Most women, however, can recall when they had their last period.

So doctors use the first day of your last menstrual period (LMP) to calculate your due date.

In contrast, embryologists and other reproductive biologists more often employ ovulatory age or fertilization age, both of which are typically 2 weeks of pregnancy shorter than the dating system used by obstetricians.

The ovarian cycle is divided into three stages: the follicular phase, ovulation, and the luteal phase.

Follicular Phase The follicular phase begins on the first day of your menstrual cycle, and it ends right before ovulation.

This is known as your LH surge (which is what ovulation predictor kits measure).

Ovulation Within 24 to 36 hours after the LH surge, ovulation takes place.

As the follicles mature, the level of estrogen increases.

Estrogen tells the hypothalamus to stop producing FSH.

The most common signs and symptoms of early pregnancy are: Every month, a mature egg is released from one of your ovaries.

(Occasionally, you may release more than one egg.) This is called ovulation, and it’s the key to becoming pregnant.

It helps if you consider your due date as a rough estimation of the range of time your baby might be born, rather than the day your baby will definitively make an appearance into the world.