The election of Abraham Lincoln in 1860 was the immediate cause of southern resolutions of secession. He was the nominee of the Republican party with an anti-slavery expansion platform, he refused to acknowledge the right to secession, and he would not yield federal property within Southern states.
The gestation period of a human, from time of conception to birth is approximately 9 months (266 days/38 Weeks). 9.5 months is calculated from the first day of the last menstrual period (280 days/40 Weeks).
Gestation period, the duration of pregnancy, in humans being about 266 days (38 weeks) from the time of fertilization until birth 3.  266 days is the average gestation period for humans from conception to birth 4. End of Week 38. (266 Days from Conception) - Estimated birth date. 5.