Objective Serotonin reuptake inhibitor (SRI) antidepressant use in pregnancy has been associated with increased risks of low birth weight, preterm birth, persistent pulmonary hypertension and neurobehavioural disturbances; however, the impact on the fetal physiology remains extremely limited.

Methods Fetal heart rate (FHR) and blood flow measurements were obtained in the morning (08:00 hours) and afternoon (13:00 hours) from mothers at 36 weeks gestation treated with an SRI (exposed; n  =  11) and healthy mothers (non-exposed; n  =  21). FHR was monitored using an Oxford Sonicaid System 8002. Doppler blood flow velocity waveforms in the middle cerebral artery (MCA), uterine and umbilical arteries and fetal right pulmonary artery, were done using an Aloka Prosound 5500 scanner.

Results FHR accelerations in the exposed fetuses were significantly less than in the non-exposed fetuses during both sessions. Accelerations significantly increased from the morning to afternoon session in the non-exposed fetuses but did not occur in the exposed fetuses. MCA pulsatility index (PI) was significantly lower in the exposed fetuses in the morning only. This was due to a significant decrease in PI in the non-exposed fetuses in the afternoon that did not occur in the exposed fetuses. Similar findings were obtained with the MCA resistance index and S/D ratio. Third trimester maternal depressed mood was also controlled for in the analyses.

Conclusions Human fetal exposure to SRI reduces FHR accelerations and MCA resistance, which may be due to alterations in brain function, and attenuates the alterations in both variables that occur during the day in non-exposed fetuses.