Even though it makes little logical sense, pregnancy is typically dated from the LMP (LMP = last menstrual period) instead...
Even though it makes little logical sense, pregnancy is typically dated from the LMP (LMP = last menstrual period) instead of conception. In reality, this means you get to count the two weeks before conception as part of the 40 weeks/280 days of pregnancy. The "typical" cycle is said to be 28 days (usually you have 28 days from the beginning of one period to the beginning of the next) and in that case, ovulation/conception would be on day 14. However, many women have longer or shorter cycles -- from perhaps 24 to 34 days. But what is important to note is that actual ovulation typically occurs 14 days before the next period is due, not simply at mid-point (or 14 days) in the cycle. So if Veronica is 40 days past her LMP and has a 28 day cycle, her due date calculated in the typical way would be correct without any adjustments. If, however, she had a 33 day cycle, her due date should be adjusted by 5 days -- which is what really counts to most women -- because she conceived five days after someone with a 28-day cycle, even if they have the same LMP. In math-speak: LMP date + cycle length - 28 = "Adjusted" LMP date Another example: If your LMP is October 22, with a cycle of say, 32 days, your adjusted LMP will be October 26. Why? Because (32 - 28 = 4 days) and then... 22 + that same 4 = 26 October. And one more variation: If your LMP is October 22, and you have a cycle length of 24 days, then the adjusted LMP will be October 18. (24 - 28 = minus 4 days) Clear as mud? Well, you can skip the equations and use our helpful little due date calculator tool instead.

recommended for you

Comments