if talaq was given 3 times with time after every of them more than "3 periods", nearly more than 3 months, i.e. for example, 1st talaq, 4 months, remarry, 2nd talaq, 4 months, remarry, 3rd talaq, then a year (said in comment), and she did not marry other men between and after these, you cannot remarry her before she marries to another man.
if talaq was given 3 times with waiting time less than "3 periods" after them, for example, 1st talaq, 2 months, taking her back, 2nd talaq, 2 months, taking her back, 3rd talaq, a year - then only 1 full divorce is counted, and you can remarry her, without need for her to marry other man.
proof: https://islam.stackexchange.com/a/32792 .
pregnant woman can be divorced, and waiting term is "until they lay down their burden" , according to quran 65:4 : https://islamqa.info/en/12287 .