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Pregnancy over age 50 has, over recent years, become more possible for women, due to recent advances in assisted reproductive technology, in particular egg donation. Typically, a woman's fecundity ends with menopause, which by definition is 12 consecutive months without having had any menstrual flow at all. During perimenopause, the menstrual cycle and the periods become irregular and eventually stop altogether, but even when periods are still regular, the egg quality of women in their forties is typically dramatically lower than in younger women, making the likelihood of conceiving a healthy baby also dramatically lower, particularly after age 42.〔Advanced Fertility Center of Chicago, Female Age, Fertility and Infertility ()〕 Men, in contrast, generally remain fertile throughout their lives,〔The Alfred Foundation. (n.d.) (Men's Health ). Retrieved May 18, 2007.〕 although the risk of genetic defects is greatly increased due to the paternal age effect. Other sources claim that men might experience a decline in fertility starting in their late 30s.〔http://www.mayoclinic.com/health/pregnancy/PR00115〕 In the United States, between 1997 and 1999, 539 births were reported among mothers over age 50 (four per 100,000 births), with 194 being over 55.〔Salihu, Hamisu M., Shumpert, M. Nicole, Slay, Martha, Kirby, Russell S., & Alexander, Greg R. (2003). (). ''Obstetrics & Gynecology, 102 (5),'' 1006-1014. Retrieved March 5, 2007.〕 Among 12,549 African and Middle Eastern immigrant mothers, confirmed by DNA testing, two were found to be older than fifty; the oldest mother being 52.1 years at conception (and the youngest mother 10.7 years old).〔Forster P, Hohoff C, Dunkelmann B, Schürenkamp M, Pfeiffer H, Neuhuber F, Brinkmann B. (2015) "Elevated germline mutation rate in teenage fathers". ''Proc Biol Sci'' 282:20142898 ()〕 According to statistics from the Human Fertilisation and Embryology Authority, in the UK more than 20 babies are born to women over age 50 per year through in-vitro fertilization with the use of donor oocytes (eggs).〔Hall, Sarah. (May 8, 2006). "(Surge in number of children in UK born to mothers over 50 )." ''The Guardian.'' Retrieved March 29, 2007.〕 Maria del Carmen Bousada de Lara is the oldest verified mother; she was aged 66 years 358 days when she gave birth to twins; she was 130 days older than Adriana Iliescu, who gave birth in 2005 to a baby girl. In both cases the children were conceived through IVF with donor eggs. The oldest verified mother to conceive naturally (listed currently in the Guinness Records) is Dawn Brooke (UK); she conceived a son at the age of 59 years in 1997 while taking estrogen. ==Medical considerations== The risk of pregnancy complications increases as the mother's age increases. Risks associated with childbearing over the age of 50 include an increased incidence of gestational diabetes, hypertension, delivery by caesarean section, miscarriage, preeclampsia, and placenta previa.〔〔Schienberg, Jonathan. (November 9, 2004). "(New Age mystic to become mom at 57 )." ''CNN.'' Retrieved March 4, 2007.〕 In comparison to mothers between 20 and 29 years of age, mothers over 50 are at almost three times the risk of low birth weight, premature birth, and extremely premature birth; their risk of extremely low birth weight, small size for gestational age, and fetal mortality was almost double.〔Lister Hill Center for Health Policy. (October 31, 2003). (Pregnancy After 50: More Risky Than We Thought? ) Retrieved Sept 11, 2014.〕 ==Cases of pregnancy over 50== Facts about the conception of pregnancies in this age group can be difficult to determine, but they are nearly always due to the use of IVF with donor eggs. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Pregnancy over age 50」の詳細全文を読む スポンサード リンク
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