Newsgroup: it.scienza.medicina
Titolo: Pillola e gravidanze gemellari

Salve, vorrei sapere se è vero che quando dopo molti anni di utilizzo si
smette di prendere la pillola anticoncenzionale aumentano significativamente
le possibilità di gravidanze gemellari.
Grazie
-- 
Ciao mine

 significativamente le possibilità di gravidanze gemellari.
Aumenta sicuramente la probabilita' di un concepimento (infatti e' uno dei
metodi consigliati a chi desidera avere un figlio ma non riesce: prendere la
pillola per un certo periodo prima)...
Sulle gravidanze gemellari pero' non ho trovato nulla di concreto: su siti
"vari" si dice che puo' succedere, ma su quelli "blindati" non c'e' niente
di specifico (se non correlato a terapie per aumentare la fertilita', ma
quello e' noto).
Ciaotutti,
*

Avendo preso la pillola da poco, mi sono incuriosita e ho fatto una ricerca
veloce sulle medline. Ma, non essendo un medico, non č che ci abbia capito
molto ;-)
Hum Reprod. 1998 Jan;13(1):95-8.
Comment in:
Hum Reprod. 1998 Aug;13(8):2335-6.
Dizygotic twinning as a measure of human fertility.
Tong S, Short RV.
Department of Physiology, Monash University, Melbourne, Australia.
There is widespread concern about a possible decline in human fertility in
recent decades. The spontaneous dizygotic twinning rate provides a way of
measuring a combination of male plus female fertility as it reflects the
frequency of double ovulation, the probability of fertilization, and the
survival of the zygote. There was a decline in dizygotic twinning rates in
developed countries which began around 1960 and continued until the late
1970s. The exact cause of the fall remains unknown. We suggest that it could
have been due to a depression in the twin ovulation rate in women who
stopped taking the oral contraceptive pill. The rise in the dizygotic
twinning rates which occurred from the 1980s onwards in developed countries
is almost certainly due to increasing use of ovulation-inducing agents, but
this rise may have masked a continuing decline in dizygotic twinning.
Monozygotic twinning rates have remained remarkably constant or increased
only very slightly in recent decades. This makes it possible to use the
dizygotic:monozygotic twinning ratio to monitor dizygotic twinning in
populations where true incidence rates cannot be calculated, e.g. in
hospitals where there may be selective referral of twins.
Publication Types: Review
J Epidemiol Community Health. 1989 Sep;43(3):275-9. Related Articles, Links
Is there an increased risk of twinning after discontinuation of the oral
contraceptive pill?
Murphy MF, Campbell MJ, Bone M.
Department of Community Medicine and General Practice, Radcliffe Infirmary,
Oxford.
We investigated whether conception soon after cessation of use of oral
contraceptives affects the chance of bearing twins. Unpublished data from a
large sample survey of contraceptive practice in Scotland were used to
derive oral contraceptive discontinuation rates by month over the decade
1972-82 and these were related to estimated monozygotic and dizygotic twin
birth rates and proportions by month in Scotland from 1974-82, using
regression techniques. The results provide some support for the hypothesis
that there is an increased risk of conceiving monozygotic twins within a
year of ceasing to use oral contraceptives.
PMID: 2607308 [PubMed - indexed for MEDLINE]


Ovvero: ovulazione piu' regolare (niente gemelli dizigoti, quindi niente
doppia ovulazione), ma *potrebbe* esserci un aumento nella possibilita' di
concepire gemelli identici.
E' possibile che, statisticamente, i due effetti si annullino a vicenda (un
pollo a testa).
Comunque bisognerebbe anche vedere la formulazione delle pillole prese in
esame... 20 anni sono un'eternita' per la scienza moderna.
Ciaotutti,
*