Pregnancy Terms

Pregnancy: In humans, pregnancy is the state of carrying a developing embryo or fetus (baby) within the female body as the result of fertilization (also known as conception) which occurs when the female’s ovum (egg) and the male’s spermatozoon (sperm) unite. The fertilized egg (initially known as a zygote and which has the entire genetic make-up of the baby, including its sex) begins dividing rapidly into many cells. Now also known as a blastocyst, it normally implants in the lining (endometrium) of the females’ uterus (womb) within 24 hours. The condition of pregnancy lasts from conception to birth. The developing baby is called an embryo for the first eight weeks following fertilization and then is called a fetus until expelled from the uterus (born). The length of pregnancy (gestational period) averages 270 days from fertilization but normally is counted from the first day of menses prior to conception (approximately 284 days). Gestation is divided into three periods of time called trimesters.

Conception: Medically, as applied to humans, in recent years this term has been used differently by different groups to describe the onset of pregnancy. Webster’s www.medterms.com gives both definitions. Traditionally conception describes the union of the spermatozoon (sperm) and ovum (egg) and is synonymous with fertilization. In recent years the term has been used by some to describe the onset of pregnancy as marked by the implantation of the blastocyst (fertilized egg) into the endometrium (lining of the uterus).

For the purpose of this website, the traditional definition is applied.

Cervix: The bottom opening to the uterus which stretches during labor or abortion.

Embryo: Human life in the earliest weeks of development when all the organs are formed.

Fetus: A developing unborn baby with an observable human structure.

Full Term Pregnancy: The stage at about 40 weeks from the beginning of your last menstrual period, when the unborn baby is ready for birth.

Last Menstrual Period (LMP): The date when a woman started her last menstrual period before conception. This is the point in time from which the pregnancy and the age of the unborn baby are measured.

Trimester: An interval of approximately three months used to measure three successive stages of pregnancy; first trimester, second trimester, and third trimester.

Uterus: Female organ where the unborn baby develops during pregnancy.