It's not just your belly that changes

The Pregnancy Guide

Nobody really tells you. Not everything.

You read about morning sickness. You hear about labour. But what happens to your skin, breasts and hair during pregnancy and postpartum, and why your body can feel different long after the baby has arrived, is rarely spoken about as openly.

This guide explains what actually happens to the body during pregnancy, in the first weeks after birth, and throughout the first year. Phase by phase, without unnecessary worry, because things are easier to deal with when you understand them.

Sources and a medical note are listed at the bottom of this guide. This guide does not replace medical advice. If you have any concerns, always contact a midwife or doctor.

During Pregnancy

Pregnancy is the body's most comprehensive process of change in adulthood. It happens quickly, it happens everywhere, and it is driven by a hormonal system working harder than ever.

Hormones set everything in motion

Oestrogen can reach up to a thousand times its normal level during pregnancy. Progesterone rises sharply and relaxes the body's muscles and ligaments – which explains fatigue, heartburn and the classic feeling that your body is not quite your own. The hormone relaxin softens the body's joints and connective tissue, not just in the pelvis but throughout the entire body. It is a necessary preparation, but it makes the body more flexible and sensitive than usual.

Skin changes

Hormonal stimulation of pigment cells is noticeable in several ways. The nipples darken early. A darker line may appear along the middle of the abdomen – linea nigra – visible in approximately 64 percent of pregnant women. Brown, symmetrical pigmentation patches on the face, on the cheeks and forehead, are known as the pregnancy mask (chloasma) and affect up to three quarters of all pregnant women. Sunlight intensifies them.

The classic pregnancy glow is not a myth. With 40 to 50 percent more blood in circulation, the skin looks more flushed, and hormonal stimulation provides natural moisture. How noticeable this is varies. Some experience a radiance; others find their skin becomes oilier.

Stretch marks – for most women

Stretch marks form when the skin stretches faster than the underlying fibres can adapt. Between 50 and 90 percent of pregnant women develop them, most often on the abdomen, breasts, thighs and hips. They are a normal part of what the body goes through, and for many women a permanent reminder of what it has carried.

Most stretch marks fade over time, from pink or red to a softer, silvery tone. We cover them in more detail further down in the guide.

What research does show is that changes to the breasts and abdomen during and after pregnancy often affect how clothes and underwear fit long term. Many women find that the bras and styles that worked before pregnancy no longer feel right, not because something is wrong, but because the body has genuinely changed shape.

The bust during pregnancy

Breast tenderness is often the very first sign of pregnancy. Most women notice that their cup size increases by one to two sizes, and the ribcage often widens by a band size. The nipples and areola darken, glandular tissue grows and prepares for milk production. Colostrum begins to be produced as early as weeks 16 to 19. If there is a little leakage in the third trimester, this is completely normal.

The Fourth Trimester – The First Twelve Weeks

It is called the fourth trimester, and rightly so. Recovery after childbirth is not a moment, it is a process. The Swedish health service 1177 Vårdguiden notes that it can take up to a year for the body to recover.

The hormonal cliff

Within 24 to 48 hours of delivering the placenta, oestrogen and progesterone fall by approximately 90 percent. It is the most dramatic hormonal shift in a single moment during a woman's entire life. Night sweats, hot flushes, mood swings and sleep disturbances are direct effects. In many ways, the postpartum hormonal environment resembles the menopause.

The breasts in the first weeks

Around days three to five, the breasts swell significantly as milk production begins. Three in four breastfeeding mothers experience inflammatory breast problems during the first eight weeks. When milk production regulates – usually around six weeks the situation stabilises and the breasts feel softer. This is normal and does not mean the milk has dried up.

Wellbeing, baby blues and more

Half to three quarters of all new mothers experience baby blues: tears, emotional sensitivity and mood swings that begin around days two to three and ease within ten to fourteen days. It is a direct reaction to the hormonal drop and requires no treatment.

Postnatal depression is something different. It affects an estimated one in seven new mothers and involves persistent low mood that impacts daily life. Seek help if you feel unwell for more than a week.

Seek medical attention immediately if you experience:

  • Heavy bleeding or fever above 38°C

  • Severe headache with visual disturbance

  • Pain and swelling in one leg

  • Thoughts of harming yourself or the baby

Hair

Around three to four months postpartum, roughly one third to one half of all new mothers notice more hair falling out – sometimes dramatically more. This is called telogen effluvium. During pregnancy, high oestrogen levels kept more hair strands in the growth phase than usual. Now they shed almost simultaneously. It occurs diffusely, not in patches, and most women regain normal hair volume within six to twelve months.

Stretch marks over time

Red or purple stretch marks gradually fade to silver and skin-tone over six to twenty-four months. They do not disappear, but they fade considerably. Active skin treatments such as tretinoin are best suited after pregnancy and breastfeeding have ended, and it is the only substance with solid clinical evidence for reducing their visibility.

Long recovery – a year and beyond

The six-week check-up is important. But it is not a certificate that the body has fully healed. Recovery continues.

