mybabybase

First trimester

1 week pregnant

There's no baby to measure yet this week.

Week 1 of 40 · in your first trimester · Updated

Your baby this week

By doctors' counting, week 1 starts at your last period. Conception hasn't happened yet.

  • Pregnancy is counted from the first day of your last menstrual period (LMP), not from conception. This is the convention every OB uses.
  • There's no embryo yet at week 1 — your body is finishing the previous cycle.
  • Conception typically happens at the end of week 2 or beginning of week 3.

Your body this week

Your body is preparing to ovulate. A great time to start prenatal vitamins if you haven't.

  • Your period is happening. Estrogen and progesterone are at their cycle lows.
  • Follicle-stimulating hormone (FSH) is rising and several follicles in the ovaries begin maturing — one of them will release an egg.
  • If you're tracking ovulation, this is the start of your fertile-window prep.

Common symptoms

  • Cramping
  • Period flow
  • Mood shifts

Things to do this week

  • Start a prenatal with 400 mcg folic acid
  • Cut alcohol; limit caffeine
  • Review medications with your provider

Tip

Start taking folic acid daily — it helps prevent neural tube defects.

For partners this week

Getting ready together

  • If you're trying for a baby, cut back on alcohol together so it isn't a solo effort.
  • Help make the daily folic acid a habit — keep the bottle somewhere you'll both see it.

Typical visits around this week

Based on a typical schedule in Ontario. Your doctor or midwife sets the actual timing.

Coming up

  • First prenatal visit

    Weeks 6–12

    Book with your doctor or midwife as soon as you know you're pregnant. This is usually the longest visit: your health and family history, medications, blood pressure and weight, and routine blood and urine tests (including your blood type and Rh factor). Your provider will also talk about your due date and the screening options ahead.

    Questions to ask →
    • When is my estimated due date, and how was it worked out?
    • Are my current medications and supplements okay to keep taking?
    • Who will care for me during pregnancy and birth, and where would I give birth?
    • Who do I call with questions or worries between visits?
    • Which vaccines should I plan for this pregnancy?

  • Dating ultrasound

    Weeks 7–12

    An early ultrasound that measures the baby to confirm how far along you are. Dating is most accurate between about 7 and 12 weeks, and the scan also confirms the pregnancy is in the uterus.

    Questions to ask →
    • Does this scan change my due date?
    • Can my partner come into the room?
    • Do I need a full bladder, and how should I prepare?
    • When will my provider get the results?

When to call your doctor or midwife

Bleeding, fluid leaking, a bad headache or vision changes, or baby moving less than usual all need a call. See the warning signs and who to call →

Next →Week 2

Follow your pregnancy week by week in MyBabyBase.

A due-date countdown, a mood and symptom journal, appointments, and a safe place for your documents — all in one hub.

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Further reading from health authorities