Key Takeaways

• Low-dose NMN restores fertility in aged mice: Four weeks of 0.5 g/L NMN in drinking water increased live-birth rates from 25% to 75%, matching the success observed in SIRT2-boosted animals.
• Egg cells, not whole ovaries, run short on NAD⁺: Oocyte NAD(P)H levels decline with age, leading to spindle errors and poor embryo development; NMN replenishes that pool and normalizes egg structure.
• Less is more: The 0.5 g/L dose outperformed the 2 g/L dose; excess NMN likely breaks down to nicotinamide, which can blunt fertility. Precision dosing is both safer and cheaper.

Overview

Women’s fertility starts to decline well before the rest of the body feels old. A simple drop in NAD⁺ inside the egg cell can push a woman’s biological clock forward years ahead of schedule. 

New animal data show that topping up those dwindling molecules (NAD) with low-dose NMN may restore egg quality and boost live-birth rates. Low-dose NMN has tripled live-birth rates in aged mice, hinting that topping up NAD⁺ might one day protect female fertility. 

However, the research is still in clinical trials, and it may be too soon to say anything certain until human trials confirm the findings. Here is what the science tells us so far, and how it may impact anyone trying to conceive in their mid-forties.

Why NAD⁺ matters for female fertility?

Egg cells burn through NAD⁺ with age. Several studies on animals showed efficacy; however, human trials on pregnant women have not been conducted yet. For example, in one study on mice, oocyte NAD(P)H levels drop sharply, even while the rest of the ovary appears normal. That decline shows up as spindle defects, chromosomal errors, and poor embryo growth, all classic hallmarks of age-related infertility. Researchers wondered if replenishing the lost NAD⁺ could reverse the aging process. They treated 13-month-old mice (roughly equivalent to mid-40s in human terms) with nicotinamide mononucleotide (NMN) in their drinking water for just four weeks. They linked the dip in NAD⁺ to three practical problems:

1. Lower egg yield: Aged mice produced fewer mature oocytes during hormone stimulation.
2. Weaker embryo quality: Faulty spindles led to more chromosomal errors, resulting in slower or stalled embryo development. 
3. Reduced live-birth rates: Only about one in four aged females carried a pregnancy to term versus three in four when NAD⁺ was restored genetically or by NMN. 

Collectively, these findings suggest that NMN may play a role in fertility. They indicate that precise, low-dose supplementation could one day help women in their mid-40s maintain egg quality, support IVF cycles, and even extend the fertile window, without the cost or safety worries of megadosing. 

In short, NAD⁺ acts as an energy and repair currency for egg cells. When the balance runs low, fertility falls, which is why any safe way to refill that pool, such as low-dose NMN, is drawing intense interest.

How aging drains NAD⁺ inside oocytes?

As mice, and by extension women, move past their reproductive prime, the NAD⁺/NAD(P)H pool inside the egg itself collapses, even though the rest of the ovary holds steady. Why does that shortfall hurt? Here’s why:

• NAD(P)H collapse is oocyte-specific: Hyperspectral microscopy revealed a steep drop in intracellular NAD(P)H between young (4–5 wk) and aged (12 mo) mouse oocytes. Supplementing aged animals with low-dose NMN (0.5 g/L in drinking water) for 4 weeks restored the deficit to youthful levels. 
• The rest of the ovary is spared: Mass-spectrometry profiling showed that total NAD(H) in whole-ovary homogenates remains unchanged from 1 to 14 months. The data pinpoint the oocyte as the metabolically vulnerable cell type within the ovarian niche.
• NMN quickly replenishes systemic stores: After oral or drinking-water administration, NMN elevates ovarian NAD⁺ within hours, confirming efficient uptake and biosynthetic conversion in vivo.

Together, these findings establish that a localized energy-cofactor deficit inside oocytes drives reproductive aging, not a whole-tissue shortfall, and that targeted, low-dose NMN can correct it.

Low-dose NMN reverses egg decline in mice

A four-week sip of NMN-fortified water was enough to reboot fertility in middle-aged mice:

• Egg yield bounced back: Aged females given NMN produced as many mature oocytes as young controls and showed far fewer spindle defects. The rescue was evident at a concentration of 0.5 g/L in drinking water.
• Live-birth success tripled: Only 25% of untreated 14-month-old mice delivered pups, but about 75% did so after receiving the low dose. Notably, the higher 2 g/L dose improved egg quality but compromised overall fertility, confirming that less is often more.
• Why lower wins: Researchers suspect excess NMN degrades to nicotinamide, a sirtuin inhibitor that can blunt reproductive gains. However, further research is still needed to confirm this.

