When does the third trimester technically start?

The third trimester typically begins at 28 weeks gestation, though some definitions use 27 weeks. Week 28 is the standard clinical threshold.

Is it normal to still feel morning sickness in the second trimester?

For most, morning sickness resolves by weeks 12–14. About 10–15% of women experience nausea into the second trimester. Hyperemesis gravidarum (severe pregnancy nausea) may persist throughout.

Pregnancy Trimesters: What Changes Each Week in Your Body and Your Baby

First Trimester: Weeks 1–12

Weeks 1–4: Implantation, hCG production begins, missed period. Weeks 5–8: Embryo forms major organs; heart begins beating (week 6); morning sickness peaks (weeks 6–9). Weeks 9–12: Embryo becomes a fetus; all major organs present though not fully developed; nuchal translucency screening at week 11–12.

Second Trimester: Weeks 13–27

Weeks 13–16: Fetus grows rapidly; gender visible by week 14–16. Weeks 17–20: Quickening (first felt movements) typically at week 18–20; anatomy scan at week 18–22. Weeks 21–27: Lung development; eyelids open; viability threshold at 22–24 weeks. Nausea typically resolves; energy returns.

Third Trimester: Weeks 28–40

Weeks 28–31: Brain development accelerates; baby can hear; Braxton Hicks contractions begin. Weeks 32–36: Baby gains weight rapidly (200g/week); head-down presentation by week 32–34 typically. Weeks 37–40: Lungs mature; baby considered full-term at 37 weeks. GBS testing at 35–37 weeks.

Using the Pregnancy Calculator

Enter your LMP date in Pregnancy Calculator to see your current gestational week, trimester, estimated due date, and key milestone dates. The calculator adjusts for cycle length if yours differs from the standard 28 days.

Pregnancy Trimesters: What Changes Each Week in Your Body and Your Baby

First Trimester: Weeks 1–12

Second Trimester: Weeks 13–27

Third Trimester: Weeks 28–40

Using the Pregnancy Calculator

Frequently Asked Questions

Track your pregnancy week

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