Warning over "drug dependent" baby figures
Morphine and methadone were among substances given to babies with neonatal abstinence syndrome to wean them from drugs used in pregnancy by their mothers.
But experts fear the true scale of the issue is likely to be greater, because many are born with drug dependency will not require medication.
Dr Alison Wright, spokeswoman for the Royal College of Obstetricians and Gynaecologists, said substance use during pregnancy could have a serious impact on the health and bonding of mother and baby.
She acknowledged that "complex barriers" stood in the way of mothers-to-be disclosing their drug use but urged women to seek help.
Dr Wright said: “We would encourage all pregnant women who use recreational drugs to speak to their GP, obstetrician or midwife, who will be able to offer non-judgemental and appropriate advice, help and support."
Sharon Mallett, director of nursing at drug, alcohol and mental health charity We Are With You, said drug-using mothers often experienced "overwhelming guilt and shame" and called for midwives and other experts to work together to create non-judgemental environments.
She added: "The earlier parents seek support the more positive the results are for both the mother and child. That’s why it’s really important not to judge mothers who do come forward around this issue."