The influence of smoking on the pregnancy-associated plasma protein A, free beta human chorionic gonadotrophin and nuchal translucency.

OBJECTIVE: To analyse the effects of smoking on first trimester parameters used in prenatal screening for Down's Syndrome. DESIGN: A chart study. SETTING: Primary care centres and maternity clinics of the participating universities' and central hospitals. POPULATION: Three thousand and one hundred fifteen women screened by nuchal translucency measurement and 4436 women screened by maternal serum samples. Only normal singleton pregnancies were included. METHODS: The mean multiples of median of pregnancy associated plasma protein A (PAPP-A), free beta human chorionic gonadotrophin (beta-hCG) and nuchal translucency were compared by independent samples t test after logarithmic transformation of the data between smokers and non-smokers. MAIN OUTCOME MEASURES: PAPP-A and free beta-hCG concentrations and nuchal translucency measurements. RESULTS: PAPP-A was significantly reduced and nuchal translucency increased if the mother smoked. The smokers were more frequently considered as being at high risk for Down's Syndrome. CONCLUSIONS: Correcting PAPP-A median for smokers down by 20% might improve the accuracy of the risk evaluations given to individual women. If the association between increased nuchal translucency and smoking can be confirmed, it poses interesting questions as to the reasons for increased nuchal translucency among normal pregnancies.

Maternal serum human chorionic gonadotrophin and pregnancy-associated plasma protein A in twin pregnancies in the first trimester.

OBJECTIVES: To determine the levels of free beta-human chorionic gonadotrophin (beta-hCG) and pregnancy-associated plasma protein A (PAPP-A) in twin pregnancies in the first trimester. METHODS: Serum samples were obtained from 67 pregnant women with twin pregnancies and maternal serum free beta-hCG and PAPP-A concentrations were compared with those of 4279 singleton controls between the 8th and 13th weeks of gestation. RESULTS: The geometric means of chromosomally normal twin pregnancies were 1.85 MoM for free beta-hCG and 2.36 MoM for PAPP-A. There were no cases affected by Down syndrome in either group. CONCLUSION: Twin pregnancies secrete more PAPP-A than expected on the basis of singleton controls whereas free beta-hCG production is not increased. The results of the present study can be used to establish normal reference values when introducing first trimester Down syndrome screening in prenatal care.