7








Pregnancy outcomes

 
     
 

KEY FINDINGS

  • The prevalence of major congenital anomalies was 41.8 per 1000 births.
  • There was a three-fold increase in anomalies of the circulatory system and neural tube defects.
  • Perinatal mortality was nearly four times higher in babies born to women with diabetes than in the general maternity population.
  • There was no evidence of a difference in the perinatal mortality of babies born to women with type 1 or type 2 diabetes.
 
 
 

7.1

 

Introduction

A principal aim of the data collection was to provide national perinatal mortality rates for babies of women with pre-gestational diabetes and details on congenital anomalies in babies born to these women. This chapter provides these rates, together with a description of the pregnancy outcomes.

 
 

7.2

 

Outcomes

Of the 3808 pregnancies notified to this study, 3742 (98.3%) resulted in a singleton birth. There were 64 sets of twins and two sets of triplets, equating to a multiple maternity rate of 1.7%, which is similar to the multiple maternity rate of 1.5% seen in the general maternity population of England and Wales.1

Of the 3808 pregnancies, there were 326 pregnancies delivering prior to 24 weeks. These comprised 64 legal abortions, 40 of which had an antenatally diagnosed congenital malformation; 261 in utero losses and two early neonatal deaths of a set of twins born at 20 weeks of gestation, both babies dying within an hour of birth. It is likely that there is an under-ascertainment of the actual number of pregnancies that ended before 24 weeks, as these women may not have accessed maternity services during the early stages of pregnancy.

The 3474 pregnancies (3414 singleton, 60 multiple) continuing at 24 weeks of gestation resulted in 87 stillbirths and 3449 live births.

 
 

7.3

 

Congenital anomalies

Suspected congenital anomalies in all live births, losses after 20 weeks and termination of pregnancy at any gestation were reviewed, as detailed in the methods section (Chapter 1). A total of 3591 offspring comprised 3451 live births, 87 stillbirths, 39 losses between 20 and 23 completed weeks of gestation and 15 terminations of pregnancy with a documented congenital anomaly. We compared observed confirmed congenital anomaly numbers with expected figures calculated using the EUROCAT 2002 maternal age-specific data.2

A total of 197 major congenital anomalies was identified and confirmed in 148 offspring giving a prevalence of confirmed major anomalies of 41.8 per 1000 total births (live and still). This compares with 21 per 1000 births from the EUROCAT data for 2002/03.3 The most common confirmed anomalies were congenital heart disease and those of the limb, musculoskeletal and connective tissue (Table 7.1).

The number of offspring with one or more major anomalies was 35 (23.3% of offspring with anomalies). These were frequently multiple anomalies of the heart or limb, musculoskeletal and connective tissue.

 
 

7.4

 

Perinatal mortality rates

Mortality rates were calculated using 2536 births occurring in 1 calendar year (deliveries between 1 March 2002 to 28 February 2003), allowing comparisons with other national perinatal mortality rates. This, therefore, excludes those women booking before, but delivering after, February 2003 (see Chapter 1 for detailed methodology). We compared perinatal mortality rates with national mortality data from the CEMACH 2002 perinatal death notification database and the Office for National Statistics.

The neonatal and perinatal mortality rates include a set of twins born at 20 weeks of gestation who both died within 1 hour of birth. Crude mortality rates show no significant differences in the perinatal mortality rates in babies born to women with type 1 diabetes and type 2 diabetes (P = 0.936) (Table 7.2).

Maternal age-adjusted mortality rates showed significantly higher stillbirth, perinatal and neonatal mortality rates within this pregnancy cohort when compared to the population of England, Wales and Northern Ireland in 2002; 4.7, 3.8 and 2.6 times higher, respectively (Table 7.3).

 
 

7.5

 

Discussion

 
 

7.5.1

 

Congenital anomalies

There was a greater than expected number of anomalies reported in this pregnancy cohort. This is primarily due to a higher number of neural tube defects (3.4 times expected numbers) and congenital heart disease (3.3 times expected numbers).

The prevalence of anomalies reported in this study is substantially less than that reported by other UK-based studies, 94 per 1000 and 83 per 1000 births.4,5 This is most likely due to differences in inclusion criteria with this study including only major anomalies as per EUROCAT classifications. Other European studies which have considered only major anomalies showed a similar rate to this study, 50 per 1000 and 42 per 1000 births.6,7

This study collected information on anomalies diagnosed up until day 28 of life. Defects identified after the neonatal period cannot therefore be enumerated. This means that the reported numbers of anomalies is likely to be an underestimate of the true number of anomalies seen in the offspring of these women.

