Sleep-MOMagement: Improving Postpartum Sleep in First-time Mothers Through Tailored Behavioral Approaches.

Inclusion Criteria: Women are eligible for study participation if they: * (1) Have had a singleton pregnancy. * (2) Are between 4 to 12 months postpartum with their first child. * (3) Exhibit (sub)clinical insomnia, operationalized as an Insomnia Severity Index (ISI) score greater than 7 7 and having answered 'yes' on the following three statements: a) I have trouble falling asleep, and/or staying asleep and/or I have early morning awakenings AND this causes daytime symptoms. b) My sleeping problem is not caused by an external factor (the baby or my partner). c) These sleeping problems occur at least 3 times a week for at least 3 months. * (4) Have access to a telephone, computer, and email. * (5) Possess adequate Dutch literacy to comprehend therapy content, questionnaires, and instructions. Exclusion Criteria: Women are excluded from participation if they: * (1) Are currently pregnant. * (2) Are shift workers. * (3) Have severe diagnosed psychopathologies (e.g., bipolar disorder, post-traumatic stress disorder, psychosis) * (4) Have current severe or untreated sleep disorders (narcolepsy, restless legs syndrome, circadian rhythm disorders) * (5) Have an unstable medical condition that may disrupt sleep. * (6) Have received cognitive-behavioural therapy for insomnia (CBTi) within the last 6 months. * (7) Experience sleep deprivation due to unsettled infant sleep/wake behaviour, defined as the infant waking more than three times per night for more than 30 minutes and requiring parental support to re-initiate sleep.