Women have been warned for every additional 100mg of caffeine a day – around half a cup of coffee – during the first trimester, birth weight can be lowered by up 2.5 ounces.

A new study from the University College Dublin says even women who drink less than the “safe” cut-off amount of two mugs of instant coffee (or three cups of tea) a day are more at risk of having low-birth weight or ­premature newborns.

The reason­ researchers give is the caffeine as it restricts blood flow to the placenta, slowing a baby’s growth, reports The Mirror.

In the study, Dr Ling-Wei Chen looked at 941 Irish mothers and babies where tea was the mothers’ main source of caffeine (48%), followed by coffee (38%).

The results suggest that for every additional 100mg of caffeine a day – around half a cup of coffee – during the first trimester, the baby tended to have a 2.5oz lower birth weight.

This amount of caffeine also decreased the babies’ length and head circumference, as well as their ­gestational age, which measures the length of pregnancy.

The women who consumed the most caffeine had babies weighing around 0.37lb (170g) less than those who had the least.

Even women who drank less than the “safe” amount of caffeine saw ­significant effects.

Dr Chen said: “Based on the consistent associations we observed we would recommend women who are pregnant or seeking to become pregnant at least limit their intakes of caffeinated coffee and tea.

“High caffeine intake can result in restricted blood flow in the placenta which may subsequently affect foetal growth. Caffeine can also cross the placenta readily, and because caffeine clearance slows as pregnancy progresses, caffeine accumulation may occur in foetal tissues.”

The researchers are concerned that people don’t know how much caffeine is in their cuppa.

Tea has less caffeine than a cup of coffee, but the exact amount depends on the brew time, water temperature and type of tea. So a cup of black tea contains anywhere between 23mg and 110mg of caffeine.

Share your comments below

  • It has caffeine so common sense tells you to limit its intake. I was pretty sick at the start of my pregnancies, so not much of anything passed my lips successfully


  • Another thing pregnant women can’t have,,, boo


  • I would have naturally assumed drinks containing caffeine wouldn’t be good during pregnancy. But I didn’t realise the affects could be this drastic


  • Wow, did not know this. I think to so,e degree it’s safer for the mother to stick to her usual routine


  • Reading that it restricts blood flow to the placenta worries me. Not due to believe it or not but speaking from experience, it didn’t affect my kids birth weight they were over average


  • Not only that Tea and Coffee deplete iron from your blood, as does some dairy products.
    Not pregnant, I had very low iron levels and ended up in hospital after fainting. My levels were less than 1/2 normal lower limit. 3 bags of blood. then 2 iron infusions via Outpatients a week apart.


  • Not so sure about this study! Kind of skeptical here.


  • Not too sure about this study….
    I drank a lot of coffee with my second pregnancy and he was the biggest


  • I dont believe that figure is correct that half a cup of coffee has ~100mg.
    100mg is more like 1 strong cup of coffee.


  • Interesting that they’re targeting tea. So many other drinks out there with higher caffeine content and in all honesty I’m over this scare mongering of pregnant women. Let their GP make these kinds of recommendations.


  • Not sure about this one. I was too sick to drink coffee with the first too but did with the third and she was the biggest.


  • I drank tea and I had really big babies. Everyone is different.


  • I don’t drink coffee. I used to drink some tea while pregnant (now just herbal teas) but no more than twice a day.


  • I didn’t have much coffee throughout my pregnancy, a tea now and then.


  • I’m glad I’ve had my children. Being pregnant these days is so stressful with all there studies telling you what you shouldn’t have !


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