1 Week Pregnant

Baby’s Development

This first week of pregnancy is actually your menstrual period. Because your estimated due date (EDD) is calculated from the first day of your last menstrual period (LMP), this week counts as part of your 40-week pregnancy even though conception hasn’t occurred yet [1]. Your body is shedding the uterine lining from the previous cycle and preparing a new one. Hormones like follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are already at work recruiting follicles in your ovaries for the upcoming cycle [2].

Pregnancy Symptoms

You won’t experience pregnancy symptoms this week since conception hasn’t happened. What you’ll feel are typical menstrual symptoms: cramping, bloating, breast tenderness, mood changes, and fatigue. If you’re tracking your cycle, you may notice cervical mucus changes as you approach ovulation in the coming days. Some people also experience mittelschmerz (ovulation pain) around week 2 [1].

Body Changes

Your uterus is menstruating — shedding its lining. The pituitary gland releases FSH to stimulate follicle growth in your ovaries. One dominant follicle will emerge and release an egg around day 14 of a typical 28-day cycle (week 3 of pregnancy dating). Your basal body temperature is in its lower follicular phase [2].

Tips for Week 1

• Start a prenatal vitamin with folate (400-800 mcg) now if you haven’t already. Neural tube formation begins before most people know they’re pregnant [1].
• Track your cycle using an app, basal body temperature, or ovulation predictor kits to identify your fertile window.
• Schedule a preconception checkup if you haven’t had one recently — discuss medications, vaccinations, and any chronic conditions with your provider.
• Cut alcohol and limit caffeine to under 200 mg/day. Both can affect early fetal development [3].

Things To Do (Checklist)

• Start prenatal vitamin with folate (400-800 mcg)
• Track menstrual cycle and fertile window
• Schedule preconception appointment if needed
• Review medications with provider for pregnancy safety
• Reduce alcohol to zero; limit caffeine < 200 mg/day

Frequently Asked Questions

Q: Am I actually pregnant at week 1? A: Not yet. Pregnancy dating starts from the first day of your last period, so “week 1” is your period. Conception typically happens around week 2-3.

Q: Can I take a pregnancy test now? A: No. Tests detect hCG, which only rises after implantation (around week 4). Testing now will give a false negative.

Q: Should I stop exercising? A: No. Moderate exercise is encouraged while trying to conceive and throughout pregnancy unless your provider advises otherwise [1].

For Dads

• Start taking a men’s prenatal or multivitamin with zinc, selenium, and CoQ10 — sperm quality matters and takes ~74 days to improve [3].
• Cut back on alcohol — heavy drinking affects sperm count and motility. Aim for < 2 drinks/day [3].
• Join your partner for the preconception visit if possible — your medical history matters too.
• Talk about your timeline — when to stop contraception, how long you’re willing to try, next steps if it takes longer than expected.

Sources

1. ACOG — How Your Fetus Grows During Pregnancy
2. Mayo Clinic — Pregnancy Week by Week: First Trimester
3. Expecting Better — Emily Oster (Chapter 2: Conception)