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Morning Sickness vs Stomach Bug: Complete UK Guide

Telling Two Common Causes of Sickness Apart

When you are pregnant and suddenly feeling sick, it can be hard to know whether it is just morning sickness or whether you have picked up a stomach bug. The two share many symptoms - nausea, vomiting, and feeling generally unwell - but they have different causes and need different responses.

Understanding the difference matters because a stomach bug can lead to dehydration more quickly in pregnancy and may need extra support.

Typical Features of Morning Sickness

Morning sickness in pregnancy tends to follow a recognisable pattern:

  • Begins around week 6 and eases by week 12 to 14
  • Comes and goes, often without a clear trigger
  • Usually worst in the morning or when hungry
  • Accompanied by other pregnancy signs such as tender breasts, tiredness, and heightened smell
  • Rarely causes a high temperature
  • Rarely causes diarrhoea
  • Gradually builds and then gradually fades over weeks

Morning sickness is driven by hormones and persists for weeks, not days.

Typical Features of a Stomach Bug

A stomach bug (gastroenteritis) is usually caused by a viral or bacterial infection. Common features include:

  • Starts suddenly, often within hours
  • Often accompanied by diarrhoea as well as vomiting
  • May include a high temperature, headache, or aching muscles
  • Usually lasts 24 to 72 hours and then improves
  • Can affect anyone in the household, not just you
  • May follow eating something that was off or being near someone else who was ill

A stomach bug tends to be intense for a short period, then resolves.

Key Differences at a Glance

  • Onset: morning sickness builds gradually; a stomach bug comes on suddenly
  • Duration: morning sickness lasts weeks; a stomach bug usually lasts days
  • Diarrhoea: uncommon in morning sickness, common in a stomach bug
  • Fever: rare in morning sickness, common with a bug
  • Other people ill: a bug may affect family members; morning sickness only affects you
  • Other pregnancy signs: morning sickness often comes alongside tender breasts and tiredness

What to Do for Each

For Morning Sickness

  • Eat small, frequent, bland meals
  • Sip fluids steadily
  • Try ginger, acupressure bands, and rest
  • Mention it at your next midwife appointment unless it is severe

For a Stomach Bug

  • Focus on hydration - sip water, clear soups, or oral rehydration salts
  • Eat only bland foods if you are hungry, such as toast or rice
  • Rest and avoid contact with others where possible
  • Wash your hands thoroughly to avoid spreading the bug
  • Contact your GP or NHS 111 for advice

When to Seek Urgent Help

In pregnancy, any of the following warrant a call to your midwife, GP, or NHS 111:

  • You cannot keep fluids down for 12 to 24 hours
  • You have a high temperature
  • You have severe abdominal pain
  • You see blood in your vomit or stool
  • You feel dizzy, faint, or very weak
  • You have not urinated for many hours
  • Your baby movements have changed (later in pregnancy)

Dehydration can come on faster in pregnancy, so it is better to ask for advice early rather than wait.

A Reassuring Summary

Most of the time, sickness in pregnancy is just morning sickness doing its usual thing. But if your symptoms came on suddenly, involve diarrhoea or fever, or are stopping you from drinking anything, it may be a stomach bug and it is worth checking in with a healthcare professional. Either way, help is available, and staying hydrated is the most important priority.