Does breastfeeding affect the bust?

This is one of the most common concerns. Research gives a clear answer: no. A study in the Aesthetic Surgery Journal following 93 mothers showed that breastfeeding was not an independent risk factor for ptosis. What actually affects the shape of the breasts is the number of pregnancies, age, smoking and pre-pregnancy size. Pregnancy itself changes the shape, not breastfeeding.

What may change permanently

Most things return to how they were. But some things remain different, and that is normal. Research shows that 60 to 70 per cent of mothers permanently develop slightly longer or wider feet. The hips may become wider. The consistency and shape of the breasts changes in most women after a pregnancy. This is the body after having done something remarkable.

Not "back" but "forward"

The culture around postpartum is full of phrases about returning to your body, your weight, your shape. But the body does not return to anything. It moves forward and finds a new normal. That deserves respect, not comparison.

Your body has changed – and your underwear should too

Pregnancy changes the body in ways that last beyond the first weeks at home. The breasts shift in size and shape, often more than once, first during pregnancy, then with breastfeeding, and again during weaning. The skin around the abdomen has stretched. The ribcage may have widened slightly. For many women, the underwear that fitted well before pregnancy simply does not feel right anymore, and that is completely normal.

In the short term, comfort is the priority. Soft fabrics without rough seams, a flexible fit that adapts as the body changes, and materials that are gentle on sensitive skin all matter more than they did before.

Longer term, it is worth reassessing fit properly rather than returning to old sizes out of habit. A well-fitting bra makes a real difference when the body has genuinely changed shape.

What to look for when choosing underwear after pregnancy:

  • Prioritise soft, non-irritating fabrics, especially if you are breastfeeding or have sensitive skin

  • Check your bra size again, ideally at three months postpartum and again after weaning

  • Look for flat seams and flexible waistbands in briefs to avoid pressure on the abdomen

  • If you experience night sweats, common in the postpartum period as hormones rebalance, moisture-wicking fabric makes a significant difference

Swegmark's Cool & Dry collection was developed for exactly these moments. The moisture-wicking fabric draws sweat away from the skin quickly, making it as relevant during postpartum hormonal changes as it is during menopause. The entire range is OEKO-TEX® certified, free from harmful substances, which matters when your skin is at its most sensitive.

For everyday wear, our Modal briefs offer something different. Modal is a naturally derived fibre that is exceptionally soft, breathable and gentle against the skin. It drapes rather than clings, making it a comfortable choice as the body continues to settle in the months after birth.

Selected underwear

5 things to keep in mind for the skin you're in

Adjust your bra size regularly. Cup size changes more times during pregnancy and breastfeeding than at any other point in life. Get re-fitted in the second trimester, before birth, and again three to four months after breastfeeding ends.

Choose soft fabrics during pregnancy. Breast tissue is more sensitive than usual. Seamless bralettes and soft constructions without a stiff underwire against the ribcage suit early pregnancy best.

Moisture-wicking fabric makes a real difference postpartum. Night sweats and hormonal fluctuations after birth resemble those of the menopause. Fabrics that draw moisture away from the skin keep you dry and support better sleep.

Pigmentation changes on the face worsen with sun exposure. Broad-spectrum SPF 30+ sunscreen – ideally mineral – is the simplest and most effective way to manage the pregnancy mask.

Seek medical advice if hair loss continues beyond twelve months. Persistent hair loss after a year may indicate thyroid problems or iron deficiency, both straightforward to investigate and treat.

Sources and contact information

This guide is written to give you honest, research-based information about what your body goes through during pregnancy and after birth. It is not a substitute for medical advice. Always speak to your midwife or doctor with questions about your own health.

© Swegmark / Underwear Sweden AB

Contact information

If you are struggling after birth, please reach out. Postnatal depression is common and treatable.

  • Contact your midwife, health visitor or GP as a first step. They can refer you to further support.

  • Mind (UK): www.mind.org.uk, 0300 123 3393

  • PANDAS Foundation (UK): Specialist support for perinatal mental health. www.pandasfoundation.org.uk, 0808 1961 776

  • Samaritans: 116 123, available 24 hours a day. www.samaritans.org

  • Emergency: 999 (UK) / 112 (EU) in immediate danger.

Sources

1177 Vårdguiden, Common discomforts during pregnancy: www.1177.se

1177 Vårdguiden, The body after childbirth: www.1177.se

1177 Vårdguiden, Depression around the time of having a baby: www.1177.se

Rikshandboken i barnhälsovård, Depression in new parents: www.rikshandboken-bhv.se

Brennan M et al. Topical preparations for preventing stretch marks. Cochrane Database, 2012.

Rinker B et al. The effect of breastfeeding on breast aesthetics. Aesthetic Surgery Journal, 2008.

PMC / NIH, Physiology, Postpartum Changes: www.ncbi.nlm.nih.gov

PMC / NIH, Cutaneous Changes During Pregnancy: A Comprehensive Review, 2024.