Trimester 1 · week 1 of 40

1 week pregnant

Pregnancy is counted from the first day of the last menstrual period. That's why, in this first week of the obstetric count, there is no embryo yet.

Translated from the original Brazilian Portuguese content with the help of artificial intelligence. Read the original in Portuguese

At this point in the pregnancy count, there is no embryo yet.

Quick read

In 1 minute

The pregnancy count starts before fertilization.
The body is beginning a new menstrual cycle.
If pregnancy is possible, it's already worth reviewing habits, medications and supplements with your healthcare team.

Development

What happens at this stage

There is no baby developing yet this week. Gestational age is calculated from the last menstrual period because, most of the time, it isn't possible to know the exact day of fertilization. This standard lets professionals and tests use the same reference point throughout prenatal care.

Body and routine

What may change in your body

What's happening now is the start of a new cycle. Menstrual bleeding, mild cramps and changes in energy can be part of this phase. If you're planning a pregnancy, this is a good time to look after your health even before conception.

Possible steps

Care for this week

If you're trying to conceive, talk about folic acid and any other supplements recommended for your situation.
Review any ongoing medications with a professional; don't stop treatments on your own.
Avoid alcohol, tobacco and other exposures that could be harmful in a possible pregnancy.

Prenatal care focus

There is no prenatal care for this pregnancy yet, but a preconception visit can be useful to review vaccines, past illnesses, medications and family history.

Twin pregnancy

If you're expecting twins

It's not yet possible to talk about a twin pregnancy: fertilization hasn't happened yet.

Support network

For those by your side

Whoever is by your side can take part from the planning stage, helping to organize appointments, habits and expectations without turning trying to conceive into a source of pressure.

Common questions

Questions for this week

Am I already pregnant in week 1?

In the obstetric count, week 1 begins on the first day of the last menstrual period. Fertilization usually happens later in the cycle.

Can I take a pregnancy test?

At this stage it's too early for a test related to this cycle. The right time depends on ovulation and on a missed period.

When to seek care

Vaginal bleeding during pregnancy should be reported to your care team; how heavy it is, pain and gestational age change how urgent it is.
Severe, worsening or persistent abdominal pain deserves evaluation.
Fever, fainting, significant shortness of breath, chest pain or feeling very unwell need medical care.

In an emergency, go to the urgent care service in your area. This content does not replace a professional assessment.

Next · week 2

The next chapter

Next week, the body gets closer to ovulation and prepares the conditions for a possible fertilization.

See week 2

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Sources and transparency

Nilu editorial content, written from the official sources above. Individual clinical review of each week is in progress — this text is for information and does not replace your prenatal care.