The Care Quality Commission (CQC) said that some women who'd been booked in at the Wakefield site's birth centre were experiencing "significant delays", as it prepares to take on more mums-to-be.
Pinderfields may have to accommodate more births next year, as a result of the proposed closure of the maternity unit at Pontefract Hospital.
The Mid Yorkshire NHS Hospitals Trust, which runs both sites, said in October that the Friarwood Birth Centre at Pontefract was being "grossly" underused, as it explained the reasons behind the move, which has not yet been given final approval.
But in contrast to Pinderfields, the CQC has rated maternity services at Pontefract as 'good'.
In their report, following a visit in the summer, inspectors said the trust employed "sufficient" numbers of midwives but they were not convinced that they were deployed correctly.
With direct reference to Pinderfields, they added: "We saw high proportions of women booked for planned inductions of labour experienced significant delays."
The report went on to say that some of these women were waiting at least 24 hours for the appropriate care and that there were issues with antenatal care.
Although the trust was praised for its "kind and caring" attitude towards mums-to-be, the report added: "During our inspection, some staff raised concerns about capacity and workload, which impacted on their perceptions of culture within the service."
Councillors have repeatedly expressed concerns about what impact closing the Friarwood Birth Centre will have on Pinderfields.
Trust bosses have insisted that Pinderfields can cope with the extra demand, citing figures that show it accommodates nearly 6,000 births a year, compared to fewer than 200 at Pontefract.
But at a meeting in November, MP Yvette Cooper accused the organisation of "not being straight with the public" about the issue, and said that those figures had been influenced by repeat temporary closures at Pontefract.
But the Pontefract maternity unit was praised by inspectors for typically achieving "good outcomes" for mums and babies.
Their report said that the service, "received a comparitively low number of complaints and a relatively high number of compliments" from patients.
The trust was contacted for comment.
Its entire service was rated 'requires improvement' following the CQC's month-long inspection last summer.
Local Democracy Reporting Service