Diabetes is a major disease affecting a growing percentage of the population. As a consequence there are a growing number of pregnant women with diabetes. There are two types of diabetes which exist prior to pregnancy: type 1 diabetes occurs due to a lack of the pancreatic islet b cells, caused by autoimmune destruction and resulting in an absolute lack of insulin; type 2 diabetes occurs due to insulin resistance and/or b cell dysfunction and is likely to be the result of interactions between genetic, environmental and immunological factors including diet, physical activity and obesity (DoH 2002). Insulin is required to transfer glucose into cells, a lack of insulin or insulin resistance therefore results in an inability to control blood glucose. Gestational diabetes exists as its name implies only in pregnancy and occurs due to metabolic changes during pregnancy and a lowering of glucose tolerance, as blood glucose rises more insulin is produced. Some women develop glucose intolerance of variable severity, resulting in gestational diabetes or impaired glucose tolerance. Treatment ranges from diet modification to insulin administration.

Since the introduction of insulin as a treatment for diabetes, mortality and morbidity rates have improved; however, they remain significantly higher than those of the general population. Research carried out in the last decade has shown perinatal mortality rates amongst babies of diabetic women ranging from 18.9 to 48 per 1000 live and stillbirths (Casson 1997; Hawthorne 1997; Hawthorne 2002), as opposed to a rate of 7.9 per 1000 amongst the general population (CESDI 2001). Langer 2000 suggest that control of blood sugar level should be viewed as a continuum, different thresholds of glucose control being associated with different fetal complications. These complications include higher rates of miscarriage, stillbirth, congenital anomalies and macrosomia (possibly leading to birth injury). Recent rates of congenital anomalies in babies of women with diabetes have been reported as ranging between 83 and 94 per 1000 births as opposed to a rate of between 9.7 and 21.3 in the general population (Casson 1997; Hawthorne 1997). The optimum glycated haemoglobin level is generally agreed to be between 4 and 8 mmol/l (Williams 2003; Hawthorne 2002); however, even women with established diabetes, whether they are type 1 or 2 rarely achieve these levels (Maresh 2001).

A potential problem in the assessment of the management of diabetes has been suggested by Kilpatrick 1997, Kilpatrick 1998, John 1997 and Marshall 2000. They comment that differences have been found in the ranges and results produced by laboratories using the same methods of assessment to measure the same glycaemic index; thus a degree of caution should be used when interpreting multicentre studies using several labs to analyse specimens. Continuous glucose monitoring systems are beginning to be used selectively and provide a dynamic picture of interstitial glucose levels, converting these levels to an electrical signal, which produces an average recording of glucose level every five minutes. Studies using the continuous glucose monitoring system in conjunction with other methods of assessment such as glycated haemoglobin and intermittent glucose monitoring have found it useful in providing additional information in relation to hypo/hyperglycaemia, which is of particular importance during pregnancy (Buhling 2004; Hirsch 2005; Kerssen 2004; Porter 2004). The addition of continuous glucose monitoring should provide a more accurate picture of control over a 24 hour period and reduce the impact of anomalies associated with glycated haemoglobin monitoring.

There remains controversy regarding the degree to which blood glucose level should be controlled. A Cochrane review carried out by Walkinshaw (Walkinshaw 1999) concluded that twenty‐five years after first demonstrating an improvement in pregnancy outcome from controlled glycaemia in women with diabetes, it is still uncertain how tightly controlled diabetes needs to be in pregnancy in order to achieve the optimum outcome. It is generally agreed that those women who are normally managed with oral hypoglycaemics should, when pregnant, change to insulin treatment in order to achieve optimum control. An oral hypoglycaemic Cochrane protocol is currently being prepared.

There are several methods of administering insulin to women who require it in pregnancy. Conventionally, insulin has been administered subcutaneously in the form of a basal/bolus regimen, often referred to as multiple daily injections (MDI), this consists of pre‐meal boluses of short‐acting insulin and a later evening basal injection of long‐acting insulin, usually given with pen injection devices. The advantage of MDI is that blood sugar levels can be tightly controlled by frequent, self‐regulated adjustment of dose, necessary because of the dynamic insulin requirements of pregnancy (Hadden 1996). An alternative insulin administration method is the continuous subcutaneous insulin infusion pump (CSII). Modern pumps are small and lightweight, are battery operated and hold enough insulin for several days. Different basal rates can be preset and boluses given as required. Potentially CSII maintains the basal rate of insulin and reduces the risk of hypoglycaemia, decreases the risk of fasting hyperglycaemia (the dawn phenomenon) and improves patient compliance, as the woman does not have to constantly inject insulin (Gonzalez 2002). Hadden 1996, however, suggests that although insulin pumps offer the treatment effects of conventional regimens they may be too complex for routine use. Selective use of pumps for those who are motivated and with difficult to control diabetes is an alternative to widespread use.

There are three CSII pumps used in the UK, Disetronic H‐Tron, Disetronic D‐Tron and MiniMed 508. Despite widespread use of CSII pumps in other countries such as Germany, France, Italy and the USA, they are used infrequently in the UK; reasons for this are likely to be conservatism, cost concerns and reports of episodes of diabetic ketoacidosis (Colquitt 2004). Mecklenburg 1984, Knight 1985 and Brink 1986 found improved diabetic control with CSII as opposed to MDI. Mecklenburg 1984 and Knight 1985, however, found an increased incidence of ketoacidosis although Knight 1985 did not obtain his groups by randomisation and stated that generally ketoacidosis was precipitated by illness. Both studies found the incidence of ketoacidosis reduced with time, suggesting education was a factor. Brink 1986 found no increased incidence in diabetic ketoacidosis using CSII as opposed to MDI. A recent meta‐analysis of randomised controlled trials assessing glycaemic control with CSII as opposed to MDI did not identify an increased risk of ketoacidosis with the use of CSII (Pickup 2002). The authors suggest that this may be due to the short duration of the trials and poor reporting although improvements in pump technology are likely to have played a part.

Both short‐acting insulin (SAI) analogues and regular human insulin is given via CSII and MDI for the treatment of diabetes. It has been suggested by some authors that the use of SAI analogues reduces episodes of hypoglycaemia and improves metabolic control (Anderson 1997; Johansson 2000). This improved control is thought to be due to short‐acting insulin analogues ability to achieve peak plasma concentrations approximately twice as high and in approximately half the time of regular insulin (Siebenhofer 2004a). A recent Cochrane review of short‐acting insulin analogues verses regular human insulin in patients with diabetes mellitus (Siebenhofer 2004b), however, concluded that, and taking into account the low quality of trials included in the meta‐analysis, there appeared to be only a negligible benefit with SAI analogues over regular human insulin in the majority of patients with diabetes treated with insulin. The authors suggest caution in the use of SAI analogues and that more robust studies need to be carried out to produce more robust findings.

It is recognised that both continuous subcutaneous infusion and multiple daily injections offer the advantage of frequent dose adjustment, which should lead to optimum blood sugar level attainment. It is less clear, due to the lack of any systematic review of the evidence concerning the use of these different methods of administration during pregnancy, which method achieves the best outcome in terms of normalising blood sugar level and reducing hypo/hyperglycaemia in order to prevent associated complications for both mother and child.