The answer is probably although no studies have formally tested this and so Lantus insulin is not officially indicated for use in pregnancy. That being said many doctors do prescribe Lantus to pregnant woman needing insulin and so far there has been no issues reported to suggest any concern.
A reasonable approach is to continue to use Lantus insulin in woman with type 1 diabetes but to use approved insulins for women with gestational diabetes requiring insulin.
Levemir (Insuin detemir) is approved for use in pregnancy by the FDA and EMA and trials are ongoing looking at the safety for Tresiba (insulin degludec).