There are multiple ways to calculate the delivery date. To determine an expected delivery date, using a delivery date calculator, you need to know either the first day of your last period or the date of conception.
In cases when a child is conceived via IVF, then the transfer date is used to calculate the expected date of delivery. However, if none of these dates is known, doctors use an ultrasound scan to find the delivery date.
Let’s now learn about these factors in detail.
1. First Day of Your Last Period
Generally, pregnancy lasts for around 38-40 weeks. So, count 40 weeks or about 280 days from the first day of your last menstrual cycle to find when you are due. Another way is to subtract three months from the last menstrual period and add seven days.
This is the most used method of finding one’s due date. However, you must also keep in mind that this is just an expected date. There is a chance that the baby will come early or a few days after the due date.
2. Conception Date
Only a few women actually know their date of conception. It is only possible if they track their ovulation symptoms. If you are one of them, then you can put that date in the pregnancy due date calculator to know your expected delivery date.
You can also use the traditional way, adding 266 days from the conception date. This will also provide you with an expected date. Nevertheless, knowing the due date is beneficial in many ways. Primarily it helps new parents to prepare for the baby.
3. IVF Transfer Date
If you have conceived using IVF or In-Vitro Fertilisation, you can use your transfer date to find your date of delivery. In this process, mature eggs are retrieved along with fertilised sperms. Then the fertilised eggs or embryos are transferred to the uterus.
After Day 5 embryo transfer, you need to count 261 days from your transfer date. Whereas if you go with the Day 3 embryo transfer, you need to count 263 days. So, depending on the type of transfer, put the date on the due date calculator.
4. Ultrasound Scan
Suppose you do not remember the first date of your last period, the conception date or even did not understand the ovulation symptoms. One way to find how far you are along is to do your first prenatal ultrasound.
Here are the following clues that help a doctor calculate the delivery date.
Going through an early ultrasound can more accurately determine the delivery date. However, not every woman is prescribed an early ultrasound as it depends on the doctors they rely on.
While some suggest routine ultrasound, others only recommend it when periods are delayed, you are 35+, or you have a history of miscarriages. Sometimes, they prescribe this scan if they are unable to find the due date through a physical exam or last menstrual period.
Another clue that helps doctors determine the delivery date is by listening to a baby’s heartbeat. Generally, around the 9th or 10th week, doctors suggest a scan to monitor the foetus's heartbeat.
Sometimes later, when you start feeling the foetal movement, your doctor will suggest another scan around the 18th or 22nd week. This is to monitor the baby’s movement and also to speculate when your due date.
Another check performed by doctors is your fundal height. It is the measurement from your pubic bone to the uterus. This gap is checked every time you are visiting for a prenatal check-up. Monitoring this gap indicates how far you are from your due date.
Some doctors can tell an approximate delivery date by checking the size of your uterus during the initial prenatal exam. Although these factors indicate a more precise delivery date, you must be prepared beforehand.
