“Denial of pregnancy is an important condition that is more common than expected, with an incidence at 20 weeks gestation of approximately 1 in 475. The proportion of cases persisting until delivery is about 1 in 2500, a rate similar to that of eclampsia. Denial of pregnancy poses adverse consequences including psychological distress, unassisted delivery and neonaticide. It is difficult to predict which women will develop denial of pregnancy. There are a number of forms of denial of pregnancy, including psychotic and non-psychotic variants. Denial of pregnancy is a ‘red flag’ that should trigger referral for psychiatric assessment.”
”However, there is often a poor outcome, with postpartum emotional disturbance and increased risk of fetal abuse, child neglect or neonaticide.1,4 There is also an increased incidence of precipitous or unassisted delivery (one study of 74 neonatal deaths revealed 18 cases that involved giving birth into toilets.1 The majority of these involved denial of pregnancy). Poor outcome is also due to preterm births, small for gestational age babies, increased rates of neonatal admissions and increased infant mortality.2,11,16
In July 2010, some French cases of neonaticide drew media attention;17 denial of pregnancy was thought to have played a significant role in some of these tragic situations. In instances of neonaticide, non-psychotic denial of pregnancy is most likely to result in passive death; the woman may become acutely confused and disorientated at the time of delivery, or panic after the birth and the infant may die from maternal negligence, through exposure. Psychotic denial is more likely to be associated with active killing, by means such as suffocation or strangulation.”
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3128877/
I am not insisting she was delusional, it is in her medical notes and the judge even commented on it:
Whilst the Jury did not accept that the balance of your mind was disturbed so as to justify a verdict of infanticide, in my judgment you had suffered from a degree of pregnancy denial, a condition that is, at least, recognised in the medical literature.