A mother at eight weeks who says she is "just tired"

The intrusive images are the pivotal feature. Ego-dystonic, unwanted thoughts of harming the baby are common in postnatal depression and obsessive-compulsive presentations, and are not in themselves predictive of acting on them. They must, however, be distinguished from psychotic phenomena and from active intent.

I would ask directly and record answers to:

• Thoughts of ending her life, self-harm, or of harming the baby; whether she has a plan, intent, means, or has taken any step.
• Whether the images feel like her own thoughts or are experienced as imposed, and whether she believes the baby is in danger from an external force - command hallucinations, delusional beliefs or confusion would suggest postpartum psychosis, which is a psychiatric emergency requiring same-day assessment and usually admission.
• Whether she is alone with the baby for long periods, and who can be with her tonight.

Disposal: the absence of intent and psychosis allows a planned urgent referral rather than immediate sectioning, but she should not be left unsupported. I would arrange same-week (ideally within 24–48 hours) perinatal mental health or psychiatric review, involve the husband with her consent, and give a written crisis plan including the emergency department and hotline numbers. If intent, psychosis, or inability to care for the baby emerged, immediate emergency assessment and safeguarding referral would follow.

I would take the request seriously but reframe it. Her sleep disruption is likely driven by depression and anxiety rather than being a primary insomnia, so a hypnotic would treat the symptom and leave the cause untreated, while adding falls, sedation and dependence risk in a mother who must wake for a baby. The better answer is to treat the depression and to arrange practical night support.

Confidentiality is important to her engagement, and I would explain its limits explicitly rather than making a vague promise. Her husband does not need to be told every detail, but he does need to understand that she is unwell and that the baby's safety depends on support at home. I would negotiate what she is willing to share, and explain that if I believed she or the baby were at immediate risk I would have to act, with or without her agreement.

I would also screen for bipolar disorder before starting an antidepressant, because a history of elevated mood, reduced sleep with high energy, or previous postpartum psychosis changes the treatment entirely - an antidepressant alone can precipitate mania. A thyroid function test and full blood count are reasonable given fatigue and the postnatal period, but they should not delay mental health referral.

Sertraline is a sensible first choice during breastfeeding: it has a relatively large body of lactation safety data, low milk transfer, and a favourable interaction profile. I would start at 50 mg daily and review at one to two weeks for tolerability and at four to six weeks for response, rather than expecting an immediate effect.

Before starting I would:

• Confirm there is no history of mania or psychosis.
• Explain the small but real risk of transient neonatal irritability and the importance of reporting it, while making clear that untreated maternal depression carries its own risks to the mother–infant relationship.
• Avoid sedating agents such as amitriptyline or mirtazapine as first line in a mother who must wake at night, unless sleep is the dominant problem and the risks are discussed.

Monitoring should cover suicidal ideation, especially in the first few weeks, the intrusive thoughts, bonding, and the baby's feeding and behaviour. I would also arrange psychological support, which is often as important as medication, and document the risk assessment and safety plan. If she developed psychotic symptoms or intent at any point, the plan changes to urgent psychiatric assessment rather than medication adjustment in primary care.