Duration of pregnancy

The duration of pregnancy is approximately 280 days this time period extends from the first day of the last menstrual period to birth. Pregnancy is divided into three periods of three calendar months each 3-month period is called a trimester. 

For treatment of acute thromboembolism, adjusted-dose low-molecular-weight heparin or unfractionated heparin should be used for the duration of pregnancy and for 6 weeks after delivery. Warfarin should be avoided after the first 6 weeks of gestation because it may cause fetal bleeding, malformations of the nose, stippled epiphyses, or CNS anomalies. 

As in the other studies, maternal toxicity, such as the animal s behavior, clinical symptoms, mortality and general physical condition, food consumption and body weight, is examined during the study. The duration of pregnancy, course of birth, and body... 

Since adverse health effects are of concern, particularly for prenatal exposure to PCBs, Lackmann et al. (1999) investigated the influence of maternal age and duration of pregnancy on serum concentrations of PCBs in full-term neonates. Blood samples were taken from 80 full-term German neonates within the first 12 hours of life, before the first oral feeding. The median serum concentration of total PCBs was... 

Oxytocin. The action of oxytocin on the uterus shows species variations and is influenced by sex hormones. The uterus isolated from rat or guinea-pig contracts in the presence of oxytocin. The sensitivity of the human uterus to oxytocin increases with the duration of pregnancy so that an intravenous injection of 1 mU/ min has the same action at the end of pregnancy as 16 mU/min at the beginning. The pregnant uterus shows rhythmic contractions, the rate of which depends upon the dose of the peptide. The non-pregnant human uterus shows almost no response to oxytocin, even in large doses. Paradoxically it is much more sensitive to vasopressin which causes the symptoms of dysmenorrhoea. 

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