The problem with headlines on stress in pregnancy or small age gaps between babies, etc, is that they do not in any way report anything remotely accurate or helpful - they certainly don't helpfully summarise the real findings of the research in question. They merely report "increased risks" that are in reality tiny increases in risk within the general population as a result of what could actually be down to a whole host of sub-triggers within the potential trigger investigated as part of the research, therefore getting us no closer to any really helpful, concrete answers that can justifiably affect behaviour (or make an interesting journalistic article). For example, stress in pregnancy has an effect on the hormones circulating in the body, which may have a direct effect on foetal development and which genes get switched on or off, but also lowers the immune system, making you more vulnerable to viruses and bacteria that may have an effect on the developing foetus. Stress may also have an effect on your diet, exercise, light exposure, digestive system, etc, etc, all of which may affect the developing foetus... And people more prone to suffering symptoms of stress and anxiety may have genetic differences that make them more vulnerable to having children with autistic spectrum disorders regardless of how stressed they are whilst actually pregnant. Then, of course, there is the fact that stress in pregnancy is actually thought to increase the risk of physical disabilities, including spina bifida, and possibly mental illnesses like schizophrenia, and adult height, intelligence, learning disabilities, etc, etc. There doesn't appear to be an awful lot it hasn't been connected to, in the negative sense. And commonsense for centuries has informed us in any event that extreme stress and anxiety does us no good, so I don't really see how far forward any of this research has got us all. None of it is focused enough to be very helpful, it is just looking for confirmation of existing suspicions, which usually yields a result because that is what is wanted and expected at the start of the research.
Unless someone finds ways to refine the research and finds enough people to do the research on to make it valid, it really does feel like stabbing in the dark to me, or looking for proof of rather obvious assumptions. Even more so with respect to the age gap between someone's children... The crass reporting of all this research merely serves to increase a mother's stress load and feelings of self-blame, which we've already all agreed is not going to do her or her children much good...