Epidemiology of twin births from a climatic point of view.

Kamimura, Katsura

doi:10.1136/jech.30.3.175

Cited by 19 publications

(17 citation statements)

References 15 publications

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“…Elwood 6 noted that di zygoti c tw i nni ng rates i n Canadi an ci ti es (1952) show ed a seasonal vari ati on w i th an October maxi mum. Kami mura 7 reported for Japan that the bi rth rate of tw i ns rose to a maxi mum i n the l ate autumn or earl y w i nter, and Imai zumi et al 8 reported for Japan a hi gh preval ence of concepti ons of tw i ns i n April. James 9 identified a winter peak in triplet materni ti es that w as about 5% hi gher i n December than i n June i n Engl and and Wal es (1952-59 and 1963-75).…”

Section: Introductionmentioning

confidence: 99%

Seasonal variation of livebirths, stillbirths, extramarital births and twin maternities in Switzerland

Eriksson¹,

Fellman

2000

twin res

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A study was made of the seasonal variation in all births, and births according to marital status, multiplicity and birth status (live and still) in Switzerland recorded between 1876 and 1990. To obtain seasonal variation in as pure as possible form, our analyses are based on rates. When comparing the seasonality in data sets showing markedly different levels, standardised indices were used. Assuming the length of pregnancies with twins to be about one month shorter than for pregnancies with singletons, lagged twinning rates were calculated but, in comparison with actual twinning rates, the general seasonal variation remained. Therefore, this study was based on actual twinning rates. A monotonic increase in the amplitude of the seasonal variation in general births was noted for the period 1876-1930, with strong seasonal variation holding for 1921-1980. After that, a marked decline in the amplitude can be observed. Seasonality of both all births and twin maternities showed very similar pattern for the periods 1876-1930 and 1969-1990, with maxima in the spring (March-May) and troughs in late autumn (October-December). Twin maternities showed a strong seasonality for the period 1876-1930, being about 20% higher in March than in October. The twinning rate in the period 1876-1930 was about 2.6 per thousand units higher than in the period 1969-90. For twin maternities there was also a stronger seasonal variation during the earlier period than during the later one. The pattern of the seasonal variation for extramarital births, showing a maximum in February (conceptions in May-June) and a minimum in August (conceptions in November-December) with a difference of no less than 24% was more marked than for the marital births. It seems likely that this seasonality of extra-marital maternities was due mainly to seasonal variation of coital rates and multiple ovulation in the early summer months coinciding with optima of light, temperature and food supply. A strong reduction in the rate of stillbirths (gestational age more than 29 weeks) was observed during the twentieth century. The stillbirth rate declined from about 40 per 1000 in the 1870s to fewer than 5 per 1000 in the 1980s. Irrespective of this strong decline in the stillbirth rate, the same seasonal rhythm was noticed throughout the period with high stillbirth rates among births around March and low rates during the summer and autumn.

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Section: Introductionmentioning

confidence: 99%

Seasonal variation of livebirths, stillbirths, extramarital births and twin maternities in Switzerland

Eriksson¹,

Fellman

2000

twin res

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“…Seasonality of twinning has been reported from several countries [2][3][4][5][7][8][9][10][11]17]. However, the seasons when the excess of twinning was detected were not consistent among these reports which analysed the seasonality of overall twin births collectively for several years.…”

Section: Introductionmentioning

confidence: 99%

Alternate Changes in Birth Seasonality of Twins During 1971–1984 in Japan

Nakamura

Amau²,

Nonaka

et al. 1987

Acta genet. med. gemellol.: twin res.

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Birth dates of 1,536 twin-pairs in 1971-1984 were collected from the members of an association of twins' mothers. The seasonal variation of twinning changed every 2-4 years. Years when twinning rate was higher in the summer-fall season (1971-72, 1976-77, 1982-84) and those when a peak of the rate was not observed (1973-75, 1978-81) appeared alternately. In years with a summer-fall peak, the elevation of twinning in the summer-fall season was detected consistently in both like- and unlike-sexed and in both MZ and DZ twin groups. The twinning seasonality in these years, however, was not evident in twin births of mothers who were born in May-July. These results suggest the possibility that seasonal factors which influence the twinning rate be not multiple-ovulation-inducing but probably abortion-inducing factors and most likely seasonally epidemic microbes.

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“…The similar trend has also been observed in the present study where differences in the seasonality of twin birth is seen between the periods 1984-89 and 1990-93. lnfact this seasonality may vary from year to year depending upon ever changing determinants. This attribute may explain the inconsistencies seen in various reports (James, 1976;Kamimura, 1976;Sharma, 1980Sharma, , 1995Richter et al, 1984;Nakamura et al 1987) as far as the seasons showing excess of twinning. Because all the countries may not share factors that cause seasonality of twin births.…”

Section: Seasonality Of Twinningmentioning

confidence: 72%

“…The other reported factors affecting twinning rates include geographic, marital status, social class and biology (Rushton, 1987). Secular and seasonal variations in ~wi~ning rates are also often reported (James, 1972(James, , 1976Kamimura, 1976;Brackenridge, 1977;Nielsen et al, 1978;Parisi and Caperna, 1981;lmaizumi, 1987).…”

Section: Introductionmentioning

confidence: 92%

The epidemiological characteristics of twinning in Northwest India

Sharma

1997

Int. J. Anthropol.

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Jammu, the average twinning rate over the period 1984-93 were 10.70 and 11.40 respectively. Stillbirth rate among twins was much higher in Gujjars as compared to other three samples. Regional trends of twinning rate showed the highest incidence in the state of Uttar Pradesh, while the lowest in Tamilnadu. There were no significant differences between states for MZ twinning rate, while differences in the DZ twinning rate were significant in some instances. Maternal age and parity specific twinning rate showed the highest incidence at parity 4 and in the maternal age group 30-34 years. There was evidence of both seasonality and secular trends in twin births. The highest incidence of twin births over the period 1984-93 was noted in the summer season followed by rainy season, while the lowest in autumn. The average incidence of twinning in the Jammu region decreased from 13.76 during the years 1984-89 to 9.07 during the year 1990-93.

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Epidemiology of twin births from a climatic point of view.

Cited by 19 publications

References 15 publications

Seasonal variation of livebirths, stillbirths, extramarital births and twin maternities in Switzerland

Seasonal variation of livebirths, stillbirths, extramarital births and twin maternities in Switzerland

Alternate Changes in Birth Seasonality of Twins During 1971–1984 in Japan

The epidemiological characteristics of twinning in Northwest India

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