Figuring out the due date of a baby during a pregnancy is not an exact science. Many factors come into play, including knowing the actual day of conception and how far along the woman's pregnancy is. Even then, determining the exact date is difficult as many pregnancies can last longer than anticipated while, in some cases, the baby can come sooner than expected. Determining the due date for a baby requires the mother-to-be to take certain information into account when calculating.
Knowing the date of conception goes a long way toward determining the due date for a child. A woman who goes through a full-term pregnancy can expect it to range from 37 to 40 weeks, according to WebMD. Even this number is not always accurate, as it is only an estimate using the date of conception as a starting point.
Most pregnancies last for roughly 294 days and, even though some births do come early or late, most women usually deliver within 14 days of their due date, notes WebMD. A premature birth describes a pregnancy that takes place three weeks before the baby is due. Alternatively, a post-term or prolonged pregnancy is one that extends past the expected due date. While every mother-to-be hopes for a relatively healthy and problem-free pregnancy, it is necessary to keep in mind that usually any failure to properly calculate a due date is not a cause for alarm and is more than likely due to a simple miscalculation on the mother's or doctor's part.
Determining a Due Date
To determine a due date, many doctors perform testing using devices, such as an ultrasound. A doctor can also measure the size of the uterus to determine how far along a pregnant woman is starting at around 12 weeks into the pregnancy. An outlier to this method is in the case of a woman set to deliver twins with the uterus tending to stretch and grow sooner than for single childbirth.
A doctor might also use an ultrasound to help predict your due date. Unlike other methods, an ultrasound gives the doctor an accurate picture of how far along the fetus is in development, which in turn lets the doctor know exactly when a parent should expect the birth of their child.
Determining Due Date By Menstrual Cycle
Using the menstrual cycle represents a final method to use to determine a baby's due date, and it doesn't even require a doctor. The pregnant woman simply adds seven days to the first day of her last menstrual cycle and then subtracts three months from that to gain the month in which they can expect their child to arrive. For example, if a woman's last menstrual cycle was the first of January in 2017, she would add seven days to that total to get January 8. She would then subtract three months from that to get the birth month later in the year, which in this case is October 8, 2017. If the last menstrual cycle takes place later in the year, then the due date would fall in the following year.