This rise can at least partly be attributed to the increasing popularity of fertility drugs and procedures such as IVF, which result in multiple births more frequently than unassisted fertilizations do. It may also be linked to the increase of growth hormones in food. Ethnicity
About 1 in 90 human births (1.1%) results from a twin pregnancy. The rate of dizygotic twinning varies greatly among ethnic groups, ranging as high as about 45 per 1000 births (4.5%) for the Yoruba to 10% for Linha São Pedro, a tiny Brazilian settlement which belongs to the city of Cândido Godói. In Cândido Godói, one in five pregnancies has resulted in twins. The Argentine historian Jorge Camarasa has put forward the theory that experiments of the Nazi doctor Josef Mengele could be responsible for the high ratio of twins in the area. His theory was rejected by Brazilian scientists who had studied twins living in Linha São Pedro; they suggested genetic factors within that community as a more likely explanation. A high twinning rate has also been observed in other places of the world, including:

Igbo-Ora in Nigeria
Kodinhi, located in Kerala, India
Mohammadpur Umri, located in Uttar Pradesh, IndiaThe widespread use of fertility drugs causing hyperovulation (stimulated release of multiple eggs by the mother) has caused what some call an "epidemic of multiple births". In 2001, for the first time ever in the US, the twinning rate exceeded 3% of all births. Nevertheless, the rate of monozygotic twins remains at about 1 in 333 across the globe.
Roths spots, also known as Litten spots or the Litten sign, are non-specific red spots with white or pale centres, seen on the retina and although traditionally associated with infective endocarditis, can occur in a number of other conditions including hypertension, diabetes, collagen vascular disease, extreme hypoxia, leukemia and HIV.Red and white retinal spots were first observed in 1872 by Swiss physician Moritz Roth, and named "Roth spots" six years later by Moritz Litten. They are typically observed via fundoscopy (using an ophthalmoscope to view inside the eye) or slit lamp exam.The original retinal spots identified in 1872 were attributed to nerve-fibres that had burst. Present-day analysis shows that they can be composed of coagulated fibrin including platelets, focal ischaemia, inflammatory infiltrate, infectious organisms, or neoplastic cells. Cause
Roths spots occur in conditions that predispose to endothelial damage of retinal capillaries, that is when there is dysfunction and disruption of the endothelium of retinal capillaries. Looking through the microscope reveals lesions with white centers made mainly of fibrin, depicting a fibrin-platelet plug at the site of vessel damage. Associated conditions
Conditions associated with Roths spots include:

Infective endocarditis
Anaemia/thrombocytopenia
Collagen vascular disease
Leukemia
Hypertensive retinopathy
Diabetic retinopathy
Pre-eclampsia
Human Immunodeficiency Virus (HIV)
Extreme hypoxia
Shaken-baby syndromeand also:
Candida albicans infection
vascular diseases
kala azar

Prevalence
Roths spots occur in only 5% of people with infective endocarditis. Litten, however reported a figure of 80%. See also
Oslers nodes
Janeway lesion
Splinter haemorrhage

References
External links
Image from the New England Journal of Medicine: Endocarditis
Image from the New England Journal of Medicine: CML