risk of pre-eclampsia The finding was statistically significant and the supplement was well tolerated, with no notable difference in side effects between groups.
This is encouraging, but context matters. It was a single trial of moderate size, conducted in a specific population of women already identified as being at elevated risk. It has not been replicated by an independent group in a large multicenter trial, which is typically what it takes before a finding changes clinical guidelines. Some clinicians discuss CoQ10 with high-risk patients on the strength of this result, but it hasn’t become a standard recommendation.
How CoQ10 Moves Between Mother and Baby
One question that comes up with any supplement taken during pregnancy is whether and how much reaches the fetus. For CoQ10, the answer is nuanced. Maternal blood levels of both ubiquinol and ubiquinone are significantly higher than the levels found in umbilical cord blood.5PubMed. Ubiquinol-10 and ubiquinone-10 levels in umbilical cord blood of healthy foetuses and the venous blood of their mothers This gradient suggests the placenta does not simply pass CoQ10 through freely — the baby’s blood maintains its own, lower concentration.
The placenta itself contains CoQ10, and the levels there change dramatically in complicated pregnancies. In preeclampsia, placental CoQ10 content has been measured at roughly three times the level found in healthy placentas, and cord blood CoQ10 was also considerably higher in preeclamptic pregnancies.6PubMed. Coenzyme Q10 is increased in placenta and cord blood during preeclampsia This initially sounds paradoxical — if CoQ10 is supposed to help, why is there more of it when things go wrong?
The likely explanation is compensatory. Preeclampsia involves significant oxidative stress and mitochondrial dysfunction in the placenta. Research has found substantial drops in mitochondrial DNA copy number and in the activity of key mitochondrial enzymes in preeclamptic placentas, alongside elevated markers of a cellular cleanup process that removes damaged mitochondria.7PubMed Central. Mitochondrial Dysfunction Combined with Elevated CoQ10 Levels Specifically in Placental Cytotrophoblasts Suggests a Role for Mitophagy in Preeclampsia The elevated CoQ10 appears to be the body’s attempt to counteract this mitochondrial damage after the fact. Supplementing with CoQ10 earlier in pregnancy, as the preeclampsia trial did, may work by reinforcing defenses before damage becomes severe rather than relying on the body’s late-stage compensatory response.
What Amniotic Fluid Levels Reveal
An intriguing observation adds complexity to the picture. Researchers measured CoQ10 levels in amniotic fluid during the second trimester and found that levels were significantly higher in pregnancies that later developed fetal growth restriction. At the same time, the antioxidant capacity of the amniotic fluid was lower in those pregnancies. There was also a negative correlation between amniotic CoQ10 and birth weight — higher amniotic CoQ10 was associated with smaller babies.8PubMed Central. Amniotic coenzyme Q10: is it related to pregnancy outcomes?
This does not mean CoQ10 supplementation causes growth restriction. The elevated amniotic CoQ10 likely reflects the same compensatory response seen in preeclamptic placentas: when the feto-placental unit is under oxidative stress, CoQ10 production ramps up as part of the body’s defense. But the finding is a reminder that the relationship between CoQ10 and pregnancy outcomes is not simply “more is always better.” Context and timing matter, which is one reason self-prescribing high doses without medical guidance isn’t ideal, even for a supplement with a mild side-effect profile.
Fertility and Preconception Use
Much of the interest in ubiquinol for reproductive health starts before pregnancy. CoQ10 supplementation has been studied as a way to improve egg quality, particularly in women with diminished ovarian reserve or those undergoing assisted reproduction. The rationale centers on mitochondria: eggs are among the most mitochondria-rich cells in the body, and their energy production declines with age. CoQ10, as the key electron carrier in the mitochondrial chain, is an obvious candidate for support.
