Can a one week pregnancy be detected

Learn about week one pregnancy symptoms, how to identify the early signs, and find out why your due date is calculated from this point on.

Updated on September 21, 2022

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Learn about week one pregnancy symptoms, how to identify the early signs, and find out why your due date is calculated from this point on.
How Big Is Baby?
Your Changing Body
Week 1 Baby Development
Week 1 Tip
Week 1 Ultrasound
Watch Baby's Growth
Pregnancy Week 1 To-Do List
Pregnancy Week 1 FAQs
Must Reads
Signs of Pregnancy/The Pregnancy Test
What are the signs of pregnancy?
What is a pregnancy test?

How Big Is Baby?

While it seems like you'd be able to detect pregnancy from week 1, that's not how pregnancy tests work. That's because your due date is calculated from the first day of your last menstrual period. Conception occurs about two weeks from this day, and that's when you're truly considered pregnant. In just 40 short weeks, your baby will grow from the size of a tiny seed to the size of a plump watermelon.

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Your Changing Body

Starting as early as week 1 (while you're trying to conceive), start making healthy changes to ensure that your body is in the best shape for carrying and nurturing your baby. The biggies: cut out alcohol, cigarettes, and any illegal or recreational drugs. You may also need to switch or stop taking some prescription and over-the-counter medications. So tell your doctor that you're trying to conceive and make sure any medications you're using are safe.

SEBASTIAN KAULITZKI/SCIENCE PHOTO LIBRARY

Week 1 Baby Development

Baby? What baby? This concept may be a little hard to wrap your head around, but even though you're technically in the first week of pregnancy, you're not quite expecting—yet. Here's the deal: Because it's generally impossible to know the exact moment of conception, most healthcare providers count 40 weeks from the first day of your last menstrual period (LMP) to calculate your due date. According to this method, they date the beginning of "pregnancy" from about two weeks before the sperm penetrates the egg — which is where you are right now. Already spotted that pink line on a home pregnancy test? You're further along than you think, so skip ahead to Week 4.

Week 1 Tip

During week 1 of pregnancy or earlier is a good time to speak with your doctor about adding a prenatal multivitamin to your morning routine. At least 400 micrograms of folic acid every day can help prevent certain birth defects that affect your baby's brain, heart, and spinal cord, especially if you take it before you conceive and in the early weeks of your pregnancy. See that your supplements contain added goodies like calcium, iron, and Vitamin B12 as well.

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Week 1 Ultrasound

There's no ultrasound image of your baby-to-be for weeks 1 and 2. While your health care provider counts these two weeks toward your due date, you aren't really pregnant. Confused? Your pregnancy due date is calculated using the first day of your last menstrual period (LMP). Obviously you weren't pregnant at that time, but it's the best reference your health care provider has for estimating baby's arrival day (until you get an ultrasound, which may provide a more accurate due date).

Pregnancy Week 1 To-Do List

Start taking a prenatal vitamin if you haven't already.
Write down the date of your last period or two.
With your partner, create a family health history, including any genetic or chromosomal disorders.
Quit smoking, and cut out any other bad health habits.

Pregnancy Week 1 FAQs

How early can I take a home pregnancy test?

Must Reads

Signs of Pregnancy/The Pregnancy Test

What are the signs of pregnancy?

The signs of pregnancy vary from woman to woman. Usually the most obvious sign is the absence of menstruation (amenorrhea). However, some women continue to have bleeding even while pregnant. The following are the most common first signs of pregnancy. However, each woman may experience the signs of pregnancy differently. These may include:

Extreme tiredness
Sore and swollen breasts
Nausea or vomiting (also called morning sickness)
Frequent urination
Certain food cravings or aversions
Bloating of the belly
Darkening of the skin around the nipples (also called the areola).

These early signs may not positively indicate pregnancy, but may actually signal another process happening within the body. A pregnancy test can provide more accurate results.

What is a pregnancy test?

Pregnancy is confirmed with a pregnancy test. A pregnancy test can be done on either urine or blood. Pregnancy tests find the presence of human chorionic gonadotropin hormone (hCG). This is a hormone made by the placenta about 10 days after fertilization. Levels of the hCG hormone approximately double every two days during the first 60 days of pregnancy. Pregnancy tests that use the woman's blood are done by a healthcare provider usually to get a very early diagnosis of pregnancy or to confirm an at-home pregnancy test. Blood tests are very accurate and can find pregnancy by the second week after conception.

Women can conduct an at-home pregnancy test by testing a sample of urine about two weeks after conception, or about the time a period is due. Home pregnancy tests have become more accurate in the last decade. If the test is used correctly, most home pregnancy tests are 97% to 99% accurate.

Always talk with your healthcare provider to confirm a positive at-home pregnancy test with a more reliable pregnancy test and physical exam. If your at-home pregnancy test results are negative, and you think you are pregnant, you should also talk with your healthcare provider.