Some 71% of GPs said they had seen an increase in young mothers seeking help with problems such as postnatal depression, sleep disorders and feeding problems.
The country's largest union, Unite, said that the figures highlighted the current crisis caused by cutbacks in health visitor jobs.
It pointed to the latest NHS workforce statistics, which revealed that a full-time health visitor job was being lost every 27 hours.
Some GPs said they felt ill-qualified to offer young mothers advice and others warned they could not fill the health visitors' child protection role.
Unite's lead professional officer for strategy and practice development, Cheryll Adams, commented: "We welcome the new GP findings in as much that it gives further evidence to our campaign to restore the UK's health visiting service for the benefit of families and communities.
"We are unsurprised by the effects of health visitor cuts on GP workloads with young families, as this was predicted four years ago when the serious cuts started."
She added: "Health visitors also started to be moved out of GP surgeries to work in neighbourhood-based teams. This trend has made the vital communication between doctors and health visitors more difficult."