Estimated date of delivery
The estimated date of delivery (EDD) for your baby is found by counting 40 weeks from the first day of your last monthly period.
What date will your baby be born?
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You'll want to know the estimated date. There are usually about 266 days or 38 weeks between conception and birth. This is the same as 40 weeks from the start of your last menstrual period (LMP) because ovulation, and therefore conception, is normally two weeks after the start of your period.
You can work out the approximate date of your baby's arrival by calculating from the first day of your last period. The estimated date of your baby's delivery (EDD) is therefore at 280 days (40 weeks) from the first day of your last period. How accurate this date is depends on whether you have a regular 28-day cycle. If your menstrual cycle is shorter or longer, your delivery date may be earlier or later.
Medical staff use the EDD when monitoring your baby's development and checking the expected rate of growth. Sometimes too much emphasis is put on this date, leading to unnecessary intervention, and doctors may want to induce labour if they believe your baby is overdue.
However, risks to you and your baby don't rise much until after 42 weeks, and most doctors are prepared to let a pregnancy continue, without inducing, if tests show the baby is not at risk (see Are you Overdue?).
How the EDD chart works
Find the first day of your last period on the chart by looking for the month in bold type on the left-hand side, and look along the line until you find the actual date of your LMP. Then look at the figure below it. This is your baby's estimated date of delivery (EDD).
Your baby's arrival and delivery date
Don't be anxious if your baby doesn't show signs of arriving on the day you'd expected. About 85 per cent of babies born from normal pregnancies are delivered within a week before or after the date predicted.
The EDD is used to give you an approximate idea of when to expect your baby to be born. It's best to be flexible and not to see this as the exact day you'll go into labour and deliver your baby. A healthy pregnancy may last for anything from 37 to 42 weeks.
Posted 16.11.2010
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