1999/07/01 by David B. Dunson, Donna D. Baird, Allen J. Wilcox +1 · 4 citations
Medicine · #Ovarian function and disorders #Assisted Reproductive Technology and Twin Pregnancy #Reproductive Health and Technologies
paper · pdf · doi:10.1093/humrep/14.7.1835
openalex publication_date 1999/07/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/18
Two studies have related the timing of sexual intercourse (relative to ovulation) to day-specific fecundability. The first was a study of Catholic couples practising natural family planning in London in the 1950s and 1960s and the second was of North Carolina couples attempting to become pregnant in the early 1980s. The former identified ovulation based on the ovulatory shift in the basal body temperature, while the latter used urinary assays of hormones. We use a statistical model to correct for error in identifying ovulation and to re-estimate the length of the fertile window and day-specific fecundabilities. We estimate the same 6-day fertile interval in both studies after controlling for error. After adjusting for error both data sets showed the highest estimate of the probability of pregnancy on the day prior to ovulation and both fell close to zero after ovulation. Given that the fertile interval is before ovulation, methods that anticipate ovulation by several days (such as the assessment of cervical mucus) would be particularly useful for couples who want to time their intercourse either to avoid or facilitate conception.