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RCOG release: What you need to know about having a small baby

News 24 October 2014

Lifestyle factors can reduce some of the risks of having a small baby, advises new patient information published today by the Royal College of Obstetricians and Gynaecologists (RCOG).

An unborn baby is small if, at that stage of pregnancy, his or her size or estimated weight on the scan is in the lowest 10% of babies.

A baby’s weight is affected by several factors including; the mother’s weight and height, whether the mother or father were a small baby, ethnicity, number of pregnancies and the sex of the baby. A baby could be small because of a combination of these factors and is likely to be healthy, because he or she is meant to be small.

However, in certain cases babies are small because they are not growing properly, known as growth restriction. Having a growth restricted baby can increase the risk of stillbirth, neonatal mortality and morbidity.

Possible reasons for growth restriction include; the placenta not working effectively because of conditions such as pre-eclampsia, anaemia, infection or having a baby with a developmental or genetic condition.

Lifestyle factors such as smoking, drug use, over-exercising or not eating healthily are also linked to an increased risk of growth restriction. Other factors which may increase the risk of having a baby who is growth restricted are; a maternal age of 40 or above, high blood pressure, having kidney problems or diabetes complications.

The guidance emphasises the importance of leading a healthy lifestyle during pregnancy in order to help reduce the risk of having a growth restricted baby including; reducing or quitting smoking, eating healthily and avoiding recreational drug use can help reduce the risk.

A woman’s risk of having a small baby is assessed in early pregnancy by a midwife or obstetrician. If a woman is at an increased risk, extra monitoring will be offered to check the baby’s growth and wellbeing.

Cath Broderick, Chair of the RCOG Women’s Network said:

“If your baby is diagnosed as small, a multidisciplinary team will support you and offer close monitoring throughout your pregnancy and help ensure the best outcome for both mother and baby.

“It’s important to have reassurance and someone to answer your questions. If you have any concerns, please consult your midwife or obstetrician who will be able to help.”

Philippa Marsden, Chair of the RCOG’s Patient Information Committee, added:

“This information reinforces the message that healthcare professionals should encourage women to lead a healthy lifestyle at every intervention to reduce the possibility of any adverse pregnancy outcomes. The RCOG advocates a life-course approach for women, promoting prevention rather than intervention and placing the individual at the centre of their care throughout their life.”


For further information, please contact the RCOG Media and PR team on +44 20 7772 6300 or email


This information has been developed by the RCOG Patient Information Committee. It is based on the RCOG Green-top Guideline No. 31, The Investigation and Management of the Small-for-Gestational-Age Fetus (2013) and was aimed at reducing the incidence of stillbirth nationally by assessing a woman’s risk of having a small a baby in early pregnancy and a clear monitoring strategy if that is the case.