Infertility In Women - Introduction

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LH serves two important roles:

• First, the LH surge around the 14th cycle day stimulates ovulation. It does this by causing the dominant follicle to burst and release its egg into one of the two fallopian tubes. Once in the fallopian tube, the egg is in place for fertilization.
• Next, LH causes the ruptured follicle to develop into the corpus luteum, a yellow mass of cells. The corpus luteum provides a source of estrogen and progesterone during pregnancy.

Click the icon to see an image of the corpus luteum.

Fertilization. The so-called "fertile window" is 6 days long and starts 5 days before ovulation and ends the day of ovulation. Fertilization occurs as follows:

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• The sperm can survive for up to 3 days once it enters the fallopian tube. The egg survives 12 - 24 hours unless it is fertilized by a sperm.
• If the egg is fertilized, about 2 - 4 days later it moves from the fallopian tube into the uterus where it is implanted in the uterine lining and begins its 9-month incubation.
• The placenta forms at the site of the implantation. The placenta is a thick blanket of blood vessels that nourishes the fertilized egg as it develops.

Click the icon to see an image of the placenta.

• The corpus luteum (the yellow tissue formed from the ruptured follicle) continues to produce estrogen and progesterone during pregnancy.

If the egg is not fertilized, the corpus luteum degenerates into a form called the corpus albicans, and estrogen and progesterone levels drop. Finally, the endometrial lining sloughs off and is shed during menstruation.

Review Date: 11/10/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org).