Here we describe the insights gained from sequencing the whole genomes of 2,636 Icelanders to a median depth of 20×. We found 20 million SNPs and 1.5 million insertions-deletions (indels). We describe the density and frequency spectra of sequence variants in relation to their functional annotation, gene position, pathway and conservation score. We demonstrate an excess of homozygosity and rare protein-coding variants in Iceland. We imputed these variants into 104,220 individuals down to a minor allele frequency of 0.1% and found a recessive frameshift mutation in MYL4 that causes early-onset atrial fibrillation, several mutations in ABCB4 that increase risk of liver diseases and an intronic variant in GNAS associating with increased thyroid-stimulating hormone levels when maternally inherited. These data provide a study design that can be used to determine how variation in the sequence of the human genome gives rise to human diversity.

Introduction: The rate of cesarean section (CS) for non-medical reasons has risen and is a concern for health care. Women's preferences may vary across countries for psychosocial or obstetric reasons.Methods: A prospective cohort study of 6,549 women in routine antenatal care, giving birth in Belgium, Iceland, Denmark, Estonia, Norway or Sweden. Preference for mode of birth was self-reported in mid-pregnancy. Birth outcome data were collected from hospital records.Results: A CS was preferred by 3.5% of primiparous women and 8.7% of the multiparous women. Preference for CS was associated with severe fear of childbirth, with a negative birth experience in multiparous women, and with depressive symptoms in the primiparous. Women were somewhat more prone to prefer a cesarean in Iceland, OR 1.70(1.02-2.83), adjusted for age, education, depression, fear of childbirth, history of abuse, previous cesarean and previous negative birth experience. Out of the 404 women who preferred CS during pregnancy, 286 (70.8%) were delivered by CS, mostly for a medical indication. A total of 9% of the cesareans in the cohort had a non-medical indication only.Conclusions: Women's preference for cesarean section often seems to be due to health concerns. Both medical and psychological factors need to be addressed in antenatal counseling. Obstetricians need to convey accurately to women the risks and benefits of CS in her specific case. Maternity professionals should identify and explore psychosocial reasons for women's preferences.