Mood swings during pregnancy

By trimester

Weeks 1–13

1st trimester

Mood swings often begin within a few weeks of conception, as estrogen and progesterone rise quickly. This early hormone surge affects the same brain circuits involved in irritability and stress response, so feeling more reactive than usual is a normal adjustment, not a sign anything is wrong.

Weeks 14–27

2nd trimester

Hormone levels stay high through the second trimester, and how strongly they affect mood varies a lot by person. Research suggests some people have a more hormone-sensitive nervous system, where irritability and anger show up earlier and more sharply than in others.

Weeks 28–birth

3rd trimester

Placental CRH pushes cortisol to roughly four times non-pregnant levels by late pregnancy, a normal, temporary shift tied to fetal brain development. Combined with poor sleep and physical discomfort, this can make the third trimester feel emotionally intense. Persistent sadness or hopelessness is a different pattern worth flagging to your provider.

What does the evidence show for mood swings?

• Hormonal shifts in pregnancy are a well-documented driver of sharp mood swings, which can begin within just a few weeks of conception. 1
• Rising estrogen acts on several brain neurotransmitter systems that influence mood and cognition, while the placenta raises cortisol to roughly four times non-pregnant levels by the third trimester as a normal, non-pathological adaptation tied to fetal brain development. 2
• Not everyone reacts to pregnancy hormone shifts the same way. Some people have a heightened neurobiological hormone sensitivity, and irritability or anger tend to be among the earliest, most sensitive markers of it. 3
• Perinatal depression is defined by at least five symptoms lasting a minimum of two weeks, which is the key line that separates it from ordinary hormonal mood swings. 4
• Routine depression screening during and after pregnancy is recommended because getting connected to care matters: perinatal depression that goes unaddressed carries serious risk, including suicide. 4

When should I call my provider about mood swings?

Sadness, hopelessness, or a loss of interest in things you normally enjoy that lasts most of the day for two weeks or longer is a different pattern from ordinary hormonal mood swings and meets the threshold clinicians use to identify perinatal depression. Any thought of harming yourself or feeling like your baby would be better off without you calls for reaching out the same day, whether that's your obstetric provider, a mental health professional, or a crisis line. Routine screening during pregnancy exists precisely because these symptoms are common and very responsive to support once they're identified. If you are ever unsure which side of the line you are on, make the call. Obstetric teams handle these check-ins as routine, not as overreacting.