The mainstay of pharmacological treatment for non-psychotic mental disorders in the perinatal period is antidepressants. Data suggests that in Europe around 3% of pregnant women take an antidepressant at some point in their pregnancy, mostly selective serotonin reuptake inhibitors (SSRIs), with rates of around 10% reported in the USA.95 Antidepressants are effective treatments for depression, particularly for severe cases, and meta-analyses have shown that efficacy compared with placebo increases with severity of depression.96 Antidepressants are also effective for PTSD, anxiety disorders, and bulimia nervosa.97,98,99 However, partly because of the difficulties in undertaking RCTs in perinatal women, no trials have been done for perinatal disorders except for postnatal depression. These trials provide evidence of significantly higher response and remission rates for women taking SSRIs than for placebo. A Cochrane systematic review100 pooled data from three studies comparing SSRIs with placebo and reported significantly higher response (RR 1·43 [95% CI 1·03–2·03]) and remission rate (RR 1·79 [1·08–2·98]) for participants taking SSRIs than in those in the placebo group. However, the evidence-base is restricted because the three studies were very small, underpowered, and generally focus on women with mild-to-moderate postnatal depression.100 RCTs have so far not reported evidence of additional improvement with addition of a psychological intervention to antidepressants,101,102 nor for addition of sertraline by comparison with placebo for women given a psychotherapeutic intervention for postnatal depression, although the trials were underpowered.100 An RCT103 (n=61) reported significant improvements in EPDS scores in women given 17β-oestradiol skin patches (with dydrogesterone tablets for 12 days per month) compared with women given placebo, but adverse events were reported and there is therefore insufficient evidence to support use of oestrogens for postnatal depression.
Women often stop antidepressants during pregnancy104 and there is conflicting evidence on whether discontinuation is associated with an increased risk of relapse of depression,105,106 probably because of the different levels of severity of depression in the different study populations. However, recurrence after discontinuation consistently seems to be more likely in women with a history of several episodes or a recent episode.105
As a general principle, drugs in pregnancy should be minimised, and many women with perinatal mental disorders can be treated with non-pharmacological interventions. However, drugs will be clinically indicated for women with more severe mental disorders in which there are substantial risks to the mother, the pregnancy, and the fetus or infant.50,107 Clinicians and women therefore need to assess the benefits and risks of pharmacological interventions in pregnancy using key principles of prescription in the perinatal period (figure 2).108 Unlike other times in a woman’s life, risks of illness versus risks of drugs do not only affect the women themselves, the fetus and infant can also be affected through exposure to psychotropic drugs across the placenta or through breastfeeding, and side-effects potentially affect the mother’s ability to parent (eg, sedative drugs). However, concerns about risks to the fetus or a failure to titrate the dose through the pregnancy (to address the changes in drug concentrations) might lead clinicians to prescribe subtherapeutic doses.109
Figure 2
Guidelines to prescribe in the perinatal period
Adapted from The Maudsley prescribing guidelines (11th edn),108 by permission of David Taylor.
Risks to the fetus are difficult to assess because of the absence of RCTs and the resultant difficulties in interpretation of the evidence base. Many studies are small, with biased samples, low-quality study design, little adjustment for important confounders (such as smoking), and an almost invariable absence of adjustment for confounding by indication. Initial reports of risks have frequently not been substantiated or are shown to be smaller once larger studies and meta-analyses have been done. For example, despite early reports, a meta-analysis110 did not find an increased risk of spontaneous abortion associated with exposure to antidepressant drugs, and two large population studies111,112 (29 228 and 12 425 SSRI exposures, respectively) have not found associations with antenatal SSRIs and stillbirths or neonatal deaths after adjusting for confounders. Similarly, two meta-analyses113,114 showed paroxetine exposure is associated with only slightly increased risks of cardiac malformations (odds ratio [OR] 1·4) rather than the large ORs initially reported, and residual confounding is possible. Confounding by indication also needs to be considered—a study comparing outcomes in infants of women who stopped SSRIs before pregnancy and women who continued with SSRIs reported a similar increased risk of cardiac malformations in both groups,115 suggesting that the association is due to depression rather than the drug itself.
