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Your body after birth: weight, breastfeeding and the jabs

Your body has done something huge. There is no deadline for getting your old shape back, and the NHS does not set one. Here is what the guidance does say.

By Sian Anderson. Published 5 November 2026. 7 minute read. Information, not medical advice.

Sian Anderson, Writer and editor, MyGLP. Sources checked 5 November 2026.

What changes in the first weeks

After the birth your joints and ligaments stay looser for a few months. The NHS guide to exercise after having a baby warns against overstretching and twisting for this reason. Your tummy muscles, pelvic floor and sleep all need time. None of this is a failure. It is the normal recovery from pregnancy and birth.

NICE guidance on weight management before, during and after pregnancy tells health professionals to give women a realistic picture of how long it takes to lose the weight gained in pregnancy. It also says advice should fit your life: a new baby, tiredness, and problems such as a weak pelvic floor or back pain.

Weight loss medicines while breastfeeding

The weight loss medicines are not used while you breastfeed. The table shows what each source says.

The Mounjaro leaflet and the NHS page word this differently. Both tell you to put the question to a doctor first. Answer the breastfeeding question on any consultation form honestly.
Medicine	What the source says on breastfeeding
Mounjaro (tirzepatide)	The NHS tirzepatide page says it is not used while breastfeeding, as it is not known if it passes into milk. The Mounjaro leaflet says it passes into milk in very low amounts and is not expected to be absorbed by a baby, and tells you to talk to your doctor before using it
Wegovy injection	The Wegovy pen leaflet says you should not use it if you are breastfeeding, as it is unknown if it passes into milk
Wegovy pill	The Wegovy tablets leaflet says do not use it if you are breastfeeding
Foundayo	Check the leaflet and ask the prescriber before you use it

If you are not breastfeeding, a weight loss medicine is still a decision for after your recovery, with a prescriber who knows you have had a baby. Your appetite, sleep and mood are all settling. Our fertility and pregnancy guide covers planning a restart.

Losing weight while you breastfeed

You do not need a special diet to breastfeed. The NHS breastfeeding diet page recommends a healthy, varied diet, with at least 2 portions of fish a week (no more than 2 of oily fish) and no more than 200mg of caffeine a day. That is about two mugs of coffee.

If you want to lose weight, NICE says a healthy diet, regular moderate activity and gradual weight loss will not affect your ability to breastfeed or the amount or quality of your milk. The NHS gives a practical target: a balanced diet and a 30-minute brisk walk each day. Neither the NHS nor NICE sets a number of kilos a week. Gradual is the word both use, so crash diets and meal replacement shakes are not the plan here.

Take 10 micrograms of vitamin D a day while breastfeeding, the NHS advises. If your baby has only breast milk, they need their own daily vitamin D drops of 8.5 to 10 micrograms, per the NHS breastfeeding vitamins page. Your health visitor can advise.

Tummy muscle separation

During pregnancy the two long muscles down the front of your tummy can move apart along the centre line. This is called diastasis recti. Leeds Teaching Hospitals NHS pelvic health physiotherapists say a small gap after birth is normal and for most women it improves within 8 weeks. Up to a third of women still have a gap at 12 months.

After 8 weeks, a gap wider than two fingers at the belly button, with a bulge when you sit up from lying down, points to diastasis.
Roll onto your side to get in and out of bed, and push up with your arms.
Avoid sit-ups and any exercise that makes your tummy dome or bulge.
Avoid straining on the toilet. Our fibre guide helps with constipation.
If the gap has not closed by 8 weeks, ask your GP to refer you to pelvic health physiotherapy.

Getting moving again

After a straightforward birth you can start walking, gentle stretches and pelvic floor exercises as soon as you feel up to it, the NHS says. Wait for your 6 week check before high-impact exercise such as running or aerobics. Wait until 7 days after your bleeding has stopped before you swim. After a caesarean or a complicated birth, recovery takes longer, so ask your midwife, health visitor or GP before anything strenuous.

The 6 to 8 week check

You should be offered a postnatal check with a GP around 6 to 8 weeks after the birth. The NHS postnatal check page says it covers:

How you are feeling, including your mental health.
Contraception, and which methods suit you now.
An examination if you had stitches, a caesarean, or still have pain after a vaginal birth.
Your blood pressure, if you had problems with it in pregnancy or soon after.
Your weight, if you are overweight, with advice on losing it if you want.

If you were due cervical screening while pregnant, it should be moved to 12 weeks after the birth. NICE says the check is also the time to raise weight if you want to, and that you can ask for a follow-up within 6 months. This appointment is for you, separate from your baby's check. If it feels rushed, ask for a second appointment.

If you feel unwell in the weeks after the birth, contact your midwife, health visitor, GP or 111 the same day. Call 999 in an emergency. Tell someone straight away if you have thoughts of harming yourself or your baby.

Mood, sleep and food

Broken sleep pushes appetite up. Low mood can change how you eat. Neither is a willpower problem. If you feel low, anxious or not yourself, tell your GP or health visitor. The 6 to 8 week check asks about this for a reason. Our sleep guide covers the link between sleep and weight. If you have an autoimmune condition, tell your team about any flare after the birth. Our autoimmune guide explains why the months after birth matter.

Paying for your own medicine? The lowest first-order prices today, with delivery included: Mounjaro from £89.00, Wegovy from £44.00, Wegovy pill from £52.99, Foundayo from £49.00.

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Sources

Keeping fit and healthy with a baby (NHS)
Weight management before, during and after pregnancy (PH27) (NICE)
Tirzepatide: pregnancy and breastfeeding (NHS)
Mounjaro KwikPen patient information leaflet (Eli Lilly, via the electronic medicines compendium)
Wegovy pre-filled pen patient information leaflet (Novo Nordisk, via the electronic medicines compendium)
Wegovy tablets patient information leaflet (Novo Nordisk, via the electronic medicines compendium)
Breastfeeding and diet (NHS)
Breastfeeding vitamins (NHS)
Diastasis of recti (separation of stomach muscles) (Leeds Teaching Hospitals NHS Trust)
Your 6-week postnatal check (NHS)

Sian Anderson

Sian writes the health and nutrition guides on MyGLP. Every clinical claim links to the NHS, NICE, a medical royal college, a regulator or a peer-reviewed paper, and the pages carry no medical advice.

Questions

Can I take Mounjaro while breastfeeding?

The NHS says tirzepatide is not used while breastfeeding. The Mounjaro leaflet says it passes into milk in very low amounts and tells you to talk to your doctor before using it. Raise it with your GP or prescriber first.

Can I take Wegovy while breastfeeding?

No. Both the Wegovy pen leaflet and the Wegovy tablets leaflet say not to use it while breastfeeding. The pen leaflet adds that it is not known whether semaglutide passes into breast milk. Talk to your GP about timing a start for after you stop feeding.

How fast can I lose weight after having a baby?

Neither the NHS nor NICE sets a weekly target. NICE says gradual weight loss with a healthy diet and moderate activity will not affect your milk. The NHS suggests a balanced diet and a daily 30-minute brisk walk.

When can I start exercising after giving birth?

After a straightforward birth, walking, gentle stretches and pelvic floor exercises as soon as you feel up to it. Wait for your 6 week check before running or other high-impact exercise. After a caesarean, ask your midwife or GP first.

Will my tummy muscles go back together?

For most women the gap improves within 8 weeks of birth. Up to a third still have a gap at 12 months. If a bulge remains after 8 weeks, ask your GP for a pelvic health physio referral.