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Delaying childbearing : Effect of age on fecundity and outcome of pregnancy

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Author: Noord-Zaadstra, B.M. van · Looman, C.W.N. · Alsbach, H. · Habbema, J.D.F. · Velde, E.R. te · Karbaat, J.
Type:article
Date:1991
Institution: Nederlands Instituut voor Praeventieve Gezondheidszorg TNO
Source:British Medical Journal, 6789, 302, 1361-1365
Identifier: 231385
Keywords: Health · Age · Conception · Fertility · Newborn · Pregnancy · Age Factors · Artificial Insemination · Cohort Analysis · Demographic Factors · Developed Countries · Europe · Fecundity--changes · Fertility · Fertility Measurements · Models, Theoretical · Netherlands · Population · Population Characteristics · Population Dynamics · Pregnancy · Pregnancy Outcomes · Pregnancy Rate · Probability · Reproduction · Reproductive Technologies · Research Methodology · Statistical Studies · Studies · Western Europe · Adult · Aging · Cohort Studies · Female · Fertility · Human · Infant, Newborn · Insemination, Artificial, Heterologous · Maternal Age · Menstrual Cycle · Models, Biological · Pregnancy · Pregnancy Outcome · Probability

Abstract

Objectives - To study the age of the start of the fall (critical age) in fecundity; the probability of a pregnancy leading to a healthy baby taking into account the age of the woman; and, combining these results, to determine the age dependent probability of getting a healthy baby. Design - Cohort study of all women who had entered a donor insemination programme. Setting - Two fertility clinics serving a large part of The Netherlands. Subjects - Of 1637 women attending for artificial insemination 751 fulfilled the selection criteria, being married to an azoospermic husband and nulliparous and never having received donor insemination before. Main ontcome measures - The number of cycles before pregnancy (a positive pregnancy test result) or stopping treatment; and result of the pregnancy (successful outcome). Results - Of the 751 women, 555 became pregnant and 461 had healthy babies. The fall in fecundity was estimated to start at around 31 years (critical age); after 12 cycles the probability of pregnancy in a woman aged >31 was 0.54 compared with 0.74 in a woman aged 20-31. After 24 cycles this difference had decreased (probability of conception 0.75 in women >31 and 0.85 in women 20-31). The probability of having a healthy baby also decreased - by 3.5% a year after the age of 30. Combining both these age effects, the chance of a woman aged 35 having a healthy baby was about half that of a woman aged 25. Conclusion - After the age of 31 the probability of conception falls rapidly, but this can be partly compensated for by continuing insemination for more cycles. In addition, the probability of an adverse pregnancy outcome starts to increase at about the same age. This study examined the age of the start of the fall (critical age) in fecundity, the probability of a pregnancy leading to a healthy baby taking into account the age of the women, and, by combining all of the results, the determination of the age-dependent probability of getting a healthy baby. 2 fertility clinics serving a large part of the Netherlands provided the 751 women who fulfilled the selection criteria. In this cohort study of all women who entered a donor insemination program, those who fulfilled the selection criteria were married to azoospermic husbands, were nulliparous, and never received donor insemination previously. Main outcome measures studied were the number of cycles prior to a pregnancy (positive pregnancy result) or the cessation of treatment and the result of the pregnancy (successful outcome). Of 751 women, 555 became pregnant and 461 had healthy babies. The drop in fecundity was estimated to begin at around age 31 (critical age); after 12 cycles, the probability of pregnancy in a woman age 31 was 0.54 compared with 0.74 in a woman age 20-31. After 24 cycles, this difference had decreased (probability of conception 0.75 in women 31 and 0.85 in women age 20-31). The probability of having a healthy baby also decreased, by 3.5% a year after the age of 30. Combining both of these age effects, the chance of a woman age 35 having a healthy baby was about 1.2 that of a woman age 25. After the age of 31, the probability of conception falls rapidly; however, this can be compensated for partly by continuing insemination for more cycles. In addition, the probability of an adverse pregnancy outcome begins to increase at about the same age.