Regional variations in uterine blood flow in the guinea pig: relationship to pregnancy site distribution.

The alterations which occur in the total uterine blood flow (UBF) during early pregnancy in the guinea pig were determined using electromagnetic blood flow probes. Between days 4 and 6 postcoitum, UBF rose from basal levels of 1.2 ml/min to peak levels of 3.0 ml/min. The elevated levels corresponded temporally with the onset of blastocyst implantation. Between days 7 and 8, UBF declined to basal levels. In guinea pigs possessing three pregnancy sites per uterine horn on days 10-20, obvious regional differences in UBF were observed. Consistently higher UBF measurements were monitored from uterine segmental arteries supplying the tubal and cervical thirds of the uterus than from those distributed to the middle third of the uterus. These data indicate that regional variations in UBF exist in the guinea pig which may be involved in the regulation of pregnancy site selection or subsequent placental-fetal growth.