Smallest and largest fetuses at greater risk of being stillborn, research finds

June 25, 2012

The tiniest and the heaviest fetuses are at much higher risk of being stillborn than those of average weight, new research has found.

Fetuses who are "severely small for ," or weigh below the bottom one percentile of all fetuses, disproportionately account for about six per cent of all , according to researchers at St. Michael's Hospital.

Fetuses that are "severely large for gestational age," or weigh above the 99th percentile, account for nearly one per cent of stillbirths.

"In this study of all registered liveborn and infants in Ontario, extreme underweight and overweight states confer the highest risk of stillbirth," said Drs. Joel Ray and Marcelo Urquia, authors of the paper that appears in the current issue of the Journal of Perinatology.

Stillbirth is traditionally defined as the death of a fetus at more than 23 weeks of gestation weighing 500 grams or more. However, Drs. Ray and Urquia included babies born starting as early as 20 weeks of gestation on the grounds that maternal-fetal bonding is well established at that point, since most mothers-to-be have undergone a Level 2 ultrasound detailing the unborn baby's developing bones and organs.

Including those babies provides new information about the degree to which low and high weights are associated with stillbirths, including those before the point of viability, Dr. Ray said. That, in turn, may help doctors better decide at which time point it is better to allow a pregnancy to continue so the fetus can grow, or to deliver a who might otherwise die in the womb.

The rate of stillbirths in industrialized countries is about six per 1,000, of which half occur after 27 weeks of gestation. In poorer countries, the rate is up to five times higher. Stillbirths are more common than the death of a baby after birth, such as from or as a result of . Yet, stillbirths have largely been ignored by our society, especially in terms of their emotional effect on the mother, her partner and extended family, Dr. Ray said.

The researchers examined records of all 767,016 live births and all 4,697 stillbirths in Ontario between 2002 and 2007. They said that because they looked at so many births, they could also make statistically precise estimations of the impact of extremely low birthweight on the risk of stillbirth.

They found that 19 per cent of stillbirths occur in fetuses under the tenth percentile of weight. But being below the first percentile of weight meant the fetus faced a 9.5 times higher risk of being stillborn than babies who are within the average weight range, between the 40th to 60th weight percentiles.

Dr. Ray said that when fetuses are severely small for gestational age, it usually means there is a problem with the placenta. Fetuses who are severely large for gestational age generally so because of the mom having diabetes or obesity.

The authors conclude that since more than 95 per cent of women in the industrialized world receive a Level 2 anatomical ultrasound before 22 weeks gestation, fetal weight should be estimated and reported at this time of the ultrasound, as a standard practice. In doing so, the early presence of a small or large fetus may help guide ongoing ultrasound surveillance for growth and well-being.

Explore further: Stillbirth risk affected by mother's sleep position

Related Stories

Stillbirth risk affected by mother's sleep position

June 16, 2011
(PhysOrg.com) -- In a new study published in the British Medical Journal, Tomasina Stacey from the University of Auckland’s Department of Obstetrics and Gynecology revealed that women who do not sleep on their left side ...

Slow-growing babies more likely in normal-weight women; Less common in obese pregnancies

April 27, 2012
Obesity during pregnancy puts women at higher risk of a multitude of challenges. But, according to a new study presented earlier this month at the American Institute of Ultrasound in Medicine annual convention, fetal growth ...

Pregnant women advised to stay cool for baby's sake

December 15, 2011
Queensland University of Technology (QUT) world-first research has found a link between increases in temperature and the incidence of stillbirth and shorter pregnancies.

Many babies born to immigrants are being labeled too small incorrectly

February 15, 2012
One of the first things people ask new parents is how much does their baby weigh.

Studies identify most common causes, risk factors for stillbirth

December 13, 2011
Common causes for stillbirth include obstetric complications and placental abnormalities, while factors that could be known at the start of pregnancy, such as previous stillbirth or pregnancy loss, were associated with an ...

Blood test for pregnant women could predict risk of having dangerously small babies

June 21, 2012
Researchers from the Ottawa Hospital Research Institute (OHRI) and the University of Ottawa (uOttawa) have found a protein in the blood of pregnant women that can predict if they are likely to have a fetus that doesn't grow ...

Recommended for you

Hope for couples suffering IVF miscarriage

September 20, 2017
Women who miscarry during their first full round of IVF are more likely to have a baby after further treatment than women who don't get pregnant at all.

Does mother's mental health affect pregnancy?

September 13, 2017
(HealthDay)—Three common mental health disorders—depression, panic disorder and generalized anxiety disorder—pose no serious threat to pregnant women or the health of their babies, a new study finds.

Preeclampsia may boost heart disease risk by altering blood vessels

September 12, 2017
Preeclampsia may permanently change the blood vessels of women who experience the condition during pregnancy, boosting their lifelong risk for cardiovascular disease, according to Penn State researchers.

Discovery of genes linked to preterm birth in landmark study

September 6, 2017
A massive DNA analysis of pregnant women has identified six gene regions that influence the length of pregnancy and the timing of birth. The findings, published today in the New England Journal of Medicine, may lead to new ...

Older wombs linked to complications in pregnant mice

September 5, 2017
Deciding to start a family later in life could be about more than just the age of your eggs. A new study in mice suggests the age of a mother's womb may also have a part to play. This work, led by Dr Myriam Hemberger at the ...

Study suggests simple way to predict preterm births

September 4, 2017
Up to 18 percent of babies born worldwide arrive before they are full-term, defined as 37 weeks of gestation. About 1 million of those babies do not survive, and those who do can face developmental problems such as impaired ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.