Last updated: December 2012
The UK has the highest teenage pregnancy rate in Western Europe. 
• Figures for England and Wales in 2010 show 34,633 conceptions to women aged under 18, a decline of 9.5 percent from 2009 .
• In England and Wales, the estimated number of conceptions to girls aged under 16 was 6,674 in 2010, a decline of 6.8 percent from 2009 .
• Pregnant women younger than 18 years have an increased risk of preterm labour before 32 weeks of gestation, as well as maternal anaemia, and chest and urinary tract infections .
• Age plays a key role in the increased risk of preterm delivery, low birth weight and neonatal mortality, and one that is not dependent on socio-economic status .
• Teenage mothers are more likely to experience postnatal depression and difficulties with breastfeeding than older women .
• A 2001 study showed that non-smoking women aged 15–19 having a first birth were not at increased risk of adverse obstetric outcomes compared with women aged 20-29 .
• However, when having a second birth, the same non-smoking women aged 15–19 were at significantly increased risk of both premature delivery and stillbirth compared with women aged 20-29 .
1. UNICEF. A league table of teenage births in rich nations. Innocenti report card, issue No 3. Florence: The United Nations Children’s Fund, 2001. Also available at: www.unicef-irc.org/publications/pdf/repcard3e.pdf (accessed 25 November 2012).
2. Office for National Statistics. Conceptions in England and Wales 2010. Available at: www.ons.gov.uk/ons/dcp171778_258291.pdf (2010, accessed 25 November 2012).
3. Jolly MC, Sebire N, Harris J, et al. Obstetric risks of pregnancy in women less than 18 years old. Obstetrics and Gynecology 2000;96(6):962–6.
4. Chen XK, Wen SW, Fleming N, et al. Teenage pregnancy and adverse birth outcomes: a large population based retrospective cohort study. International Journal of Epidemiology 2007;36(2):368-73.
5. Horgan RP, Kenny LC. Management of teenage pregnancy. The Obstetrician & Gynaecologist 2007;9(3):153–8.
6. Smith GC, Pell JP. Teenage pregnancy and risk of adverse perinatal outcomes associated with first and second births: population based retrospective cohort study. BMJ 2001;323(7311):476.
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Smoking and pregnancy
• The 2010 Infant Feeding Survey reported that a quarter (26 percent) of mothers in the UK smoked at some point in the 12 months before or during their pregnancy. Of these, just over half (54 percent) gave up at some point before the birth. However, one in eight mothers (12 percent) smoked throughout their pregnancy .
• Smoking in pregnancy increases the risk of miscarriage, reduced birthweight and perinatal death. If parents continue to smoke after the pregnancy, the risk of sudden infant death syndrome also increases .
• The occurrence of low-birthweight babies could be reduced by an estimated 20 percent if all women were non-smokers during pregnancy. The impact of smoking on these outcomes can be reduced if women gave up smoking before their third trimester .
• Women who smoke during pregnancy double the risk of stillbirth. The rate of infant mortality is also nearly double. However, if the mother stops smoking in the first trimester, these risks are comparable with those for women who were non-smokers from the beginning of pregnancy .
1. Health and Social Care Information Centre. Infant feeding survey 2010: early results. Available at: www.ic.nhs.uk/webfiles/publications/003_Health_Lifestyles/IFS_2010_early_results/Infant_Feeding_Survey_2010_headline_report2.pdf (2010, accessed 25 November 2012).
2. Health and Social Care Information Centre. Statistics on smoking: England 2012. Available at: www.ic.nhs.uk/webfiles/publications/003_Health_Lifestyles/Statistics%20on%20Smoking%202012/stats_smok_eng_2102_rep.pdf (2012, accessed 25 November 2012).
3. US Department of Health & Human Services. The health consequences of smoking: a report of the Surgeon General. Chapter 5: Reproductive effects. Available at: www.surgeongeneral.gov/library/reports/smokingconsequences/index.html (2004, accessed on 25 November 2012).
4. Wisborg K, Kesmodel U, Henriksen TB, et al. Exposure to tobacco smoke in utero and the risk of stillbirth and death in the first year of life. American Journal of Epidemiology 2001;154(4):322–7.
