Midwives have raised concerns over the small numbers of women who are getting "continuity of carer" throughout their pregnancy, birth and aftercare.
Only a "small minority" of health bodies across England, Scotland and Wales are providing women with this service, a new audit has found.
Despite the issue being a key theme raised by national maternity reviews, only 15% of trusts and boards reported that women see the same midwife for most care contacts in the antenatal, intrapartum and postnatal period, including care in labour from a known midwife.
The Royal College of Midwives (RCM) said the figure was "worrying", saying that continuity helps to ensure safe, high-quality care.
The National Maternity and Perinatal Audit (NMPA), conducted by experts from the Royal College of Obstetricians and Gynaecologists (RCOG), the RCM, the Royal College of Paediatrics and Child Health (RCPCH) and the London School of Hygiene & Tropical Medicine, also raised concerns over staffing - particularly among middle grade doctors, or registrars, and the number of midwives on antenatal and postnatal wards.
The average number of beds per rostered midwives on these wards - which care for women who need to be in hospital before and after birth - was seven.
But in some units, midwives are caring for as many as 16 women on these wards at once.
The report, based on survey responses from all NHS trusts and health boards, also found that 88% of obstetric units reported a gap in their middle grade rota.
Other key themes of the report include:
:: Only a tenth of trusts and boards said that women themselves have access to their electronic maternity record.
:: 45% of obstetric units, 27% of alongside midwife-led units and 23% of freestanding midwife-led units closed at least once in the last year because they did not have enough staff or beds to safely care for any more women.
:: Of the sites which monitor one-to-one midwifery care during labour, it was found that the vast majority (95%) receive this.
Commenting on the report, Mandy Forrester, head of quality and standards at the RCM, said: "There is much to be optimistic about, but it also throws up some issues of real concern.
"It is worrying that so few women are seeing the same midwife or group of midwives. Continuity of carer is crucial to ensuring safe, high-quality care.
"Another concern is that so many women cannot get access to their electronic pregnancy records; this disempowers women and needs urgent attention.
"Maternity unit closures are also very worrying and will not solve the shortage of midwives in England.
"When a situation arises where a maternity unit has not enough staff and/or beds to care for women safely, the decision might be made to temporarily close the unit to new admissions and the RCM supports this.
"However, such closures can last from a few hours to several days or more, with women who were booked to give birth in a particular unit then diverted to other units and this situation can be very unsettling for women.
"Also, if units are regularly and persistently having to close their doors it suggests there is an underlying problem around capacity and staffing levels that needs immediate attention."
Professor Lesley Regan, president of RCOG, said: "While the results show some promising developments, it also highlights where improvements must and should be made - for example, ensuring all women can choose from the full range of birth settings, have continuity of care during pregnancy and access to their electronic maternity records.
"The difficulties in securing staffing in obstetric units is particularly worrying. Moving forward, it is anticipated that rota gaps will persist and worsen in most units.
"The pressures on maternity services are growing which could compromise the experience for women and their families.
"Stretched and understaffed services also affect the quality of care provided to both mothers and babies.
"If the UK governments are serious about improving the safety of maternity services, these staffing and capacity issues must be addressed as a matter of urgency."
A spokeswoman for NHS England said: "This report shows the NHS is stepping up its game delivering more personalised choice and joined-up care with better team-working as well as importantly looking at a number of ways to improve continuity of care for new mums.
"There's no 'one size fits all' approach to maternity care and the report will act as an important benchmark for local areas helping identify where improvements can be made including ensuring the right staffing levels for the women and babies they care for."
Scotland's Public Health Minister Aileen Campbell MSP said: "I welcome the report by the NMPA team, which provides a comprehensive snapshot of the current organisation of maternity and neonatal services in the UK.
The NHS already provides an exceptional maternal and neonatal service to thousands of women and babies across Scotland every year.
"We are committed to moving forward with implementation of the recommendations in 'The Best Start' report of our Review of Maternity and Neonatal Services, and those recommendations are consistent with the themes in the NMPA Report."
A Welsh Government spokeswoman added: "We welcome the report and will study it closely."