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Overview

The beginning of this week starts with the onset of your period.  Although you aren't even pregnant yet, your doctor will use the first day of your last menstrual period to provide a simple way to calculate how far along your pregnancy is.  Commonly referred to as "Day 1" by health care providers, your period starts when your uterus senses that you are not pregnant.  Usually, your period will last somewhere between 4 and 8 days, and between 1 and 2 ounces of blood is lost during this time.

Uterine cramping, backache, bloating, nausea, diarrhea, headache, breast tenderness, irritability, and fatigue are all common complaints during this week. 

What is happening in my body?

The uterus is a pear-shaped organ in your lower abdomen.  The inside of the uterus contains a thick, soft lining called the  endometrium.  The endometrium is well-supplied with blood vessels in preparation for a pregnancy. 

Estrogen and progesterone, hormones that are secreted by the ovaries, drop sharply during the days before your period starts.   This drop in estrogen and progesterone sends a message to the blood vessels in the endometrium to close off, which stops blood flow to the endometrium.  Blood to this area then pools and bursts, causing your period.  Menstrual flow consists of blood, endometrium, and mucus from the uterus and vagina.

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Next Week

Of Note This Week

Menstrual Cramps

What causes cramps?  What can you do about them?  When is the pain severe enough to warrant a call to the doctor?  

Menstruation

The dip in estrogen and progesterone also stimulates an area in the brain called the hypothalamus to secrete a hormone called GnRH (gonadotropin-releasing hormone).  GnRH makes a short trip to another area in the brain called the anterior pituitary gland.  The anterior pituitary gland then begins to secrete a key hormone called FSH (follicle-stimulating hormone). (The anterior pituitary gland also secretes LH, which we will discuss next week.)  FSH travels to your ovaries and stimulates between 3 and 30 follicles, causing them to begin to prepare for ovulation.  These follicles are already beginning to grow as you are having your period.