Glycans in Pregnancy: How Your Sugars Change Through Conception, Pregnancy and Postpartum

Pregnancy is not a single event for the immune system; it is a journey. From the moment of conception through the months after birth, the sugar structures attached to antibodies, known as glycans, shift in a predictable sequence, and each shift leaves a mark on biological age. This is the same biology that a glycan-based biological age test is built to measure, and pregnancy is one of the clearest, fastest examples of it in action. Whether you are trying to understand your own results or explaining them to a patient, the nine months of pregnancy work like a compressed, natural experiment in how quickly biological age can move.

Most explanations of pregnancy and the immune system stop at a single milestone: the relief that some autoimmune conditions bring during the second and third trimesters. That milestone is real and well studied, but it is one stop on a longer route. The fuller picture runs from the glycan changes already happening before conception, through the mechanics of fertilisation itself, across each trimester, and into the months after birth when the pattern reverses. Mapped out stage by stage, it becomes a roadmap for understanding how biological age moves throughout pregnancy and why the shifts are temporary rather than permanent.

For a fuller grounding in what glycans are and how they work before diving into the pregnancy timeline, Glycans: The Sugars That Reveal Your Biological Age and Immune Health covers the basics this roadmap builds on.

Before conception: the glycan baseline

Even before pregnancy begins, glycans are already moving in step with a woman's hormones. A study following 70 healthy women across three menstrual cycles, sampling every 7 days, found that antibody glycans shift in a cyclic pattern alongside estrogen and progesterone. The follicular phase favours glycan structures linked to a more pro-inflammatory profile, while the period after ovulation favours the anti-inflammatory Glycan Youth and Glycan Shield indexes. These swings are real, but small, averaging little more than one percent, and they are not large enough to move the overall GlycanAge score. A GlycanAge test can be taken on any day of the menstrual cycle. However, for more consistent comparisons over time, it's best to test at a similar point in each cycle.

Conception: how sugars guide sperm and egg

Glycans are involved even earlier than hormones suggest. Mammalian sperm cells travel through the female reproductive tract coated in sialic acid sugars, a glycan disguise that helps them avoid being attacked as foreign cells by the woman's immune system. During capacitation, the final maturation step before fertilisation, sperm shed part of this sialic acid coating through the activity of their own sialidase enzymes, a change that is necessary for sperm to bind and recognise the egg's outer layer. The same glycan logic that helps a fertilised egg implant without triggering immune rejection is, a few weeks later, the logic behind why autoimmune symptoms can ease during pregnancy.

The three trimesters of glycans

Once pregnancy is established, a woman's immune system adapts to accommodate the baby's presence throughout the body, changing its normal defences to avoid rejecting foetal tissue. In fact, some pregnancy losses happen because this immune adaptation fails. The adaptation also makes a pregnant woman more prone to infections, which is why most pregnancy diets avoid food that can be colonised by harmful bacteria, such as cured meat and raw eggs. It has upsides too. As pregnancy progresses through each trimester, rising estradiol drives changes in antibody glycosylation, including increased galactosylation and sialylation, reflected in the anti-inflammatory Glycan Youth and Glycan Shield indexes. This antibody remodelling builds gradually through the first and second trimesters and reaches its peak in the third, which is when its anti-inflammatory effects are strongest. Each trimester therefore represents a distinct point on the glycan timeline rather than one uniform state, with the immune system, and the biological age readout it produces, looking measurably different at the start of pregnancy than at the end of it.

Pregnancy already complicates clinical decision-making well beyond glycans, which is part of why an objective marker matters so much here.

"We're faced with making treatment decisions for pregnant patients with very limited evidence for efficacy and safety, and sometimes there's a real reluctance to prescribe, which means the care we can offer is affected."

 — Dr. Alka Patel, GP, Lifestyle Medicine Doctor, Author and Podcaster

The autoimmune milestone

The clearest evidence of this trimester-by-trimester shift comes from women with rheumatoid arthritis, a disease in which antibodies mistakenly attack the joints, causing chronic swelling, inflammation, and pain. From the literature, we know that low-galactosylation glycans associate with future rheumatoid arthritis risk, and that disease activity usually improves during pregnancy. Researchers at Erasmus MC in Rotterdam tracked antibody glycosylation in pregnant women, healthy and diseased, and found that all of them experienced the same natural rise in antibody galactose. In women with rheumatoid arthritis, that rise tracked closely with symptom relief: by the third trimester, their galactose levels resembled those of healthy pregnant women, and many felt their disease had gone quiet.

The biological age shift

This is more than a curiosity about one disease. Glycan Youth and Glycan Shield are the same anti-inflammatory indexes that feed into a woman's GlycanAge score, so the rise in antibody galactose during pregnancy shows up as a temporary fall in biological age. Research on estradiol and biological age found that suppressing estrogen raised glycan-based biological age by a median of 9.1 years, an effect fully reversed by estradiol supplementation. That particular study induced a temporary, menopause-like hormone state rather than studying postpartum women directly, but it demonstrates how strongly, and how reversibly, estrogen drives this specific biological age marker.

