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Pregnancy Bliss | Reproductive Health Hub

Does "gas and air" have any adverse effect on the baby?

What are the injectable painkillers used in labour?
Pethidine is the most common injectable analgesic (painkiller) used. Debate still rages on the effectiveness of this drug in controlling pain. There is no question that pethidine has a strong sedative effect and there is quite a large section of the obstetrics and midwifery fraternity who believe that pethidine actually works through sedation rather than true pain relief.

A lot of women in labour have reported finding pethidine totally inadequate. The most common side-effect of pethidine is nausea and vomiting. In many units, an anti­-emetic (anti-sickness) drug to counter this is routinely administered with pethidine. Other units have a policy of administering an anti­-emetic only if the labouring woman complains of nausea and/or vomiting.
Pethidine can be given repeatedly every three hours or so, depending on requirements.

Are there any other injectable pain control drugs?
Yes. Diamorphine is another popular choice. The drawback is that this very powerful narcotic cannot be given repeatedly. This is because the problem of dependency sets in rather rapidly. In most units, it will be administered as a one-off at the onset of painful contractions or at any time in labour when the mother is in marked distress because of the pain.

Another positive aspect of diamorphine is the fact that it causes less nausea and/or vomiting when compared to pethidine.

Other injectables that have been used in labour but are less common include Meptazinol (Meptid®) and Pentazocine. They are both morphine-related opiates. They have no particular advantage over Pethidine.     

Are there any particular concerns about the use of pethidine and other similar injectable drugs in labour?
The main concern is its effect on respiration. While the depression of respiration on the labouring woman is so mild that it is of little or no concern, the effect on the fetus is a different story. Since these drugs cross the placenta to affect the fetus as well, the newborn may have such marked respiratory depression that he or she may require special help.

The respiratory depressive effect becomes an issue after birth and not before. However, the general sedative effect on the fetus may have such an effect on the heartbeat to the extent of forcing intervention of some kind. In fact, in most cases, that intervention is later found to have been unnecessary.

Is there any way of reversing the respiratory depressive effect of these drugs on the baby?
Yes. A narcotic antagonist drug called Naloxone can be injected to reverse the unwanted effects of diamorphine and other related drugs on the baby. This works quite quickly and is safe. However, while it is extremely effective in countering the effects of diamorphine, it is only partially effective in the case of Pethidine, Meptazinol or Pentazodne. Rarely, with these drugs, additional respiratory support may be required for the first few hours to allow the baby's body to completely rid itself of the drug.
Naloxone is also known by the name Narcan and various other trade names.

Are there circumstances where the use of these injectable painkillers may be undesirable?
On the same note as the unwanted effect on respiration, it may be less than ideal to use these drugs in a labour where a premature baby is going to be delivered. This is because the immature organs do not process the drug as efficiently and the effect will be marked and longer-lasting on these fragile beings.

Gas and Air (Entonox) is popular and safe but when it comes to the crunch, probably not that effective for most women

TENS machine 'Gas and Air' Oral medication Injectables Epidural