Prenatal testing among women pregnant after assisted reproductive techniques in Denmark 1995-2000: a national cohort study

BACKGROUND: Women pregnant after assisted reproductive techniques (ART) are generally older than women with spontaneously conceived pregnancies, and are consequently more likely to carry a child affected by a chromosomal disorder. Furthermore, a significantly increased rate of chromosomal abnormalities after intracytoplasmatic sperm injection (ICSI) has been reported. The aim of this study was to describe the use and results of prenatal invasive diagnostic testing in a national Danish cohort of in vitro fertilization (IVF)/ICSI pregnancies. Additionally, we examined to what extent second trimester serum screening was used.

METHODS: We used a register-based cohort study including all ongoing clinical pregnancies achieved by IVF/ICSI in 1995-2000 in Denmark. Data on fertility treatment, pregnancy and pregnancy outcome together with data on cytogenic testing and the use of triple test were retrieved from national statutory registers. Data on the invasive testing rate among the general Danish population were retrieved from the same national registers.

RESULTS: In this 6 year period, 8531 ART pregnancies were recorded representing an unselected national ART population (6122 IVF, 2087 ICSI and 322 'IVFICSI'). The number of prenatal invasive procedures was relatively low, 16.3%, and the uptake of second trimester serum screening was very low, 7.4%. The invasive testing rate, corrected for advanced maternal age distribution, was lower in the study population than in the general population. The rate of karyotype aberrations detected by prenatal testing was 2.7% (43/1586), whereas the overall rate of pre- and post-natally detected aberrations was 0.6% (62/9625). Chromosome aberrations were more common in the ICSI-treated group compared with the IVF-treated group [1.3% (30/2297) versus 0.5% (32/6957), P < 0.0001]. This was also the case if only prenatally diagnosed chromosome aberrations were compared [4.3% (24/556) versus 1.9% (19/975), respectively, P < 0.01].

CONCLUSIONS: ART pregnancies represent a group of high-risk pregnancies with regard to chromosomal aberrations, but nevertheless their uptake of prenatal testing was low. ICSI pregnancies compared with IVF pregnancies had a higher rate of chromosomal abnormalities, even though the average maternal age was lower.