Drugs (medicines) and their effects in Pregnancy
How common is the use of prescription and nonprescription drugs during pregnancy?
Fairly common. In the UK, three to four out of every ten pregnant women take some kind of medicine at least once during their pregnancies. This does not include iron or folic acid. In the USA, the figure is considerably higher.
What sort of medicines do women take commonly during pregnancy?
Mostly are the simple painkillers, paracetamol (Panadol®) being the leader. Also commonly taken are antibiotics and antacids taken to relieve heartburn. Common brands of antacids used in UK include Maalox®, Rennie®, Peptac® and Gaviscon®
Non-prescription medicines are taken far less nowadays, compared to twenty or thirty years ago.
The main concern of many, if not all, pregnant women, is the transfer of the drug across the placenta to the fetus. What is the general rule?
It is important to know that most drugs are transferred across the placenta to the fetus. The main issues are the rate of transfer, which differs from drug to drug, and the effect the drug is likely to have on the fetus. These will be discussed in due course.
What proportion of birth defects can be blamed on medicine taken during pregnancy?
The figure is not known for sure. However, in the Western world,, where approximate figures are available, it is estimated that about one in forty (2.5 per cent) of babies born with defects end up that way because of medicines takes by the mother during pregnancy.
This is about one in 1500 of all newborns, since babies with birth defects account for 2-3 per cent of all newborns.
Is there a particular period in pregnancy which can be described as especially sensitive?
Yes. The embryonic phase of pregnancy, which stretches up to the eighth week, is particularly sensitive to any foreign chemicals. This is the time when organs are being formed. Any damage occurring at this stage is irreversible.
A word of caution: Not all types of medication will cause damage to the fetus, even if taken in this sensitive period. Moreover, some medications taken outside this period could still inflict harm.
What are the antibiotics considered to be safe at any stage of pregnancy?
Penicillin is known by several different names and is known to be safe. Common penicillin drugs include amoxycillin, cloxacillin and methicillin. There are many other types.
Another group of antibiotics which are not known to cause any harm to the fetus are the cephalosporins. These too are known in a variety of names. Those commonly used include cephradine, cefuroxime, cefotaxime, cefalexin, cefaclor, and cefadroxil.
What about tetracyclines?
These are known to be harmful in the second half of pregnancy, where they can be incorporated in the developing bones and the forming teeth. With the latter, the discoloration caused is permanent.
Even though the confirmed harm appears to be confined to the second half of pregnancy, the standard advice is to avoid them throughout pregnancy. The advice also applies to the period after delivery, if the mother is breast-feeding.
What about trimethoprim?
This drug, which is commonly prescribed for urinary tract infection, is frowned upon by most doctors when it comes to use in pregnancy. There is a theoretical risk, yet to be confirmed, that the baby may be harmed. This is based on the fact that it is a folic acid antagonist. Most doctors would prefer to use alternatives.
What about septrin (Co-trimoxazole)?
Septrin is a well known old antibacterial drug. Its actual name is Co-trimoxazole. It is actually a combination of two drugs, one of which is trimethoprim. Because of the concern mentioned above for trimethoprim, the advice for septrin is the same: Avoid.