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Am I Pregnant? / Pregnancy / Smartmum

Pregnancy Calculator: How Pregnant Am I?

Pregnancy Calculator: How Pregnant Am I?

Pregnancy Calculator: How Pregnant Am I?

It’s positive! You’ve done the test and confirmed your pregnancy — now the question is when? How far along are you? What is your estimated due date (EDD)?

When Exactly is Week 1?

To answer this question, you have to first understand the 40-week pregnancy term. Technically, from conception to delivery, a full-term pregnancy is around 37 weeks. So how did the 40-week term come about?

A woman becomes pregnant when her egg is fertilised by a sperm. While it’s possible to determine the date of ovulation (though very few women do), we simply do not know the exact date of conception. What you do know, however, is the first day of your last menstrual period (LMP), which is usually 2 weeks before you ovulate. As such the start of the pregnancy is set as the first day of your LMP. In other words, for the first 2 weeks or so of your pregnancy, you’re not actually pregnant!

When Am I Due?

You can calculate your EDD by simply counting 40 weeks from the first day of your last menstrual period. That’s 280 days and assumes that you are on a 28-day cycle. Of course some babies decide to arrive early while others arrive late, so your EDD can only be an approximation of when you meet your new arrival — which in reality could be as much as one week before or after.

How Accurate is It?

You will still need to see your obstetrician if you want a more accurate EDD. Dr Tan Thiam Chye, an obstetrician and gynaecologist, highlights that ultrasound imaging enables doctors to see the pregnancy very clearly. “When we do a scan, we will see the pregnancy through different ages. This lets us date the pregnancy very accurately.”

There are consistent signs that point to certain stages of foetal development — a measurable heartbeat points to Week 6; the shape of a small baby will be visible around Week 7 or Week 8. You can find out more about what happens in Trimester 1 here.

By determining how far along you are, the doctor will be able to accurately estimate when your baby is due.

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A/Prof Tan Thiam Chye
MBBS (S'pore), M.Med(O&G) (S'pore) Head & Senior Consultant Department of Obstetrics and Gynaecology KK Women's and Children's Hospital Director (Clinical), Office of Patient Experience Deputy Director (Education), KKH Campus Associate Professor Duke - NUS Graduate Medical School Singapore

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