Calculate your EDD — when is your baby due?
These ten months of pregnancy is a wonderful time for you to enjoy. However, it is crucial that you remain healthy, both physically and emotionally, to enjoy your pregnancy. Antenatal care is part of this preparation and your first visit to your
obstetrician (after your pregnancy has been confirmed) is an important occasion.
Your obstetrician would love to meet you and your partner together. Come prepared as he/she is likely to enquire about your previous medical history, previous pregnancies and outcomes or family history of genetic syndromes or diabetes. These significant information could impact the outcome of your pregnancy and thus, such pertinent details should not be missed.
drink alcohol, take any or use recreational drugs, you should inform your obstetrician as these may have an effect on your pregnancy. Rest assured that this information will be kept confidential.
The past obstetric history is crucial in every pregnancy. This includes details of previous
miscarriages or abortions (if any),
ectopic (outside the womb) pregnancies, any problems with fertility, and any problems during your previous pregnancies or childbirth. If you are unable to recall, try to get hold of the medical summaries of your previous pregnancies.
The first thing many mothers-to-be want to know when they first realize that they are pregnant is WHEN. When is the baby coming? They would love to know if they are expecting a Christmas baby or one that arrives on an auspicious birth date. Do keep track of the dates of the first day of your menstrual periods when you are trying to conceive. Many women forget this pertinent detail. The expected date of delivery (EDD) can be calculated from the first day of the last menstrual period (LMP) if you have a regular 28-day menstrual cycle.
Your baby was conceived about 14 days after the first day of your LMP. EDD is at 40 weeks — that is 40 weeks after the first day of your last menstrual period or 280 days after LMP or 38 weeks (or 266 days) since conception. It all corresponds to the same EDD. Amazing, isn’t it?
However, your pregnancy is only full-term at 37 weeks after LMP, i.e. your baby is fully matured and ready for delivery at any time. So get your maternity bag and baby cot ready by then!
Preterm (premature) delivery refers to a delivery before 37 completed weeks after LMP.
Calculate the expected date of delivery (EDD) using Naegle’s rule:
280 days from the first day of the last menstrual period (LMP), i.e. EDD = LMP (first day) + 7 days, and then going forward 9 months
For example: If the LMP is 11/5/2007, EDD = 11 + 7 (day), May + 9 months, i.e. 18/2/2008
(This rule is based on a menstrual cycle of 28 days and assumes ovulation occurred at mid-cycle. Where the cycle is regularly greater than or less than 28 days the calculation has to be adjusted accordingly, e.g. add a further 7 days for a 35 day cycle and subtract a further 7 days for a 21 day cycle.)
Most obstetricians are familiar with the pregnancy calender wheel (Figure 8.1). It helps estimate the EDD based on the LMP or dating scan. Do not be too worried if you have irregular periods or cannot recall your LMP. The most accurate dating is from first trimester ultrasound measurement of your baby’s size. Thus, see your obstetrician early in the
first 12 weeks of your pregnancy in order to get an accurate due date.
There are several pregnancy date calculators that are freely available from the Internet. Do a search engine for “pregnancy date calculator” and you will find them.
Do not be alarmed if you feel absent-minded and forgetful in pregnancy. You may find yourself misplacing your purse, forgetting to return phone calls, or going off to fetch something only to discover you have forgotten what you are looking for. This is reported by many mothers-to-be.
The exact cause is unknown. Hormonal changes, stress as well as preoccupation with thoughts of the pregnancy can contribute to this absent-mindedness.
Sleep could also be erratic during your pregnancy. You may become even more forgetful if you are tired during the day.
Source: Dr TAN Thiam Chye, Dr TAN Kim Teng, Dr TAN Heng Hao, Dr TEE Chee Seng John, The New Art and Science of Pregnancy and Childbirth, World Scientific 2008.
Visit Parent Hub, for more useful tips and guides for a healthy pregnancy.
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This article was last reviewed on
22 Nov 2023
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