Babies born to mother with diabetes are likely to be observed more closely following birth as they are at a high risk of other neonatal morbidities, such as respiratory distress and hypoglycaemia, than babies born to mothers without diabetes.8 It is therefore possible that some of the observed increase over expected numbers of cases of congenital heart disease is due to increased ascertainment in this group of babies following closer monitoring. However, this is unlikely to explain all of the increase and further work is required to understand the aetiology of these congenital anomalies with relation to diabetes.

Given the high numbers of neural tube defects seen in the offspring of these women it would appear necessary to specifically target these women with information concerning the benefit of folic acid supplementation prior to and during the first trimester of pregnancy.

 
 

7.5.2

 

Perinatal mortality rates

The stillbirth, neonatal and perinatal mortality rates reported for babies of this group of women are substantially higher than that observed in the general population with the stillbirth rate showing the greatest difference. Details on the causes of death of these babies were not available from this study but will be explored in the enquiry module of the CEMACH diabetes programme.

The national mortality rates in the offspring of women with type 1 diabetes presented here confirm previous regional studies conducted in the UK, which showed a stillbirth rate of 25.0 per 1000 and a perinatal mortality rate of 27.8 per 1000 live births and stillbirths.4,9 A recent population-based study in the Netherlands showed a perinatal mortality rate of 28 per 1000 live births and stillbirths in the type 1 diabetic population.10

Previous studies have reported perinatal mortality in the offspring of women with type 2 diabetes to be equivalent or higher than that seen to women with type 1 diabetes.11,12 There was no evidence from this study of a difference in the mortality rates of babies born to women with type 1 and type 2 diabetes. It is therefore important that services be targeted both to women with type 1 and with type 2 diabetes.

 
 

7.6

 

Conclusions

Prevalence of congenital anomalies and perinatal mortality rates remain high in the offspring of women with type 1 and type 2 diabetes. There is no evidence of a difference in perinatal mortality rates in the babies of women with type 2 diabetes when compared with women with type 1 diabetes. Further work is required to elucidate how women with diabetes, regardless of type, can be best enabled to improve the outcomes of their pregnancy.

 
     

References

  1. Office for National Statistics. Birth Statistics: Review of the Registrar General on births and patterns of family building England and Wales, 2002. Series FM1 No. 31. London: HMSO; 2004 [www.statistics.gov.uk/statbase/Product.asp?vlnk=5768].
  2. European Surveillance of Congenital Anomalies (EUROCAT). 2005. Personal communication.
  3. European Surveillance of Congenital Anomalies. EUROCAT Report 8: Surveillance of Congenital Anomalies in Europe 1980–1999. Newtownabbey: University of Ulster; 2002 [www.eurocat.ulster.ac.uk/pubdata/tables.html].
  4. Casson IF, Clarke CA, Howard CV, McKendrick O, Pennycook S, Pharoah PO, et al. Outcomes of pregnancy in insulin dependent diabetic women: results of a five year population cohort study. BMJ 1997;315:275–8.
  5. Hawthorne G, Robson S, Ryall EA, Sen D, Roberts SH, Ward Platt MP. Prospective population based survey of outcome of pregnancy in diabetic women: results of the Northern Diabetic Pregnancy Audit, 1994. BMJ 1997;315:279–81.
  6. Jensen DM, Damm P, Moelsted-Pedersen L, Ovesen P, Westergaard JG, Moeller M, Beck-Nielsen H. Outcomes in type 1 diabetic pregnancies: a nationwide, population-based study. Diabetes Care 2004;27:2819–23.
  7. Suhonen L, Hiilesmaa V, Teramo K. Glycaemic control during early pregnancy and fetal malformations in women with type I diabetes mellitus. Diabetologia 2000;43:79–82.
  8. Rennie JM, Roberton NRC. Textbook of Neonatology. 4th ed. Edinburgh: Churchill Livingstone; 2005.
  9. Penney GC, Mair G, Pearson DW, Scottish Diabetes in Pregnancy Group. Outcomes of pregnancy in women with type 1 diabetes in Scotland: a national population-based study. BJOG 2003;110:315–18.
  10. Evers IM, de Valk HW, Visser GHA. Risk of complications of pregnancy in women with type 1 diabetes: nationwide prospective study in the Netherlands. BMJ 2004;328:915–18.
  11. Clausen TD, Mathiesen E, Ekbom P, Hellmuth E, Mandrup-Poulsen T, Damm P. Poor pregnancy outcome in women with type 2 diabetes. Diabetes Care 2005;28:323–8.
  12. Cundy T, Gamble G, Townend K, Henley PG, MacPherson P, Roberts AB. Perinatal mortality in type 2 diabetes mellitus. Diabet Med 2000;17:33–9.