Reproductive system: female cycle, pregnancy, lactation, contraception basics
Physiology · MBBS
Fetal development
Interactive 3DTravel week by week from fertilized egg to fetus.
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Study notes
A woman's periods stop; urine pregnancy test is positive at 6 weeks. After fertilization, the implanting embryo secretes hCG — rescuing the corpus luteum so progesterone keeps the endometrium (no shedding = no period). hCG doubles every ~2 days, detectable in urine by 4–6 weeks. By week 10 the placenta makes its own progesterone/estrogen. The missed period is thus the first sign — the physiology explains both the symptom and the test.
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