Risk factors predisposing to fetal loss following a second trimester amniocentesis.

OBJECTIVE: To examine the influence of possible risk factors on fetal loss rate following amniocentesis. DESIGN: Retrospective analysis of case records between 1993 and 1998. SETTING: Fetal medicine unit of a large teaching hospital. POPULATION: One thousand and six women with singleton pregnancies formed the study group. Seven hundred and eight of them had bleeding during the current pregnancy before the procedure. while 298 had a history of three or more first trimester abortions and/or a second trimester miscarriage or termination of pregnancy. Four thousand and twenty-four women who had amniocentesis and had no risk factors served as controls. Both groups were also classified according to maternal age. Group 1:1,610 women aged 20-34 years; Group 2: 2850 women aged 35-39 years; Group 3; 570 women > 40 years. METHODS: Women of both groups underwent a second trimester amniocentesis between 16 and 21 weeks of gestation. Fetal losses following amniocentesis were examined in three time intervals: 1. in the first two weeks after the procedure; 2. up to the 28th week; 3. from the 28th week to term. RESULTS: There was a statistically significant difference in the fetal loss rate between women aged 20-34 years (2.54%) and those > 40 years (5.1%). Women with a history of vaginal bleeding during the current pregnancy had a higher fetal loss rate compared with controls (6.5% vs 2.8%), which corresponds to an odds ratio of 2.4 (95% CI 1.69-3.42). A similar difference was found between the group of women with a history of previous abortions/terminations and the controls (8% vs 2.8%): OR 3.03 (95% Cl 1.92-4.79). CONCLUSIONS: There is a higher risk of fetal loss following amniocentesis in women > 40 years of age compared with those aged 20-34 years. Bleeding in the current pregnancy, a history of three or more first trimester abortions, a second trimester miscarriage or termination of pregnancy seem to be significant predisposing factors for fetal loss after an amniocentesis.

False positive serum biochemical screening and subsequent fetal loss in women less than 35 years of age.

OBJECTIVE: To examine the fetal loss rate in women younger than 35 years of age following a false positive serum biochemical screening. DESIGN: Retrospective analysis of case records between 1991 and 1998. SETTING: Fetal medicine unit of a large teaching hospital. POPULATION: Four hundred and fifty-six women with singleton pregnancies and false positive serum biochemical screening for Down's Syndrome (study group). Nine hundred and twelve matched controls with true negative serum biochemical screening (control group). METHODS: Women of both groups had a second trimester serum screening for Down's Syndrome using alpha fetoprotein, human chorionic gonadotrophin (hCG) and unconjugated oestriol (uE3); and they also underwent genetic amniocentesis. RESULTS: The overall fetal loss rate in the study group was 5.3% (24/456), compared with 1.65% (15/912) in the control group RR 3.2, 95% CI 1.7-5.99; P < 0.001). The majority of fetal losses in the study group occurred after 28 weeks, while in the controls this happened between 24 and 28 weeks of gestation. CONCLUSIONS: A false positive serum biochemical screening in women under 35 years of age is associated with a threefold increased risk of subsequent fetal loss. However, most of fetal losses in this group occurred after 28 weeks, indicating that intensive antepartum fetal surveillance could improve the perinatal outcome.