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Diet and nutrition and pregnancy
• A 1995 World Health Organization study found that the range of maternal weight gain associated with optimal and healthy birthweight was 10–14 kg, with an average weight gain of 12 kg . This is only a rough guide and varies, for example, depending on a woman’s pre-pregnancy weight and body mass index (BMI).
• In practice, there is no one-size-fits-all approach to pregnancy weight gain. In the UK, there are no official recommendations and women of normal weight gain an average of 11–16 kg during pregnancy.
- Folic acid has a 72 percent protective effect against neural tube defects (e.g. spina bifida) . As a supplement, it should be taken before conception to ensure its effect is felt in the earliest stages of growth.
- Iron deficiency anaemia is common in pregnancy and severe iron deficiency anaemia is associated with low birthweight and prematurity .
- A healthy and balanced diet should be the goal in pregnancy, as at any other time of life. There is an increased demand for energy, protein and several micronutrients during pregnancy, including thiamine (vitamin B1), riboflavin (vitamin B2), folic acid, calcium and vitamins A, C and D .
- As a daily supplement, the World Health Organization recommends not exceeding 10,000 IU vitamin A (3000 micrograms RE) at any time during pregnancy .
- Foodborne illnesses can contribute to maternal and fetal disease, miscarriage and preterm birth. Risk can be minimised by eating fully cooked meat and eggs, avoiding unpasteurised cheese and rinsing fruits and vegetables prior to consumption .
- Pregnant teenagers need to ensure a good calcium intake as their own bones are still growing .
- Dieting to lose weight or fasting during pregnancy are not advised, and have been linked to higher levels of neural tube defects .
1. Anon. Maternal anthropometry and pregnancy outcomes. A WHO Collaborative Study. Bulletin of the World Health Organization 1995;73(Suppl):1–98.
2. Anon. Prevention of neural tube defects: results of the Medical Research Council Vitamin Study. MRC Vitamin Study Research Group. Lancet 1991;338(8760):131–7.
3. Fortner KB, Kuller JA, Brown HL. Nutrition in pregnancy. Feature article in The Female Patient. Available at: www.thewomenshealthcenter.com/wp-content/uploads/2012/07/Nutrition-in-Pregnancy.pdf (2009, accessed 25 November 2012).
4. Royal College of Obstetricians and Gynaecologists. Nutrition in pregnancy. Scientific Impact Paper No.18 (revised September 2010). Available at: www.rcog.org.uk/files/rcog-corp/uploaded-files/SIP_No_18.pdf (2010, accessed 25 November 2012).
5. World Health Organization. Micronutrient Initiative. Safe vitamin A dosage during pregnancy and lactation: recommendations and report of a consultation. Geneva: WHO; 1998. Available at: http://apps.who.int/iris/bitstream/10665/63838/1/WHO_NUT_98.4_eng.pdf (accessed 25 November 2012).
6. Williamson CS. Nutrition in pregnancy. Nutrition Bulletin 2006;31(1):28–59.
7. Carmichael SL, Shaw GM, Schaffer DM, et al. Dieting behaviors and risk of neural tube defects. American Journal of Epidemiology 2003;158(12):1127–31.
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Obesity and pregnancy
Explanation of body mass index (BMI)
BMI, as defined below by the World Health Organization , is a useful rough guide to obesity. The calculation used to obtain a person’s BMI is weight (in kilograms) divided by height (in metres) squared:
• Underweight: < 18.5
• Normal weight: 18.5–24.9
• Overweight: 25.0–29.9
• Obesity Class I: 30.0–34.9
• Obesity Class II (severe): 35.0–39.9
• Obesity Class III (morbid): ≥ 40.0
• 19 percent of women of child-bearing age are estimated to be obese (BMI ≥ 30) .
• In the UK, nearly 5 percent of women have a BMI ≥ 35 at some point in their pregnancy .
• Obese mothers are twice as likely to experience a stillbirth as mothers within the normal weight range . The higher the BMI, the greater the risk.
• Pregnant women with a BMI ≥ 35 are more likely to have a range of pre-existing conditions such as diabetes and hypertension. They are also more likely to develop these problems during pregnancy .