Together, these data show that precision, not megadosing, turned back the reproductive clock, a finding that could translate into safer, cheaper supplement strategies for women in their mid-40s.

From mice to women: What we know and don’t

Early human research is thin, but three signposts help frame expectations:

• Safety looks reassuring so far: About a dozen short-term studies have given healthy adults 250-1,000 mg of oral NMN per day for up to three months. No serious side effects have been reported, and routine blood work has stayed within normal ranges. Long-term data, especially in women of reproductive age or during pregnancy, have yet to appear.
• First fertility trials are underway: Two registered clinical studies (1, 2) are now recruiting women with diminished ovarian reserve. Both use oral NMN (daily totals roughly matching the low-dose range that helped mice) and will track embryo quality and pregnancy outcomes. Results are expected after 2026, so firm clinical guidance is still a few years off.
• Preclinical evidence keeps stacking up: Independent mouse experiments, including the low-dose study summarised here, consistently show that topping up NAD⁺ restores spindle integrity, boosts egg yield, and triples live-birth success in aged females.

Note: For women over 40, preliminary studies suggest that NMN is safe, and animal data are compelling; however, using it to improve fertility remains experimental. Anyone considering NMN, especially if pregnant or undergoing IVF, should discuss the idea with a fertility specialist until human trial results arrive because we don’t know the translatability of animal research to humans yet.

Safety concerns: NAD⁺ supplements and pregnancy

• Short-term trials look safe, but pregnancy data are scarce: Human studies have given healthy adults 250 – 1,250 mg of oral NMN per day for up to 12 weeks without serious side-effects or abnormal lab results. In a dose-escalation study, even 1,250 mg daily was well-tolerated by both men and women. Another multicentre trial found no adverse events at 300–900 mg per day and confirmed a dose-dependent rise in blood NAD⁺. 
• Animal work offers cautious optimism: Pregnant rodents given NMN or its sister precursor NR showed normal gestation and, in some models, healthier fetuses under stress conditions such as hypoxia. Animal trials on mice also report that nicotinamide (vitamin B3) can reduce miscarriage and pre-eclampsia-like symptoms. 
• The big gap: human pregnancy trials: No peer-reviewed study has yet tested NMN or NR in pregnant women. Regulatory agencies, therefore, list both compounds as “insufficient data” for use during pregnancy. Until trial reports are available, most clinicians advise caution.

Success stories and early clinical signals

A few human hints are beginning to emerge, although none have yet reached full clinical-trial proof.

• Human-oocyte meta-omics (Human Reproduction, 2025): A UCL team pooled seven NMN studies and analyzed single-oocyte RNA-seq data from women aged 38 years or older. They found depleted NAD-biosynthesis transcripts in low-quality eggs and predicted that NMN supplementation could rescue meiotic competence. No supplementation trial has yet been conducted, but it’s the first human-cell insight to support the mouse work.
• Lab-bench embryos. A poster at the 2024 Human Reproduction meeting reported that adding NMN to discarded oocytes from women of advanced maternal age boosted nuclear maturation and modestly improved cytoplasmic competence.
• Media-covered case report. A 2025 PopSugar feature followed a 40-year-old with repeated IVF failure who tried a short course of NAD⁺ IV infusions. Her antral-follicle count rose, and she later conceived naturally; clinicians quoted in the piece called the outcome “encouraging but anecdotal”.
• NR pilot data. Two small in vitro studies found that nicotinamide riboside, a precursor to NMN, reduced oxidative stress and chromosomal errors in aged human oocytes and improved blastocyst rates in mouse IVF models.

These scattered signals don’t replace the need for controlled trials, but they support the idea that restoring NAD⁺ could translate from mice to the clinic, especially for women over 35 who struggle with egg quality.

Practical guide: science-backed dosing & lifestyle stack

Aged mice regained youthful fertility on just 0.5 g/L of NMN in their drinking water for four weeks; the higher 2g/L dose improved egg quality but reduced overall pregnancy success, likely because excess NMN breaks down into nicotinamide, a sirtuin blocker. Translating mouse water doses to people isn’t exact. Still, pharmacologists place the human-equivalent sweet spot around 250–500 mg of oral NMN per day, the same range used safely in metabolic trials so far.

