pregnancy

Introduction & Top Questions
The normal events of pregnancy
- Initiation of pregnancy
- Diagnosis of pregnancy
  - Symptoms and signs; biological tests
  - Conditions that may be mistaken for pregnancy
  - Duration of pregnancy
- Anatomic and physiologic changes of normal pregnancy
  - Changes in organs and tissues directly associated with childbearing
    - Ovaries
    - The uterus and the development of the placenta
    - Uterine tubes
    - Vagina
    - External genital structures
    - Other pelvic tissues
    - Breasts
  - Anatomic and physiologic changes in other organs and tissues
    - Cardiovascular and lymphatic systems
    - Respiratory tract
    - Gastrointestinal tract
    - Liver
    - Urinary tract
    - Blood
    - Endocrine system
    - Skin
  - Metabolic changes
    - The basal metabolic rate
    - Weight
    - Protein
    - Carbohydrates
    - Fat
    - Water
    - Minerals
- Prenatal care and testing
  - Ultrasound
  - Amniocentesis
  - Chorionic villi sampling
  - Alpha-fetoprotein screening
Abnormal changes in pregnancy
- Ectopic pregnancy
- Abortion
- Systemic diseases and pregnancy
  - Heart disease
  - Endocrine diseases
    - Diabetes
    - Thyroid disease
    - Pituitary disorders
    - Adrenal glands
  - Urinary tract diseases
  - Pulmonary disease
  - Gastrointestinal diseases
  - Nervous system disorders
- Diseases of pregnancy
  - Hypertensive disorders of pregnancy
  - Gestational diabetes
  - Diseases of the placenta
    - Placenta praevia
    - Abruptio placentae
    - Placental infarction
    - Placenta accreta
    - Placental cysts and benign tumors
    - Inflammation of the placenta
    - Placental anomalies
  - Anomalies of the umbilical cord
  - Abnormalities of the amniotic fluid
    - Hydramnios
    - Oligohydramnios
  - Trophoblastic disease
    - Hydatidiform mole
    - Choriocarcinoma

References & Edit History Related Topics

Images, Videos & Interactives

Close-up of a home pregnancy test device showing a blue plus sign in the result window, indicating a positive result for pregnancy.

Diagram showing the female reproductive system with labeled ovaries, fallopian tubes, uterus, and vagina, alongside hormone pathways and the process from ovulation to fertilization and early embryo development.

How does a home pregnancy test work?

Learn how researchers use biobanks, such as the Improved Pregnancy Outcomes by Early Detection study, or IMPROvED to improve maternal and newborn outcomes

A pregnant woman lies on an exam table smiling while a healthcare professional performs an ultrasound, with the baby's image visible on the monitor.

Cross-sectional medical illustration of a human uterus at seven weeks of pregnancy, showing the developing embryo inside the amniotic sac, placenta, umbilical cord, uterine wall layers, cervix, and vagina, with labeled anatomical structures related to gestation and embryology.

Three labeled cross-section diagrams show the development of a human embryo implanted in the uterine lining at 7.5, 13, and 23 days, highlighting structures such as the embryonic disk, amniotic cavity, yolk sac, trophoblast, and chorion.

At a Glance

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pregnancy summary

Related Questions

Close-up of a home pregnancy test device showing a blue plus sign in the result window, indicating a positive result for pregnancy. — Home pregnancy tests Devices for individual use at home detect pregnancy by measuring levels of the hormone human chorionic gonadotropin (hCG) in urine.

pregnancy

medicine

Written by

John W. Huffman

Fact-checked by

Britannica Editors

Last updated

Nov. 8, 2026 •History

pregnancy, process and series of changes that take place in a woman’s organs and tissues as a result of a developing fetus. The entire process from fertilization to birth takes an average of 266–270 days, or about nine months. (For pregnancies other than those in humans, see gestation.) A new individual is created when the elements of a potent sperm merge with those of a fertile ovum, or egg. Before this union both the spermatozoon...

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