Pregnancy Calculator Baby Centre UK

This pregnancy calculator helps you track your pregnancy week by week, calculate your due date, and understand your baby's development. Whether you're trying to conceive or already pregnant, this tool provides essential information for UK parents-to-be.

How to Use This Calculator

To get the most accurate results, you'll need to know either your last menstrual period (LMP) date or your estimated due date (EDD). The calculator will then show you:

Your current pregnancy week
Your estimated due date
Your baby's development stage
A visual timeline of your pregnancy

Note: The average pregnancy lasts 40 weeks (280 days) from the first day of your last menstrual period. However, every pregnancy is unique, and your due date may vary.

Example Calculation

If your last menstrual period was on January 1, 2023, your estimated due date would be October 31, 2023. If today is May 1, 2023, you would be in your 16th week of pregnancy.

Due Date = Last Menstrual Period + 280 days Pregnancy Week = (Current Date - Last Menstrual Period) / 7

Understanding Pregnancy Weeks

Pregnancy is divided into three trimesters, each lasting about 13 weeks:

First Trimester (Weeks 1-12): The foundation of your baby is formed. You may experience morning sickness, fatigue, and frequent urination.
Second Trimester (Weeks 13-28): Your baby grows rapidly, and you may notice your bump. This is often the most comfortable time of pregnancy.
Third Trimester (Weeks 29-40): Your baby prepares for birth, and you may experience Braxton Hicks contractions, back pain, and shortness of breath.

Week Range	Key Developments
1-4	Implantation, early organ formation
5-8	Facial features develop, limbs form
9-12	Baby can hear, fingers and toes form
13-28	Rapid growth, baby gains weight and muscle
29-40	Baby's lungs mature, fat stores build

Baby Development Timeline

Each week of pregnancy brings new developments. Here's a quick overview:

First Trimester (Weeks 1-12)

Week 1: Implantation, early cell division
Week 4: Heart begins to beat
Week 8: Limbs and digits form
Week 12: Baby can hear sounds, eyes can detect light

Second Trimester (Weeks 13-28)

Week 16: Baby can suck its thumb
Week 20: Baby's bones are mostly formed
Week 24: Baby can taste, hears mother's voice
Week 28: Baby's lungs are nearly mature

Third Trimester (Weeks 29-40)

Week 32: Baby gains most weight
Week 36: Baby's head engages in the pelvis
Week 38: Baby is considered full-term

Common Questions About Pregnancy

Here are answers to some frequently asked questions about pregnancy:

How many weeks is a full-term pregnancy?

A full-term pregnancy is typically 38-42 weeks (266-300 days) from the first day of the last menstrual period. In the UK, a baby born between 37 and 42 weeks is considered full-term.

What is the average due date?

The average due date is calculated by adding 280 days (40 weeks) to the first day of your last menstrual period. For example, if your LMP was January 1, your due date would be October 31.

When should I see a doctor during pregnancy?

You should see your healthcare provider at your first prenatal visit between 8 and 12 weeks. Regular checkups are recommended every 4 weeks until 28 weeks, then every 2 weeks until delivery.

What is the difference between LMP and EDD?

LMP (Last Menstrual Period) is the first day of your last menstrual period. EDD (Estimated Due Date) is calculated by adding 280 days to your LMP. Some women use ultrasound dates for more accuracy.