Conception Calculator Based on LMP

Are you a 'to be' mother, who wants to find out when exactly was your baby conceived? It can be confusing to give the exact conception date without knowing the Last Menstrual Period (LMP) date. Using conception calculator based on LMP, you will be able to find the conception date.

Conception Date Calculator

As soon as the pregnancy is confirmed, the gynecologist and obstetrician calculate the due date. In determining pregnancy due date, the obstetrician and gynecologist uses two methods, namely ultrasound and the last menstrual period date. Likewise, to calculate the conception date, there are two methods. They are:

• Conception Calculator based on Due Date
• Conception Calculator based on LMP

In this article, we are going to focus our attention on conception calculator based on LMP.

Conception Calculator Based on LMP

When did a woman actually conceive, is usually not known to her under normal circumstances. The conception date is known to her only if she has undergone in vitro fertilization, or any other specialized treatment for fertility. Due date calculator is used to predict the approximate due date.

According to the statistics, only 1 in 20 babies are born on their estimated due date, which means that for majority of the women, there are always marginal errors of a few weeks on either side of the estimated due date. While calculating the estimated due date, also known as estimated delivery date (EDD in short), most obstetrician and gynecologist use Naegele Rule ^*. In this rule, the first day of the woman's last menstrual period is used. To the first day of the LMP, one year is added, then three months are subtracted. Then, 7 days are added to the result, to get the estimated due date.

^{* - This rule is named after Franz Karl Naegele, a German obstetrician.}.

Let us understand this with the help of an example. Suppose the LMP was 10 June 2009.

Due Date Calculation

LMP = 10 June 2009 Add one year to LMP = 10 June 2010 Subtract 3 months = 10 April 2010 Now add 7 days = 17 April 2010

If a woman has regular 28 day menstrual cycle, she will ovulate 14 days before her next period is due. This means she can get pregnant, approximately for 5 days of a month, because a sperm can stay for 3 to 5 days in the reproductive tract of the woman. Therefore, in case of an intercourse just a couple of days before the ovulation, the woman can still conceive. If the menstrual cycle of the woman is longer, in that case the day of ovulation will be more than 14 days and therefore the conception date also will be further ahead. Now let's take an example to understand how the conception calculator based on LMP works. Considering the LMP to be 1st January 2009, the table below gives the results.

Cycle Days	Conception Date*
25 day Cycle	12 January 2009
26 day Cycle	13 January 2009
27 day Cycle	14 January 2009
28 day Cycle	15 January 2009
29 day Cycle	16 January 2009
30 day Cycle	17 January 2009
31 day Cycle	18 January 2009
32 day Cycle	19 January 2009
33 day Cycle	20 January 2009
34 day Cycle	21 January 2009
35 day Cycle	22 January 2009
36 day Cycle	23 January 2009
37 day Cycle	24 January 2009
38 day Cycle	25 January 2009

^{* - The values in the table are approximate values.}

Conception Calculator Boy or Girl
To use the conception calculator to find out, whether the baby is going to a boy or a girl is complicated. The exact history of the ovulation cycle and LMP date is required for the same. Among the many methods available to predict the gender of the child, the most widely used method is the Chinese lunar pregnancy calendar. For more information, you may want to read trying to conceive a girl.

The conception calculator based on LMP is more accurate than the conception calculator based on due date, as the due date itself is an approximation. Even considering that fact that the sperm can stay in the reproductive tract for 3 to 5 days, the approximation by this method is far better.