• The link between obesity and preterm birth in general is demonstrable. Overweight or obese mothers are more likely to have an early preterm birth (before 32 weeks), and are more likely to have an induced preterm birth overall (before 37 weeks) . This increased percentage for induced preterm birth rises with weight, from 15 percent for overweight women to 70 percent for those who are very obese . The mechanisms behind this trend are complex and not fully understood.
• Obesity and increasing BMI have also been associated with a 2–3 percent increased risk of induced labour, caesarean section, primary postpartum haemorrhage and large-for-their-gestational-age babies . Such infants are more liable to birth injuries, perinatal asphyxia and problems such as neonatal respiratory distress and metabolic instability .
• Recent research indicates that a BMI > 25 increases the chance of an early miscarriage, with a yet higher chance for higher BMIs .
1. World Health Organization Europe. A healthy lifestyle. Body mass index – BMI. Available at: www.euro.who.int/en/what-we-do/health-topics/disease-prevention/nutrition/a-healthy-lifestyle/body-mass-index-bmi (2012, accessed 25 November 2012).
2. Centre for Maternal and Child Enquiries. Maternal obesity in the UK: findings from a national project. London: CMACE, 2010. Also available from: www.publichealth.hscni.net/sites/default/files/Maternal%20Obesity%20in%20the%20UK.pdf (accessed 26 November 2012).
3. Chu SY, Kim SY, Lau J, et al. Maternal obesity and risk of stillbirth: a metaanalysis. American Journal of Obstetrics & Gynecology 2007;197(3):223–8.
4. McDonald SD, Han Z, Mulla S, et al. Overweight and obesity in mothers and risk of preterm birth and low birthweight infants: systematic review and meta-analyses. BMJ 2010;341:c3428.
5. Vasudevan C, Renfrew M, McGuire W. Fetal and perinatal consequences of maternal obesity. Archives of Disease in Childhood. Fetal and Neonatal Edition 2011;96(5):F378-82.
6. Metwally M, Ong KJ, Ledger WL, et al. Does high body mass index increase the risk of miscarriage after spontaneous and assisted conception? A meta-analysis of the evidence. Fertility and Sterility 2008;90(3):714–26.
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Mental health and pregnancy
The risks to child and mother from mental health problems are often secondary – due for instance to unhealthy maternal behaviours – and are hard to track statistically. The effects of the drugs used to treat mental disorders in pregnant mothers and unborn children are just beginning to be researched.
• Untreated depression can lead to harmful prenatal health behaviours, such as poor nutrition, poor prenatal medical care, smoking, alcohol or other substance misuse and risk of suicide .
• Large studies show that 10–16 percent of women fulfill the major depressive disorder diagnostic criteria. With the exception of paroxetine, the negative side effects associated with selective serotonin reuptake inhibitors (SSRIs), which are typically used as antidepressants, are, overall, considered to be outweighed by the dangers of leaving depression untreated .
• A 2012 study on SSRIs taken during pregnancy and the risk of persistent pulmonary hypertension in the newborn, carried out on a cohort from five Scandinavian countries, found the risk to be low, although use of SSRIs in late pregnancy increases that risk more than twofold .
• Studies into the side effects of SSRI use in pregnancy have looked at infant withdrawal from the drugs  and at the increased risk of preterm delivery , as evidence of a link for both has been observed.
Stress and anxiety
• Pregnant women with high stress and high anxiety levels are at increased risk of spontaneous abortion and preterm labour. There is also an increased incidence of malformation, reduced head circumference in particular. The long-term effects are not clear or well understood .
• Mothers with lifetime anxiety disorders are more likely to have children with similar disorders. Leaving aside behavioural or genetic factors, there is some evidence that distress during pregnancy increases the likelihood of this happening .
1. Pearlstein T. Perinatal depression: treatment options and dilemmas. Journal of Psychiatry and Neuroscience JPN 2008;33(4):302–18.
2. Soufia M, Aoun J, Gorsane MA, et al. [SSRIs and pregnancy: a review of the literature.] Encephale 2010;36(6):513–6.
3. Kieler H, Artama M, Engeland A, et al. Selective serotonin reuptake inhibitors during pregnancy and risk of persistent pulmonary hypertension in the newborn: population based cohort study from the five Nordic countries. BMJ 2012;344:d8012.
