I chose not to get it while pregnant, despite a lot if 'encouragement' from HCPs, after weighing up the data myself and deciding that I wasn't happy with the risks. I'm in the fortunate position of being a scientist and so had access and the skill set to do that. In my particular case the jag was unlikely to work as I'd never had a primary course or the disease - the product info itself (for Repevax as was used at the time) states that it is a booster and so unlikely to give sufficient protection in immunologically naive patients.
Also at the time there was no evidence that it either would work, or be safe. Despite what some HCPs had been trained to say, the U.S. had only used a similar vaccine in pregnancy for 11 months longer than us, and so were still conducting trials themselves. There was no direct data on it's use in pregnancy. The advice was issued on weighing up data from other vaccines and animal studies etc, an approach that can have a wide margin of error. There has since been a study published using UK women as the trial group that did show some antibody response after vaccine that is expected to give a few weeks protection to a new born, and that short term risks were no higher with the vaccine (so risks like miscarriage, still birth etc). There is still no data on longer term risks, such as to neurological development or immune system development, because 4 years isn't that long in epidemiological terms.
Thirdly, I was worried by early data suggesting a blunting effect, whereby maternal antibodies reduce the effectiveness of the baby's own vaccines, even at levels that won't offer protection. This has since been confirmed, and while the JCVI considers that protecting newborns outweighs a possible increase in WC risk after the first few weeks I wasn't convinced.
Lastly, I looked at actual WC incidence in my area and it was clear it had returned to pre-peak levels, so the risk was no higher (in my case) than before the vaccine came out.
I chose to have it immediately after birth to try and give whatever minimal protection I could via breast milk. We wanted to cocoon as the Australians do, but were told that the vaccine was rationed and we couldn't even get it privately. Ds had his own vaccines on time, and it all worked out.