Clinical studies have reported that CoQ10 supplementation can improve ovarian function, increase the number of eggs retrieved during fertility procedures, and improve embryo quality, with the most encouraging results in women who are older or who have diminished ovarian reserve.9PubMed Central. Exploring the protective effects of coenzyme Q10 on female fertility CoQ10’s ability to reduce oxidative stress and enhance mitochondrial activity also appears to benefit oocyte maturation and fertilization rates.10PubMed Central. Coenzyme Q10 Stimulate Reproductive Vatality
If you’re already taking ubiquinol for fertility reasons and become pregnant, the transition into pregnancy use is relatively seamless from a safety standpoint. The supplement doesn’t need to be abruptly discontinued, though it’s worth discussing your dose with your healthcare provider since the purpose of supplementation shifts from egg-quality support to general prenatal antioxidant support.
Gestational Diabetes and CoQ10 Status
Researchers have also looked at CoQ10 in the context of gestational diabetes. One study tracked plasma CoQ10 levels in women with gestational diabetes compared to healthy pregnant controls at different points in the third trimester. When adjusted for cholesterol, there was no significant difference between the groups at 28 to 36 weeks. But in late pregnancy, around 36 to 40 weeks, cholesterol-adjusted CoQ10 levels were significantly different between the groups, coinciding with increased insulin resistance and higher oxidative stress markers.11Diabetes Research and Clinical Practice. Plasma coenzyme Q10 is increased during gestational diabetes
This hints that CoQ10 metabolism may be disrupted in gestational diabetes, particularly as pregnancy reaches full term. Whether supplementation could help manage the condition has not been tested in a clinical trial designed for that purpose, so this remains an observation rather than an actionable finding. But it’s one more indication that CoQ10 status is intertwined with metabolic health during pregnancy and may eventually inform future research.
CoQ10 in Breast Milk
For those wondering whether CoQ10 matters after delivery, CoQ10 naturally appears in breast milk but at declining concentrations. Measurements during early lactation show a gradual drop in milk CoQ10 levels over the first weeks postpartum, and when adjusted for the fat content of the milk, this decline becomes even more pronounced.12PubMed. Coenzyme Q10 in maternal plasma and milk throughout early lactation
This pattern likely reflects the changing composition of breast milk as it transitions from colostrum to mature milk, and may also reflect the mother’s own CoQ10 stores redistributing after the demands of pregnancy wind down. Whether supplementation during breastfeeding meaningfully changes the CoQ10 content of milk is unknown — it hasn’t been directly studied. The baby’s own CoQ10 production takes over after birth, so the clinical significance of the declining milk levels remains uncertain.
Practical Dosing Considerations
Most pregnancy-related research has used CoQ10 doses in the range of 100 to 200 mg per day. The preeclampsia trial used 200 mg daily.1PubMed. Coenzyme Q10 supplementation during pregnancy reduces the risk of pre-eclampsia For fertility purposes, doses of 200 to 600 mg per day have been used in various studies, though no single dose has been established as optimal.
Because ubiquinol is substantially more bioavailable than ubiquinone, a lower dose of ubiquinol may achieve similar blood levels to a higher dose of ubiquinone.2PubMed Central. Ubiquinol in Fertility and Reproduction: A Conditionally Essential Nutrient for Critical Early-Life Stages – Section: Bioavailability and Safety If you’re switching between forms based on what’s available or affordable, keep this in mind — you generally need less ubiquinol to reach the same circulating level.
CoQ10 is fat-soluble, so absorption improves when you take it with a meal that includes some fat. Mild stomach discomfort is the most commonly reported side effect, and taking it with food generally helps. One interaction worth knowing about: CoQ10 has a chemical structure similar to vitamin K and may theoretically reduce the effectiveness of warfarin, a blood thinner. This is rarely relevant in pregnancy since warfarin is generally avoided in pregnant women, but if you’re on any anticoagulant therapy, mention your CoQ10 use to your prescriber. There is no established upper limit for CoQ10 during pregnancy from any major regulatory body, though most clinicians who recommend it in pregnancy stay at 200 mg per day or below.