A rise in stillbirths between April and June, at the peak of the coronavirus pandemic, has prompted a national review by a patient safety body in England.
During that period, there were 40 stillbirths after labour began, compared with 24 in the same period last year.
The Healthcare Safety Investigation Branch will release its report in 2021.
Pregnancy and childbirth experts say women may have delayed seeking care.
The Royal College of Obstetricians and Gynaecologists said the figures were "concerning" but it is waiting for more data from after the pandemic to compare numbers of stillbirths over a longer timeframe.
The Office for National Statistics is due to release more up-to-date figures soon.
The HSIB told the Health Service Journal that it had seen approximately twice the number of intrapartum stillbirths compared to the same time last year.
Intrapartum care covers the start of labour up to the birth of a baby.
RCOG president Dr Edward Morris said antenatal care was "essential" and encouraged all women to attend appointments.
In a survey of nearly half of maternity units, 86% said fewer heavily pregnant women than normal had come forward with emergency issues in April, during lockdown.
"This may have been due to confusion around whether these appointments are essential, fear of attending a hospital or not wanting to burden the NHS," Dr Morris said.
"We have consistently advised women who have concerns or worries about their or their baby's health – including the baby's movements – should seek medical advice from their midwife or hospital immediately."
The RCOG is also carrying out a national investigation of the "potential indirect effects of Covid-19 on pregnancy outcomes" before and after childbirth.
In the meantime, it is urging hospitals to avoid redeploying maternity staff during the second wave of the pandemic.
Stillbirth rates in England reached their lowest level on record in 2018, at four per 1,000 births (or 2,520 stillbirths), down from five in 1,000 in 2010.
By 2025, the government wants to reduce stillbirths further – to 2.6 per 1,000.