BJOG Release: Smoking Obscures Tests For Down Syndrome, UK

Main Category: Pregnancy / Obstetrics
Also Included In: Smoking / Quit Smoking;  Women's Health / Gynecology;  Pediatrics / Children's Health
Article Date: 26 Nov 2007 - 6:00 PDT

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New research published in BJOG: An International Journal of Obstetrics and Gynaecology shows that women smoking during the first stage of pregnancy affects the levels of chemicals in the blood that are used for Down syndrome screening, and this could lead to misleading results.

Researchers from Saudi Arabia carried out tests on 2, 337 fit and healthy first-time mothers in the first trimester of pregnancy, from 2001 - 04. The women were asked about their smoking habits and classified as smokers if they smoked one or more cigarettes or sheeshas a day. Sheesha smoking (also known as hubli bubli or hookah) is a traditional form of smoking where smoke is passed through water in an enclosed glass container and inhaled through a pipe. It is a common pastime in many Middle Eastern countries. This is the first study on the effect of sheesha smoking on pregnant women.

The tests for Down syndrome - fetal nuchal translucency thickness (fetal NT), maternal serum free beta-human chorionic gonadotropin (free â-hCG) and pregnancy- associated plasma protein-A (PAPP-A) - were carried out between 11 weeks and 13 weeks 6 days of gestation.

Fetal NT is done using an ultrasound scan to check on the levels of fluid behind the fetus' neck. A higher level of fluid indicates a risk of Down syndrome. Free âhCG is a hormone present during pregnancy and PAPP-A is a protein present during pregnancy. Measurements of free â-hCG and PAPP-A are taken from blood samples.

Results show that serum cortinine levels (nicotine in the blood) levels were significantly higher in smokers than non-smokers, with the highest levels in sheesha smokers. This is because of the higher tobacco content in sheesha. Compared to non-smokers, smokers of cigarettes and sheesha had lower levels of free â-hCG and PAPP-A and higher levels of fetal NT, which would in non-smokers indicate a higher risk of Down syndrome.

According to researchers, this study matches the findings of other studies of pregnant women smoking in other countries, although it should be borne in mind that genetic and nutritional factors can also affect the results. The researchers suggest that it is the damaging effect of smoking on the developing placenta that results in changes in the mother's biochemical markers.

Based on the evidence uncovered, the researchers conclude that the changes in fetal NT and the biochemical markers in smoking pregnant women mean that that screening is less effective in this group; using standards adjusted for the effects of smoking might improve the accuracy of prediction to the level in non-smokers

Professor Philip Steer, BJOG editor in chief said "The effects of smoking during pregnancy are well documented. Babies of mothers who smoke during pregnancy are small for gestational age and tend also to deliver earlier. This research indicates that smoking may also cause overestimation of the risk of Down syndrome, thus exposing the mother to a higher risk of an unnecessary amniocentesis."

"Are the dangers of smoking during pregnancy hokum? Definitely not, especially it seems, if you're smoking a hookah."

Note

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 Blackwell Publishing. 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

Ardawi M, Nasrat H, Rouzi A, Qari M, Al-Qahtani M, Abuzenadah A. The effect of cigarette or sheesha smoking on first-trimester markers of Down syndrome. BJOG 2007;114:1397-1401.

Royal College of Obstetricians and Gynaecologists