Pregnancy demands extreme care and precautionary measures in order to provide an adequate environment for the development of the baby. The use of mobile phones has always been a subject of discussion in the domain of development & technology. It is evident from research that though these devices do not exhibit any harm during the early stages of life yet after a prolonged use, these can cause some significant harms to your health. Mobile phones have been a recent revolution and hence it’s not possible to predict its disadvantages as well as ill-effects on human health in such a short notice.
Possible threat:
For developing baby, an ionizing radiation is more harmful as compared to a non-ionizing one. X-rays as well as radiations rendered by a CT scan can cause harms to the developing baby as ionizing radiation can bring about changes at metabolic level. Mobile phones render a milder version of non-ionizing radiation and therefore exhibit little or no impact in the first few years but can be hazardous over longer period of use.
Steps that should be taken in order to avoid the ill-effects of mobile phones on baby:

Less use:  You should make use of mobile phones as less as possible. You can send a message in form of text from your mobile as well as use alternatives like landline phones. These alternatives help you by providing you an aegis against the radiations emitted during the call. Use your phone as little as possible, and only when you have no alternative - send a text or use a landline instead
Short Calls: You should consider your mobile phones as utility devices that should be used only at moments of emergency. You should make all your long talks from your landline and till then you should avoid making any long call from your mobile.

Abandon if signals low: you should try to use your cell as less as possible when the signal is low. Under such a situation the level of emitted radiation increases significantly and therefore can harm you even more. You should try coming out of your house or near the window in order to make a call as this can aid you in receiving better signal strength.

Use hands-free set: though mobile phones do release some undesired radiations yet its intensity can be significantly reduced by using a headphone. In this manner you would significantly increase the distance between you as well as your mobile phone. This would significantly contribute in providing less pressure to your brain.
Analyze reviews: You should carefully analyze the reviews before buying any mobile phone as this can help you in reaching decisive conclusions about a handset. Though very rare, yet some models are often susceptible to self combustion. Such information can be easily collected from customer reviews.

Check SAR Rating: Always check the SAR rating before purchasing a mobile phone as this would inform you of the level of radiation in the electromagnetic spectrum.

Prohibit use during driving: Whether pregnant or not, you should discard the use of mobile phones during driving as it significantly reduces the responsiveness of mind and therefore there is an increased risk of accident.