 Smoking During Pregnancy Leads to Smaller Babies
Source: medicalnewstoday.com Date: 05/12/08
New research to be published in BJOG: An International Journal of Obstetrics and Gynaecology has found significant association between smoking during pregnancy,
endothelial
dysfunction and growth restriction in the unborn baby. Endothelial
dysfunction can lead to reduced dilation of blood vessels, inflammation
of the vascular wall and an increase in the incidence of blood clots.
The University of Sydney study included 41 pregnant women, 21 of whom
smoked ten or more cigarettes a day and 20 who were non-smokers. The
women were studied between week 28 and week 32 of their pregnancy and
for those who smoked, the average number of cigarettes per day was 15.7
+/- 4.9.
Endothelial function is responsible for modulating vascular tone,
vessel size and regulation of blood flow and in this study it was
assessed by the ultrasound technique flow-mediated dilatation (FMD).
This tests the main blood vessel of the upper arm, the brachial artery,
by measuring its diameter following induced reactive hyperemia - when
blood collects in an organ of the body because of a blockage in the
veins that move the blood out.
The smokers in the group were asked to refrain from cigarettes from
midnight before the test commenced at nine am. After 10 minutes of
rest, a blood pressure cuff was placed on the lower arm and inflated
for five minutes to cause reactive hyperemia. At the completion of the
test the women had a 10 to 15 minute break during which time the
smokers could choose to have none, one or two cigarettes. The test was
then repeated on all the women.
Results showed that the women who smoked during pregnancy had
persistent endothelial dysfunction which remained at a constant level
whether one or two cigarettes had just been smoked or following a
nine-hour break from smoking. The study also found strong links between
endothelial dysfunction and intrauterine growth restriction, which
carries an increased risk of perinatal mortality and morbidity.
Although gestational age was similar in both groups, birth weight was
significantly reduced in the smokers with 38% (8/21) of babies at less
than the 10th percentile and 24% (5/21) less than the 5th percentile.
Those babies whose birth weight was less than the 10th percentile were
born to mothers with a significantly lower endothelial function (4.7
+/- 2.2 compared to 7.3 +/- 4.6). There were no small-for-gestational
age babies in the non-smoking group.
Ann Quinton, senior research sonographer, said "Our work provides
evidence that smoking has a direct and long term deleterious effect on
vascular function in pregnancy and thus provides evidence to why babies
of smokers are growth restricted."
Professor Philip Steer, BJOG editor-in-chief said, "There is extensive
evidence that women who smoke during pregnancy do so at great risk to
themselves and to their baby. Smoking is linked to miscarriage,
premature birth, placental abruption and placenta praevia - all very
serious conditions indeed.
"This research is further proof that pregnant women must stop smoking
to ensure that their babies have the healthiest start. Women should
speak with their midwife, GP or local PCT who will be able to provide
important information and support while they break the habit".
Notes
BJOG: An International Journal of Obstetrics and Gynaecology is owned
by the Royal College of Obstetricians and Gynaecologists (RCOG) but is
editorially independent and published monthly by Wiley-Blackwell. The
journal features original, peer-reviewed, high-quality medical research
in all areas of obstetrics and gynaecology worldwide. Please quote
'BJOG' or 'BJOG: An International Journal of Obstetrics and
Gynaecology' when referring to the journal.
Reference
The relationship between cigarette smoking, endothelial function and intrauterine growth restriction in human pregnancy.
Quinton A, Cook C, Peek M.
BJOG 2008;115:780-84 DOI: 10.1111/j.1471-0528.2008.01691.x.
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