A Reproductive Lexicon


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A trimester is a three-month stage of pregnancy. Classically, pregnancy is nine months (40 gestational weeks) and is divided into three trimesters: the first trimester is the first three months (1-12 gestational weeks), the second trimester is the middle three months (12-28 gestational weeks), and the third trimester is the last three months (28-40 gestational weeks).