The first week of pregnancy can be confusing because pregnancy is usually dated from the first day of a woman’s last menstrual period. This means that during the first week of the medical pregnancy timeline, she is generally having her period and has not yet conceived.
Understanding this timeline helps explain what happens next.
1. The menstrual period begins: The uterus sheds its lining, producing menstrual bleeding. This is counted as the beginning of the pregnancy dating system.
2. Hormones begin a new cycle: Hormones from the brain and ovaries help prepare an egg for possible release later in the cycle.
3. An egg begins developing: Several follicles may start developing in the ovaries, although usually one becomes dominant and releases an egg.
4. The uterine lining begins to rebuild: After menstruation, the lining of the uterus gradually thickens in preparation for a possible pregnancy.
5. Ovulation is still ahead: In a typical 28-day cycle, ovulation may happen around day 14, but this varies considerably.
6. Fertilisation has not usually occurred yet: Because pregnancy dating starts before conception, there is generally no embryo during the first week counted by this system.
7. Pregnancy symptoms are not expected yet: Symptoms such as nausea and breast tenderness usually occur later, after hormonal changes associated with pregnancy.
When can pregnancy be detected? A pregnancy test detects human chorionic gonadotrophin (hCG), a hormone produced after implantation. Testing too early may give a negative result even when pregnancy later becomes detectable.
Final thoughts: The first week of pregnancy is mostly a dating convention rather than a week when an embryo is already developing. If you are trying to conceive, understanding your cycle and seeking pre-pregnancy health advice can help you prepare.
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