"We did a study on sex hormones and glycans with a group in the US, in women with chemically induced menopause and in men with chemical blockage of hormone production. When you block the hormones, either estrogen or testosterone, IgG glycosylation changes rapidly, and people age up to ten to twenty years in a couple of months. If you restore the hormones, this does not happen. In our randomised, placebo-controlled study, only the women who received the estrogen patch were protected from this increased glycan ageing."

 — Prof. Gordan Lauc, Professor of Biochemistry and Molecular Biology, University of Zagreb, and Co-Founder & Chief Scientific Officer, GlycanAge

Pregnancy is essentially a natural version of the same hormone-driven effect, playing out over nine months instead of a clinical trial, and it is one of the few times biological age can fall this much without any deliberate intervention at all.

The postpartum glycan crash

The fall does not last. In a study of 148 women with rheumatoid arthritis followed from before conception to six months postpartum, Glycan Youth and Glycan Shield rose steadily through pregnancy and then dropped sharply after birth, reaching their lowest point around six months postpartum, the same window in which disease flares became more common. For most women, this postpartum dip is a hormone-driven rebound rather than a sign that anything has gone wrong, but it is exactly why postpartum biological age deserves as much attention as the pregnancy itself, particularly for anyone whose symptoms quietly returned a few months after delivery.

Reading your own roadmap

Pregnancy compresses a hormone-driven biological age cycle into less than a year, which makes it one of the clearest windows into how responsive glycans really are. The same pathways are at work at every other hormonal turning point in life, from the menstrual cycle to hormone therapy to natural ageing. For clinicians managing patients with autoimmune conditions, this roadmap is a reminder that inflammaging deserves an objective marker rather than a symptom checklist alone, especially across a pregnancy and postpartum timeline where symptoms can be misleading.

"Asking about a woman's pregnancy history is now recognised as important for assessing future cardiovascular risk. Pregnancy history can give us a glimpse of a woman's future health."

— Prof. Samia Mora, Associate Professor of Medicine, Harvard Medical School; Brigham and Women's Hospital

For anyone curious about their own glycan-driven biological age, a finger-prick GlycanAge test, with results in two to three weeks, can be ordered from the shop before conception, during pregnancy, or postpartum, to see exactly where on this roadmap the immune system currently sits.

External sources

• Jurić J, Peng H, Song M, Vučković F, Šimunović J, Trbojević-Akmačić I, et al. Periodic changes in the N-glycosylation of immunoglobulin G during the menstrual cycle. Engineering. 2023;26(7):108-118. Link: https://doi.org/10.1016/j.eng.2022.10.020

• Ma F, Wu D, Deng L, Secrest P, Zhao J, Varki N, et al. Sialidases on mammalian sperm mediate deciduous sialylation during capacitation. J Biol Chem. 2012;287(45):38073-38079. Link: https://pubmed.ncbi.nlm.nih.gov/22989879/

• Gudelj I, Salo PP, Trbojević-Akmačić I, Albers M, Primorac D, Perola M, et al. Low galactosylation of IgG associates with higher risk for future diagnosis of rheumatoid arthritis. Biochim Biophys Acta Mol Basis Dis. 2018;1864(6):2034-2039. Link: https://pubmed.ncbi.nlm.nih.gov/29572115/

• Ince-Askan H, Dolhain RJEM. Pregnancy and rheumatoid arthritis. Best Pract Res Clin Rheumatol. 2015;29(4-5):580-596. Link: https://pubmed.ncbi.nlm.nih.gov/26697768/

• Bondt A, Selman MHJ, Deelder AM, Hazes JMW, Willemsen SP, Wuhrer M, et al. Association between galactosylation of immunoglobulin G and improvement of rheumatoid arthritis during pregnancy is independent of sialylation. J Proteome Res. 2013;12(10):4522-4531. Link: https://pubmed.ncbi.nlm.nih.gov/24016253/

• Jurić J, Kohrt WM, Kifer D, Gavin KM, Pezer M, Nigrovic PA, et al. Effects of estradiol on biological age measured using the glycan age index. Aging (Albany NY). 2020;12(19):19756-19765. PMC: https://pmc.ncbi.nlm.nih.gov/articles/PMC7732334/

• van de Geijn FE, Wuhrer M, Selman MHJ, Willemsen SP, de Man YA, Deelder AM, et al. Immunoglobulin G galactosylation and sialylation are associated with pregnancy-induced improvement of rheumatoid arthritis and the postpartum flare: results from a large prospective cohort study. Arthritis Res Ther. 2009;11(6):R193. PMC: https://pmc.ncbi.nlm.nih.gov/articles/PMC3003510/