Taking anti-psychotic drugs during pregnancy increases the risk of premature delivery, respiratory problems and withdrawal symptoms in babies, a new study by the Monash University shows.

Anti-psychotic drugs are used to treat mental conditions such as schizophrenia, major depression and bipolar disorder.

"There's been little research on antipsychotic medication during pregnancy and if it affects babies. The lack of data has made it very difficult for clinicians to say anything conclusively on how safe it is for babies," lead study author Jayashri Kulkarni said in a news release.

For the study, the researchers examined 147 women enrolled in the National Register of Anti-psychotic Medications in Pregnancy. The participants were interviewed every six weeks during pregnancy and were followed till their babies were one year old.

The study findings revealed that 18 percent babies were born prematurely, 37 had respiratory distress and 15 percent had withdrawal symptoms.

"This new research confirms that most babies are born healthy, but many experience neonatal problems such as respiratory distress," Kulkarni said.

The research team said that low doses of anti-psychotic drugs do not cause harm to the babies but large doses of the drugs affect greatly.

A recent study about why baby girls survive more than baby boys showed an association between placenta and the chances of survival. The study researchers said that there was a sex bias in the regulation of genes in the human placenta. The findings revealed that female babies have more expression of genes involved in placental development, the maintenance of pregnancy and maternal immune tolerance, researchers at the University of Adelaide explained.

The current study is published in the journal PLOS ONE.