Pregnancy week 1
It is surprising to note that the start of a woman’s last period is actually the first week of her pregnancy. Since conception transpires about two weeks after the menstrual cycle commences, due dates are calculated by including the last week of the period in the 40 weeks of pregnancy. Common symptoms during the first week of pregnancy occur after about 10-14 days after ovulation and include cramps, a higher amount of vaginal discharge than usual, an increase in body temperature to about .6 degrees, fatigue, nausea, tenderness of breasts, frequent urges to urinate, a metallic taste in the mouth, and a missed period.
The early weeks of pregnancy bring about a vast amount of changes in the body. Hormone levels fluctuate in order to guarantee a thick lining of tissue to sustain the fertilized egg. Ovulation occurs around the 14th day of the 28 day menstrual cycle. One or more eggs are dropped by the follicles into the Fallopian tubes where they await fertilization by a single or more sperm. Gender is determined by whether the sperm is carrying a Y chromosome, which produces a male, or an X chromosome, which produces a female. As the fertilized egg multiplies, it develops into a ball of cells called a blastocyst and from that ball a recognizable baby form eventually emerges.
Alcohol, second-hand smoke, and drugs, even many over the counter medicines, are potentially harmful for the growing baby. It is important to discontinue these bad habits as soon as the potential for pregnancy is apparent. Smoking is known to cause an increase in the baby’s risk of being underweight and underdeveloped for the proper gestational age. It also prevents the absorption of folic acid into the baby’s body. Risks such as pulmonary diseases and placenta previa are also very real threats caused by pregnant smokers. Alcohol consumption during pregnancy can lead to speech problems in the baby’s life later on and motor development disabilities. Fetal irregularities can occur even when there has been very little alcohol consumption. Also, in order to prevent neural tube defects, soon-to-be mothers should begin taking at least 400 micrograms of folic acid as soon as they become aware of their pregnancy.
Current guidance (today's medical sources): By medical convention pregnancy is dated from the first day of the last menstrual period, so the last week of the period is counted within the 40 weeks even though conception happens about two weeks later. Ovulation usually occurs around day 14 of a 28-day cycle, when one or more eggs are released into the fallopian tubes to await fertilisation; the baby's sex is set by whether the sperm carries a Y or X chromosome. Early signs, when present, can include cramping, more vaginal discharge, a slight rise in body temperature, fatigue, nausea, tender breasts, frequent urination, and a missed period. It is commonly advised to avoid alcohol, second-hand smoke, and unverified medicines, and to take about 400 micrograms of folic acid a day to help reduce the risk of neural-tube defects.
Contact your healthcare provider promptly about heavy vaginal bleeding, severe or persistent abdominal pain, a high fever, severe or sudden headache, vision changes, or fainting. Seek urgent care if you are worried — these can be signs that need medical attention.
Sources: ACOG — Pregnancy (FAQ / month-by-month); CDC — Folic Acid; NHS — You and your baby at 1 to 3 weeks of pregnancy. Informational only. See our sources & medical-review policy.
Frequently asked questions
How many months is 1 weeks pregnant?
Week 1 falls in the first trimester. Pregnancy is usually counted in weeks (about 40 in total) rather than months, because weeks are more precise.
What is happening to the baby at 1 weeks?
In weeks 1–2 conception has not yet occurred; hormone levels build a thick uterine lining and the body prepares to ovulate.
What symptoms are common at week 1?
The last menstrual period marks week one; any early symptoms typically appear about 10–14 days after ovulation. Symptoms vary a lot from person to person; discuss anything that worries you with your healthcare provider.
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See every week from 1 to 40, grouped by trimester.
See the week-by-week guide →Informational only — not medical advice. Pregnancy Week to Week is a general educational reference. It is not a substitute for professional medical care, diagnosis, or treatment. Every pregnancy is different: always consult your doctor, midwife, or other qualified healthcare provider about your own pregnancy, and never disregard or delay professional advice because of something you read here. In an emergency, contact your maternity unit or local emergency number immediately.