Expected date of delivery

Expected Date of Delivery (EDD), also known as due date or estimated date of confinement (EDC), is the estimated date when a pregnant woman is expected to give birth. The calculation of the EDD is an important aspect of prenatal care and is used to monitor the progress of the pregnancy, schedule prenatal tests, and plan for the birth. Understanding the methods used to estimate the due date and the factors that can influence the accuracy of these estimates is crucial for healthcare providers and expectant parents alike.

Calculation Methods

There are several methods used to calculate the EDD, with the Naegele's Rule and ultrasound measurements being the most common.

Naegele's Rule

Naegele's Rule calculates the due date by adding one year, subtracting three months, and adding seven days to the first day of the woman's last menstrual period (LMP). This method assumes a regular 28-day menstrual cycle and ovulation occurring approximately 14 days from the start of the cycle.

Ultrasound Measurement

Ultrasound measurement in the first trimester is another common method to estimate the due date. It involves measuring the size of the embryo or fetus to determine the gestational age. This method is considered more accurate than Naegele's Rule, especially when performed in the first trimester.

Factors Influencing the Accuracy of EDD

Several factors can influence the accuracy of the EDD, including the method used to calculate it, the regularity of the woman's menstrual cycle, and the timing of the ultrasound measurement.

Irregular Menstrual Cycles

Women with irregular menstrual cycles may have less accurate EDDs if the calculation is based solely on LMP.

Timing of Ultrasound

Ultrasounds performed in the first trimester are generally more accurate for dating the pregnancy than those performed later.

Importance of Accurate EDD

An accurate EDD is important for several reasons. It helps healthcare providers monitor the pregnancy's progress, plan for medical interventions if necessary, and prepare for the birth. It also allows expectant parents to plan for the arrival of their baby.

However, it is important to note that the EDD is an estimate, not a guaranteed delivery date. Only about 5% of babies are born on their exact due date, with most births occurring within a week before or after the EDD.