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18 weeks pregnant: what's happening to you and your baby

You're in your second trimester, around 4 months pregnant. How your baby is growing at 18 weeks, what you might be feeling, and what to sort this week.

Katie Manson
October 11, 2026
An expectant couple laughing together
TrimesterSecond
BabyAbout 14.2cm from head to bottom
Countdown22 weeks to go

Your baby at 18 weeks

Hearing, touch, swallowing and sucking reflexes are developing.

Your baby is wriggling and moving their arms and legs.

Your body at 18 weeks

You may feel clumsier, and your breasts may have gone up a size.

Lower blood pressure can make you dizzy if you stand up quickly, and a dark line may appear down your tummy.

Decide together before the scan whether you want to find out the sex, so nobody blurts it out.

Your to-do list at 18 weeks

  • Your anomaly scan will be offered between 18 and 21 weeks. Tell the sonographer beforehand if you don't want to know the sex.
  • Get your maternity exemption certificate sorted if you haven't already.

When to call your midwife

Contact your midwife or maternity unit straight away if you have bleeding, fluid leaking, severe tummy pain, a bad headache with vision problems or swelling, or, once you're feeling them, your baby's movements slow down or stop.

How big is my baby at 18 weeks pregnant?

At 18 weeks, your baby is about 14.2cm from head to bottom.

How many months is 18 weeks pregnant?

18 weeks pregnant is around 4 months, in the second trimester.

What should I do at 18 weeks pregnant?

Your anomaly scan will be offered between 18 and 21 weeks. Tell the sonographer beforehand if you don't want to know the sex.

Keep reading

This guide is general information based on NHS week-by-week guidance, not medical advice. Every pregnancy is different, and baby sizes are averages. If you're worried about anything, contact your midwife, GP or maternity unit. See the NHS week-by-week guide.

If you’re trying to conceive (TTC), you probably know that there are certain foods and nutrients that become especially important once you’re pregnant. But nutrition plays a vital role even when trying to conceive, much like laying a strong foundation before constructing a house.

Certain nutrients create that foundation by supporting egg and sperm health (yes, nutrition matters for both partners), hormone balance and creating a hospitable environment for a fertilized egg to implant. In fact, studies show that certain nutrients can help increase fertility and improve success rates for both natural conception and fertility treatments.

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In other words, nutrition is a key player in the TTC journey, but getting the right nutrients in the right quantities can be tricky. That’s where supplements come in. Just as you’d take a multivitamin to fill in nutritional gaps for optimal health, fertility supplements can give you that extra nutrient boost.

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Choosing supplements for your fertility journey

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When choosing a supplement to support your fertility journey, look for science-backed, high-quality ingredients. Our editors are careful to select and partner with brands that use ingredients that have been clinically studied to support fertility. Eu Natural® (pronounced you) covers all those bases and more. We love knowing that Eu Natural® products contain zero artificial additives, binders, or fillers and are lab-tested to ensure purity and potency.

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Photobook: Luthier. Beeches Lane by &Something

When choosing a supplement to support your fertility journey, look for science-backed, high-quality ingredients. Our editors are careful to select and partner with brands that use ingredients that have been clinically studied to support fertility. Eu Natural® (pronounced you) covers all those bases and more. We love knowing that Eu Natural® products contain zero artificial additives, binders, or fillers and are lab-tested to ensure purity and potency.

Katie Manson