4. Sanz EJ, De-las-Cuevas C, Kiuru A, et al. Selective serotonin reuptake inhibitors in pregnant women and neonatal withdrawal syndrome: a database analysis. Lancet 2005;365(9458):482–7.
5. Lund N, Pedersen LH, Henriksen TB. Selective serotonin reuptake inhibitor exposure in utero and pregnancy outcomes. Archives of Paediatrics & Adolescent Medicine 2009;163(10):949–54.
6. Mulder EJ, Robles de Medina PG, Huizink AC, et al. Prenatal maternal stress: effects on pregnancy and the (unborn) child. Early Human Development 2002;70(1–2):3–14.
7. Martini J, Knappe S, Beesdo-Baum K, et al. Anxiety disorders before birth and self-perceived distress during pregnancy: associations with maternal depression and obstetric, neonatal and early childhood outcomes. Early Human Development 2010;86(5):305–10.
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Exercise and pregnancy
Exercise before and during pregnancy is beneficial over and above its mitigating effect on weight gain.
Regular exercise before pregnancy reduces the likelihood of developing gestational diabetes mellitus by as much as 55 percent. This figure remains as high as 25 percent for those exercising in the early stages of pregnancy .
• Recent research has shown that mothers doing regular exercise have a positive effect on their babies’ cardiovascular health. Their babies’ heart rates were lower and showed greater variability than those whose mothers were doing no exercise. The long-term effects have yet to be studied .
• Even a low-intensity, 16-week walking programme from week 20 of pregnancy has been shown to have significant benefits for blood pressure levels and cardiovascular health. The effect was particularly marked in overweight women .
1. Tobias DK, Zhang C, van Dam RM, et al. Physical activity before and during pregnancy and risk of gestational diabetes mellitus: a meta-analysis. Diabetes Care 2011;34(1):223–9.
2. May LE, Glaros A, Yeh HW, et al. Aerobic exercise during pregnancy influences fetal cardiac autonomic control of heart rate and heart rate variability. Early Human Development 2010;86(4):213–17.
3. Stutzman SS, Brown CA, Hains SM, et al. The effects of exercise conditioning in normal and overweight pregnant women on blood pressure and heart rate variability. Biological Research for Nursing 2010;12(2):137–48.
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Alcohol and pregnancy
• It is estimated that around 1 percent of pregnant women consume alcohol regularly .
• Alcohol consumption among pregnant women may well be underestimated because data on rates of alcohol consumption are commonly based on self-reporting , which is unreliable.
• The damage caused by alcohol on the developing fetus is dependent on the level and frequency of maternal alcohol consumption and the stage of pregnancy during which alcohol is consumed. Other factors to be taken into consideration include: maternal age; genetic makeup of mother and fetus; mother’s general health and nutritional status; socio-economic status and drug use (including tobacco use) .
• Alcohol consumption is also associated with infertility, miscarriage, low birthweight, preterm labour and stillbirths .
• Regular and heavy alcohol consumption affects the fetus in a number of ways. These are usually grouped together under the umbrella term fetal alcohol spectrum disorders (FASDs). FASDs include growth deficiency and central nervous system dysfunction, the latter leading to intellectual, developmental (e.g. heart defects) and learning disabilities [1, 2].
• Advice on ‘safe’ alcohol consumption can vary, though the UK Chief Medical Officer’s advice to women who are pregnant or trying to conceive is to avoid alcohol altogether. If a woman then chooses to drink, the advice is to drink no more than 1–2 units once or twice a week to minimise the risk to the baby .
1. The Royal College of Midwives. Alcohol and pregnancy. Guidance paper. Available at: www.rcm.org.uk/EasySiteWeb/getresource.axd?AssetID=112535 (2010, accessed 25 November 2012).
2. NHS Choices. Can I drink alcohol if I’m pregnant? Available at: www.nhs.uk/chq/Pages/2270.aspx?CategoryID=54&SubCategoryID=130#close (2012, accessed 25 November 2012).
In this section
Premature birth statistics