Day 1
Week 1
What is happening to you physically

This is the first day of your last menstrual period (LMP), and according to the 40-week pregnancy timetable, it's the first day of your pregnancy. Doctors and midwives use the 40-week calendar because your LMP is an easy and reliable standard from which to calculate a due date. The length of your cycle, travel, stress and hormonal changes can all affect when you ovulate and when you conceive. Conception could happen as soon as a week from now, or three weeks from now or later, depending on your individual cycle.

The 40-week calendar is a way care providers can take these individual variations into account, while at the same time making sure the baby isn't threatening to arrive dangerously early or late. The age of a pregnancy determined this way is called gestational, or menstrual, age. If you know that your cycle is shorter or longer than 28 days (and most women's are), be sure to inform your care provider so a more accurate due date can be established. Right now, 3 to 20 eggs are beginning to mature in your ovaries. The one that's ready first will be released at ovulation. This phase of your menstrual cycle is called the follicular phase, for the sacs, called follicles, that the eggs reside in inside your ovaries as they grow.

Day 2
Week 1
What is happening to you physically

As you may remember from middle school health class, menstruation is when your uterus sheds its lining, known as the endometrium. The endometrium has only one function: to nourish the fertilized egg and support the placenta if you become pregnant. If you don't become pregnant, hormones signal the uterus to cut off blood supply to the uterine lining, killing the cells and causing the uterus to contract and shed the endometrial wall as it disintegrates. During this process, the unfertilized egg is shed or is reabsorbed by the body. The average blood loss during menstruation is about 4 1/2 ounces. If you become pregnant this cycle, this could be the last period you experience for about a year. And when your periods resume, if your baby was delievered vaginally, you'll find your cramps are much milder or even nonexistent.  Your levels of follicle-stimulating hormone (FSH) are peaking. FSH is the hormone that stimulates a select number of immature eggs to grow, mature and prepare to be released. Your FSH levels will peak again right before ovulation.