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  2. Age and female fertility - Wikipedia

    en.wikipedia.org/wiki/Age_and_female_fertility

    The average age of a girl's first period is 12 to 13 (12.5 years in the United States, [6] 12.72 in Canada, [7] 12.9 in the UK [8]) but, in postmenarchal girls, about 80% of the cycles are anovulatory in the first year after menarche, which declines to 50% in the third year, and to 10% by the sixth. [9]

  3. Birth spacing - Wikipedia

    en.wikipedia.org/wiki/Birth_spacing

    Birth spacing, pregnancy spacing, inter-birth interval (IBI) or inter-pregnancy interval refers to how soon after a prior pregnancy a woman becomes pregnant or gives birth again. There are health risks associated both with pregnancies placed closely together and those placed far apart, but the majority of health risks are associated with births ...

  4. Fertility - Wikipedia

    en.wikipedia.org/wiki/Fertility

    The average age of menarche in the United States is about 12.5 years. [34] In postmenarchal girls, about 80% of the cycles are anovulatory (ovulation does not actually take place) in the first year after menarche, 50% in the third and 10% in the sixth year. [35] Menopause occurs during a woman's midlife between ages 48 and 55.

  5. Is it a boy or girl? 24 old wives' tales about predicting a ...

    www.aol.com/news/boy-girl-24-old-wives-214126391...

    The only REAL ways to find out are scientific methods, like ultrasound (which can have a margin of error, especially if a boy is “shy” in the photos), amniocentesis, or non-invasive genetic ...

  6. Paternal age effect - Wikipedia

    en.wikipedia.org/wiki/Paternal_age_effect

    [32] A 2009 study examined children at 8 months, 4 years and 7 years and found that higher paternal age was associated with poorer scores in almost all neurocognitive tests used but that higher maternal age was associated with better scores on the same tests; [33] this was a reverse effect to that observed in the 2005 review, which found that ...

  7. Superfecundation - Wikipedia

    en.wikipedia.org/wiki/Superfecundation

    Ovulation is normally suspended during pregnancy to prevent further ova becoming fertilized and to help increase the chances of a full-term pregnancy. However, if an ovum is atypically released after the female was already impregnated when previously ovulating, a chance of a second pregnancy occurs, albeit at a different stage of development.

  8. Sex selection - Wikipedia

    en.wikipedia.org/wiki/Sex_selection

    China's 'one child family' policy is considered largely responsible for the substantial imbalance of the sex ratio. [53] Chinese government reports show that the sex ratio for newborns is 118:100 (boys: girls), higher in rural areas such as Guangdong and Hainan (130:100) compared to the average of 104:100 in developed countries. It is believed ...

  9. Advanced maternal age - Wikipedia

    en.wikipedia.org/wiki/Advanced_maternal_age

    In the US, the average age at which women bore their first child advanced from 21.4 years old in 1970 [11] to 26.9 in 2018. [4]The German Federal Institute for Population Research claimed in 2015 the percentage for women with an age of at least 35 giving birth to a child was 25.9%.