Antidepressant exposure in pregnancy is significantly associated with gestational age at birth (pooled mean difference in weeks, −0·45, 95% CI −0·64 to −0·25), preterm delivery (<37 or <36 weeks depending on the individual studies included; pooled OR 1·55, 95% CI 1·38–1·74), and Apgar score at 1 min (mean difference of −0·37 points) and 5 min (mean difference of −0·18 points), although some might be of restricted clinical significance.110 Meta-analyses have previously reported associations with birthweight, but no significant association with reduced birthweight was reported in the 2013 meta-analysis when the comparison group was limited to depressed mothers without antidepressant exposure.110
A consistent significant association exists between exposure to antidepressants during pregnancy and occurrence of poor neonatal adaptation syndrome (PNAS; OR 5·07, 95% CI 3·25–7·90), and individual clinical signs (respiratory distress, OR 2·20, 1·81–2·66; tremors, 7·89, 3·33–18·73).116 The use of observational study designs means causality cannot be inferred; the results could suggest measurement bias, selection bias, and confounding, but since abrupt discontinuation of antidepressants in adults is associated with withdrawal symptoms, infants might be at risk after birth. Whether the symptoms reflect withdrawal or toxicity is under debate. Symptoms noted are usually mild and self-limiting, but one study reported that infants who developed PNAS were at an increased risk of social-behavioural abnormalities even though they had normal cognitive ability.117Whether tapering of antidepressants the week before expected labour would reduce the occurrence of PNAS is unclear; some authors have argued that the balance of evidence suggests that discontinuation of clinically needed antidepressants in women near term is unwarranted because neonatal symptoms only occur in a small number of cases and are self-limited, but the risk to a woman’s mental health will be increased.109 Evidence on how long to observe the neonate for PNAS symptoms is scarce. If no symptoms emerge within the first 72 h after birth, PNAS is unlikely; when PNAS symptoms are present it is advisable to observe the infant until symptoms are resolved in case supportive treatment is needed.118
Some PNAS symptoms can suggest a spectrum of effects with mild respiratory signs potentially showing sub-clinical persistent pulmonary hypertension of the newborn (PPHN). A systematic review and meta-analysis119 reported an increased risk of PPHN associated with late pregnancy SSRI exposure (OR 2·50, 95% CI 1·32–4·73; absolute risk difference 2·9–3·5 per 1000 infants). Although individual studies used different diagnostic criteria and possible moderating variables such as caesarean section, body-mass index, or preterm delivery these could not be included in the meta-analysis. Serotonin has a role in the development and modulation of the lungs and this could be a factor in the development of PPHN. Evidence also shows that prenatal SSRIs are associated with neurobehavioural disturbances in early infancy including stress or pain regulation; the severity of these symptoms seems to be associated with high drug concentrations and pharmacogenetic metabolic factors.120
Fewer data exists for long-term outcomes of infants exposed to antidepressants in utero. However, studies are similarly difficult to interpret because of methodological problems and the known associations between maternal depression, impaired mother–infant interactions, and adverse infant or child outcomes.50 Some studies reported a range of normal neurodevelopmental outcomes including cognitive, behavioural, and emotional outcomes while also noting adverse outcomes (eg, behavioural problems measured by the strengths and difficulties questionnaire121) in children exposed to maternal depression in utero in the comparison groups,122,123,124 but others have reported small delays in developmental milestones in children exposed to antidepressants in utero. A study125 using Danish National Cohort data reported that 415 children exposed in the second or third trimester in utero to antidepressants sat 15·9 days (95% CI 6·8–25·0) and walked 28·9 days (95% CI 15·0–42·7) later than children who were not exposed to antidepressants (although still within the normal range of development); fewer children with exposure to antidepressants in utero were able to sit without support aged 6 months (OR 2·1, 95% CI 1·23–3·60), and fewer were able to occupy themselves aged 19 months (2·1, 1·09–4·02) than children who were not exposed.125 A study of 31 infants exposed prenatally to SSRIs scored significantly lower than the 52 non-exposed infants on gross motor (p=0·03), social-emotional (p=0·04), and adaptive behaviour (p=0·05) subscales of the Bayley Scale of Infant Development.126 Two nested case-control studies have reported an association between antidepressant exposure in pregnancy and autism spectrum disorders,127,128but no significant association was shown in a large cohort study.129
Although most studies focus on adverse outcomes with some inconsistent results, there is new evidence, albeit with small samples, that SSRI use in pregnancy could have a positive effect. For example, prenatal antidepressant treatment mitigates the effect of maternal anxiety on P50 sensory gating (associated with increased vulnerability to attentional deficits),130 and infants exposed to SSRIs in utero show more readiness to interact during a toy session than do a non-SSRI group exposed to high levels of maternal depressive symptoms.131 Prenatal antidepressant exposure might account for some neurobehavioural outcomes in early childhood, but maternal and infant genetic and environmental factors (including maternal depressive symptoms in pregnancy and the postnatal environment) will also shape childhood behaviours.50,120
Antidepressant exposure in breastfed infants is lower by five to ten times than is exposure in utero. The milk drug concentration can be used to estimate the daily drug dose ingested by the infant, assuming an average milk intake of 150 mL/kg bodyweight per day.132 The infant dose per kg can be expressed as a percentage of the maternal dose per kg and a relative infant dose of less than 10% is deemed a negligible exposure. A review132 reported low relative infant doses for fluvoxamine, paroxetine, sertraline, duloxetine, reboxetine, bupropion, and mirtazapine, and an earlier review133reported a low relative infant dose for nortriptyline. Relative infant doses around 10%, and in some cases higher than 10% for citalopram, fluoxetine, and venlafaxine, with somewhat lower relative infant dose for escitalopram have been reported.132 When high concentrations have been reported, infants have been aged younger than 3–4 months, when infants are still developing hepatic function. Metabolic capacity is not well developed in preterm babies and those with genetically determined impairment in antidepressant metabolism via cytochrome P-450 enzymes (CYP2D6 and CYP2C19).132Reassuringly, indirect biological evidence shows that serotonin transmitters are not affected because no platelet serotonin effects are noted in infants of breastfeeding mothers treated with sertraline or fluoxetine.134
Some adverse but non-specific events in infants exposed to antidepressants via breast milk have been reported in case reports and case series, more often after exposure to fluoxetine (eg, irritability and poor feeding) and citalopram (eg, poor sleep) than after exposure to other drugs.132 Respiratory depression, hypotonia, and vomiting have been associated with the tricyclic doxepin. No studies have identified an increased risk of adverse long-term outcomes. Most authors conclude that if a mother was successfully treated for depression during her pregnancy, the same drug should usually be used in the post-partum period because discontinuation or switching of an antidepressant treatment could lead to relapse.
Perinatal mental disorders are common and can adversely affect the mother and infant. However, they are treatable and should therefore be identified early to prevent adverse long-term effects. Where possible, non-pharmacological treatments should be used but in more severe cases, effective doses of antidepressants will be needed after a careful collaborative analysis of the ratio of risk versus benefit.