For people with inflammatory arthritis, psoriasis, or inflammatory bowel disease, biologic drugs can be miracle drugs. It is not too much to say that these drugs have revolutionized treatment of these diseases. One thing that most people with these diseases have in common is getting diagnosed just before or during their peak child bearing years. 
My son was diagnosed with a type of inflammatory arthritis that effects the spine and was started on a biologic. He and his wife are at the time in their lives when they would like to start having babies. So that brings up some important questions. How do biologic drugs effect conception? Does my son’s drug increase the risk of a problem with his wife’s pregnancy? 
For young women on biologics – and there are growing numbers of them – how safe are biologics during conception, pregnancy, and breastfeeding? 
If you have watched any TV, you have probably heard an advertisement for a biologic drug. Common brand names are Humira and Enbrel. These drugs started being used in 1999. By 2012 there were nine, and new biologics are still being approved. 
Biologics are genetically engineered proteins. They are made from living organisms like a virus, a gene, or another protein. They are engineered to act like proteins that are a natural part of your body’s immune system. One of the most common types blocks a protein that is important in the process of inflammation called tumor necrosis factor. These drugs are called TNF inhibitors. Humira and Enbrel are TNF inhibitors. 
What We Know So Far
There have been lots of studies on the safety of biologics, but no controlled studies in pregnant women. Pregnant women are not allowed in these studies. Most women are advised to stop taking biologics several months before they try to get pregnant. 
But there is a growing number of women who have continued to take their biologic. Maybe because the alternative was felt to be worse than stopping it. Most other medications used for these conditions are known to be unsafe during pregnancy. In any case, we now have a growing number of case reports – many hundreds of cases – which we can start to gather data from. What we know so far is encouraging:
- There is no evidence that biologic use in men affects their fertility or causes any problems with their partners’ pregnancies. There is no evidence of an increased risk for birth defects or other problems in their children.
- Collected evidence from hundreds of pregnant women exposed to biologics during conception or the first trimester of pregnancy does not suggest any increased risk for adverse events during pregnancy or adverse outcomes in babies.
- In cases of women who have continued to breast feed while taking biologics, there have been no increased risk of adverse effects in babies.
But there are also reasons to remain cautious. These are still new drugs. We don’t have any large controlled studies proving their safety (and we are unlikely to get them). Also, most of the case reports are from older TNF inhibitor biologics. We have next to nothing on the newest biologics to come on the market. 
Another reason to be cautious is that all biologics may increase the risk of serious infection because they suppress the immune system. Studies show that biologics taken during the second and third trimester do cross through the placenta to the baby. These babies have been found to have lower white blood cell counts at birth. 
What to Do?
Men who are on a biologic should talk to their doctors about going off the biologic if they and their partners are thinking about conception. This may be overly cautious, but it is certainly an option if the risk of going off the medication is not too great. 
The current recommendation for women who want to conceive is to stop their biologic for several months before trying to get pregnant. Biologics are not recommended during pregnancy. 
Because a biologic taken during the later stages of pregnancy may lower a babies white blood cell count, babies born to mothers taking these drugs should not get any live vaccines (polio or chickenpox) for up to 6 months after birth. 
Although there is no evidence that breastfeeding is dangerous for babies of moms on a biologic, there is evidence that some of the biologic does get into breast milk.
Biologics are breakthrough drugs and are being taken by many young adults. So far, there is no evidence that these drugs pose an increased risk for pregnancy or breastfeeding. But as drug safety goes, we are still in early days. And, as with any drug use during pregnancy, absence of harm is not the same as proven safety. If your doctor recommends a biologic, talk about a plan for the possibility of pregnancy. 
- Medscape, Biologic Therapies and Pregnancy: The Story So Far.
- Arthritis Foundation, Biologics.