Noc for going abroad

Iam a defence civilian employee. Have 3yrs service. I was on el since may to aug 2016 for visiting my husband who is staying abroad. I have a dependent visa of 3yrs. My leave ended in aug . however as iam carrying right now i would like to extend my leave and stay with my husband till delivery. That would be in feb 2017. So i requested for loss of pay from aug 2016 on medical ground and i submitted a Sick note from UK which states that i am "not fit for work due to pregnancy related sickness". However now they are saying that NOC for going abroad can be given only for 180days and it cannot be extended. But there are so many people who stay abroad for 2yrs taking eol. I dnt plan to stay for 2yrs. But i would like to stay with my husband atleast till my delivery. They are saying maximum of 180days will be completed by nov hence i have to go back and join by nov Kindly request your help sir. Is there no option at all to extend noc from aug 2016 to may 2017. Getting a medical certificate here is very very difficult