Fertility

Countries by fertility rate as of 2020
Chance of fertilization by menstrual cycle day relative to ovulation.
United States crude birth rate (births per 1000 population); Baby Boom years in red.

Capability to produce offspring through reproduction following the onset of sexual maturity.

- Fertility

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Sperm

Male reproductive cell, or gamete, in anisogamous forms of sexual reproduction .

Diagram of a human sperm cell
Sperm and egg fusing (fertilisation)
Dimensions of the human sperm head measured from a 39 year-old healthy human subject
Human sperm stained for semen quality testing
Motile sperm cells of algae and seedless plants

Thus, in humans, it is a measure of fertility in a man.

Semen analysis

A semen analysis (plural: semen analyses), also called seminogram or spermiogram, evaluates certain characteristics of a male's semen and the sperm contained therein.

Human sperm stained for semen quality testing in the clinical laboratory
Approximate pregnancy rate varies with amount of sperm used in an artificial insemination cycle. Values are for intrauterine insemination, with sperm number in total sperm count, which may be approximately twice the total motile sperm count.

It is done to help evaluate male fertility, whether for those seeking pregnancy or verifying the success of vasectomy.

Vagina

Elastic, muscular part of the female genital tract.

Diagram of the female human reproductive tract and ovaries
Pelvic anatomy including organs of the female reproductive system
An illustration showing a cut-away portion of the vagina and upper female genital tract (only one ovary and fallopian tube shown). Circular folds (also called rugae) of vaginal mucosa can be seen.
Medium-power magnification micrograph of a H&E stained slide showing a portion of a vaginal wall. Stratified squamous epithelium and underling connective tissue can be seen. The deeper muscular layers are not shown. The black line points to a fold in the mucosa.
Folds of mucosa (or vaginal rugae) are shown in the front third of a vagina.
A disposable plastic bi-valved vaginal speculum used in gynecological examination
A normal cervix of an adult as seen through the vagina (per vaginam or PV) using a bivalved vaginal speculum. The blades of the speculum are above and below and stretched vaginal walls are seen on the left and right.
Pre-menopausal vaginal mucosa (left) versus menopausal vaginal mucosa (right)
An ultrasound showing the urinary bladder (1), uterus (2), and vagina (3)
The womb represents a powerful symbol as the yoni in Hinduism. Pictured is a stone yoni found in Cát Tiên sanctuary, Lam Dong, Vietnam.
A sheep gives birth by vagina.

Before and during ovulation, the mucus glands within the cervix secrete different variations of mucus, which provides an alkaline, fertile environment in the vaginal canal that is favorable to the survival of sperm.

Down syndrome

Genetic disorder caused by the presence of all or part of a third copy of chromosome 21.

Illustration of the facial features of Down syndrome
A boy with Down syndrome using a cordless drill to assemble a book case
An eight-year-old boy with Down syndrome
Feet of a boy with Down syndrome, showing the deviated first toes
Brushfield spots, visible in the irises of a baby with Down syndrome
Karyotype for trisomy Down syndrome: notice the three copies of chromosome 21
Deaths due to Down syndrome per million persons in 2012
The risk of having a Down syndrome pregnancy in relation to a mother's age
Levitas and Reid have suggested that this early Netherlandish painting, The Adoration of the Christ Child, depicts a person with Down syndrome as one of the angels.
Father with son who has Down syndrome
Ultrasound of fetus with Down syndrome showing a large bladder
Enlarged NT and absent nasal bone in a fetus at 11 weeks with Down syndrome

Males with Down syndrome usually do not father children, while females have lower rates of fertility relative to those who are unaffected.

Sex position

Position of the body that people use for sexual intercourse or other sexual activities.

Various sex positons
A love scene sculpture from the Sunga period (c. 1st century BCE)
Tondo of an Attic red-figure kylix by the Triptolemos Painter, c. 470 BC, Tarquinia National Museum
A rear-penetration position, commonly referred to as 'doggy style'. The receiving partner can be penetrated either vaginally or anally.
The 'cowgirl' position
A couple performing sexual intercourse from a seated position, called the lotus position or lotus flower
One partner stands while holding up the other without a support, called the Suspended Congress in the Kama Sutra
Anal sex between two men in the missionary position
The T-square position
Modern drawing of fellatio
19th-century depiction of cunnilingus (detail) by Paul Avril
The 69 position
Woman performing anilingus on another woman
Drawing by Franz von Bayros showing an act of fingering
Double penetration
Two men and two women ringed in a circular foursome sex position performing four combinations of oral sex: M–F, F–F, F–M, M–M
A tergo in lying position

Pregnancy is a potential result of any form of sexual activity where sperm comes in contact with the vagina; this is typically during vaginal sex, but pregnancy can result from anal sex, digital sex (fingering), oral sex, or by another body part, if sperm is transferred from one area to the vagina between a fertile female and a fertile male.

Fertility medication

Hypothalamic–pituitary–gonadal axis in females, with estrogen exerting mainly negative feedback on FSH secretion from the pituitary gland.

Fertility medications, also known as fertility drugs, are medications which enhance reproductive fertility.

Age and female fertility

Cumulative percentage and average age for women reaching subfertility, sterility, irregular menstruation and menopause.
"Percentage of ovarian reserve related to increasing age. The curve describes the percentage of ovarian reserve remaining at ages from birth to 55 years, based on the ADC model. 100% is taken to be the maximum ovarian reserve, occurring at 18–22 weeks post-conception. The percentages apply to all women whose ovarian reserve declines in line with a particular model where late and early menopause are associated with high and low peak NGF populations, respectively. It is estimated that for 95% of women by the age of 30 years only 12% of their maximum pre-birth NGF population is present and by the age of 40 years only 3% remains. At birth, women have all their follicles for folliculogenesis, and they steadily decline until menopause."

Female fertility is affected by age and is a major fertility factor for women.

Semen quality

Countries by fertility rate as of 2020

Semen quality is a measure of male fertility, a measure of the ability of sperm in semen to accomplish fertilization.

Income and fertility

Graph of Total Fertility Rate vs. GDP (PPP) per capita of the corresponding country, 2015.
Demographic transition
TFR vs HDI showing "J curve", from UN Human Development Report 2009

Income and fertility is the association between monetary gain on one hand, and the tendency to produce offspring on the other.

Fertility and intelligence

The relationship between fertility and intelligence has been investigated in many demographic studies.

Map of countries by fertility rate (2020), according to the Population Reference Bureau

There is evidence that, on a population level, intelligence is negatively correlated with fertility rate and positively correlated with survival rate of offspring.