Suggested starting plan (for women 30+ who are not pregnant):

• NMN capsule, 250 mg once daily with breakfast. Track for eight weeks; if well-tolerated and no gastrointestinal upset occurs, consider 500 mg, pending clinician approval.
• Core lifestyle stack to boost egg health:
• Move most days. Aim for 150 min weekly brisk walking or cycling.
• Eat a Mediterranean plate. Plants, olive oil, fish, beans, berries.
• Sleep 7–9 h. Treat chronic insomnia early.
• Stay cognitively and socially active. Puzzles, language apps, and regular meet-ups.
• Quit tobacco and limit alcohol. Both age ovaries and raise miscarriage risk.

For women who are pregnant or planning IVF:

Speak with your fertility specialist before adding NMN. No human pregnancy data are out yet, so the supplement is still considered experimental during gestation.

Low-dose NMN, combined with everyday healthy habits, is the science-aligned path; megadosing adds cost and may blunt the very gains you’re after.

The dose discovery: Why less is more

Early NMN studies employed high concentrations, assuming that more NAD⁺ would always be beneficial. The researchers later on tested that idea head-to-head and got a surprise:

NMN dose (drinking water, 4 wk)	Live-birth outcome in aged mice	Likely reason for the difference	Take-home
0.5 g/L (low dose)	The highest proportion of females achieved pregnancy and live birth; the time to first litter improved	Replenishes oocyte NAD⁺ without excess nicotinamide buildup	Sweet-spot dose for fertility gains
2 g/L (high dose)	Improved egg quality, but overall fertility lagged behind the low dose	Extra NMN degrades to nicotinamide, a sirtuin inhibitor that can blunt reproduction	“More” can backfire; precision beats megadosing

A lower, precise dose not only works better but also avoids the potential downsides of nicotinamide overload, which is good news for both safety and supplement cost.

Bottom line

Studies on mice have shown that age-related declines in NAD⁺ within egg cells drive most of the fertility decline. Four weeks of low-dose NMN topped up that deficit, restored egg quality, and tripled live-birth success, proof that precision dosing may one day push back the reproductive clock in women. Human trials are ongoing, but until the results are available, NMN remains an experimental add-on.

Frequently asked questions (FAQs)

1. Is NAD⁺ safe during pregnancy?

We don’t have enough human data. Animal studies appear reassuring, but doctors still recommend avoiding NAD⁺ boosters until the clinical trials are completed.

2. Can I take NAD⁺ or NMN while pregnant?

Speak with your obstetrician first. At present, NMN and NR are considered experimental in pregnancy, and routine prenatal vitamins already supply the lower, proven-safe form—niacin.

3. Is NMN use safe when trying to conceive?

Short-term NMN (250–500 mg day⁻¹) appears safe in healthy adults, but its impact on egg quality in humans is still under study. Couples should discuss any supplement plan with a fertility specialist.

4. What does “NMN fertility” mean?

It refers to using the NAD⁺ precursor nicotinamide mononucleotide to restore egg quality and fertility as we age. In mice, NMN rejuvenated oocytes and boosted pregnancy rates.

References

1. Miao Y, Cui Z, Gao Q, Rui R, Xiong B. Nicotinamide Mononucleotide Supplementation Reverses the Declining Quality of Maternally Aged Oocytes. Cell Rep. 2020 Aug 4;32(5):107987. doi: 10.1016/j.celrep.2020.107987. PMID: 32755581.
2. Yi, L., Maier, A. B., Tao, R., Lin, Z., Vaidya, A., Pendse, S., Thasma, S., Andhalkar, N., Avhad, G., & Kumbhar, V. (2023). The efficacy and safety of β-nicotinamide mononucleotide (NMN) supplementation in healthy middle-aged adults: a randomized, multicenter, double-blind, placebo-controlled, parallel-group, dose-dependent clinical trial. GeroScience, 45(1), 29–43. https://doi.org/10.1007/s11357-022-00705-1
3. Li T, Wang Y, Yu Y, Pei W, Fu L, Jin D, Qiao J. The NAD+ precursor nicotinamide riboside protects against postovulatory aging in vitro. J Assist Reprod Genet. 2024 Dec;41(12):3477-3489. doi: 10.1007/s10815-024-03263-x. Epub 2024 Oct 26. PMID: 39460833; PMCID: PMC11707114. 
4. Zhu, Z., Lei, M., Guo, R., Xu, Y., Zhao, Y., Wei, C., Yang, Q., & Sun, Y. (2025). Nicotinamide riboside supplementation ameliorates ovarian dysfunction in a PCOS mouse model. Journal of ovarian research, 18(1), 9. https://doi.org/10.1186/s13048-025-01596-4