Find out how far along you were in pregnancy on
a particular date with our calculator. The calculator assumes 28 day
cycles with ovulation on day 14 of the cycle.
How far long was I on
The chart below shows the age when different organ systems
Central Nervous System
The red bars in the table show the gestational age when different organ systems are most sensitive to major birth defects in that organ system. The
pink bars show the gestational age when different organ systems are sensitive to functional defects and minor malformations.
Most substances that cause birth defects produce their
effect during the sensitive 5th to the 10th week (embryonic period) of
development when the major organs are forming during the first trimester . For example, thalidomide causes
limb defects when taken during the the 21st to the 36th day after conception. Tetracyclines do not produce their effects until after the first trimester
when the skeletal system begins to form bone. Some drugs such as
ethanol may produce harmful effects on functional development throughout
Conceptual age =The time elapsed since the day of conception Gestational age (or “menstrual age”)= The time elapsed since the
first day of the last normal menstrual period
1. Moore KL, Persaud TVN, The developing
human: clinically oriented embryology, 7th edition, Saunders, 2003:520.
2. Sandler TW. Langmans’s Medical Embryology, 7th ed.Baltimore: William and
Engle WA; American Academy of Pediatrics Committee on Fetus and Newborn.Age
terminology during the perinatal period. Pediatrics. 2004