MIDIRS Essence > October 2008 > Informed Choice

Prolonged Pregnancy

Originally posted on Oct 2008

Following on from my article about the recent educational launch of the National Institute for Health and Clinical Excellence (NICE) Induction of labour guidelines (NICE 2008), I’d like to focus on MIDIRS Informed Choice title, Prolonged pregnancy.

This title recognises that where pregnancy is prolonged, if women are to be able to make an informed choice, they need to receive information about the possible risks to their own health and their baby’s. Women also need information about what approaches can be used to induce labour and the risks associated with these various methods, as well as the risks associated with continuing the pregnancy in the expectation that their labour will start spontaneously. Ultimately, however, the decision as to whether or not to be induced will depend on a woman’s individual interpretation of her risk, the personal and social implications of remaining pregnant, as well as the implications for the baby. The decision to induce labour can also have an impact on the workload of the midwifery and obstetric teams, and the care resources available.

The estimated due date (EDD) of a woman’s pregnancy has considerable social and emotional significance for the woman, her partner and their family, and provides a time frame in which to prepare for the birth of the baby. It also has significance for midwives, obstetricians and neonatologists who use the EDD to estimate key stages of fetal development and to assess fetal well-being. Traditionally, the time frame for the duration of human pregnancies has been calculated from the first day of the woman’s last menstrual period (Baskett & Nagele 2000) and is regarded as being around 280 days or 40 weeks (Cunningham et al 2005). Preterm birth is therefore defined as occurring before the 37th week of pregnancy and post-term beyond the 42nd week or 294 days. However, these calculations were first determined over 300 years ago and have been used ever since. It is only comparatively recently that the original calculations have been challenged for their accuracy alongside technological advances in the use of ultrasound to assess gestation (Baskett & Nagele 2000, Cunningham et al 2005). Such advances have led to NICE’s recommendation that women’s EDD should now be calculated by ultrasound (dating scans), performed early in the first trimester of pregnancy and no later than 16 weeks (NICE 2008). This has been shown to reduce the proportion of births considered post-term (Gardosi et al 1997), as well as the number of inductions undertaken for this reason (Tunón et al 1996).

The natural incidence of prolonged pregnancy is difficult to ascertain because of the range of clinical interventions present in modern obstetric practice (Roach & Rogers 1997). However, estimates about the frequency of prolonged pregnancy suggest that 89% of deliveries occur between 37 and 41 weeks, 4% are prolonged and the remaining 7% are preterm (Caughey et al 2005, Cleary-Goldman et al 2006, Richardson & Mmata 2007). Prolonged pregnancy has been associated with an increase in both maternal and neonatal morbidity and it is recognised that there is a small, but consistent rise in perinatal mortality in infants born beyond 42 weeks’ gestation. These outcomes are considered to be avoidable and have subsequently resulted in closer attention to the management of prolonged pregnancy using interventions designed to either stimulate labour onset or expedite the birth.

There are various approaches to labour induction, but in the main, these are perceived to involve medical interventions in the form of drugs or the clinical procedure of rupturing the membranes. However, labour induction has been associated with many approaches in the past – traditional remedies and ‘old wives’ tales, to the more recent use of alternative therapies in the form of herbs, homeopathy and acupuncture. Any of these approaches should be reviewed for their efficacy in terms of effectiveness as well as for their potential to do harm. Similarly, midwives need to be aware that some women may be conversant with these methods but they might be less informed about whether their use is appropriate and/or safe for them and their pregnancy.

The debate related to the choices between labour induction and expectant management for prolonged pregnancy continues and is considered in great detail within this title. The review of the published literature has demonstrated that there would still appear to be considerable controversy surrounding the management of prolonged pregnancy, based on uncertainty about the degree of fetal risk and disagreement over the need for medical intervention and the role of fetal assessment (Roach & Rogers 1997, RCOG 2001). Despite this controversy, the National Institute for Health and Clinical Excellence (NICE) currently recommend that all women should be offered induction of labour between 41 and 42 weeks’ gestation (NICE 2008).

The information contained in Prolonged pregnancy, offers both expectant women and their health care professionals access to the very latest research-based evidence to support informed decision making and best practice. Women need to be given accurate, up-to-date and unbiased information about the risks of prolonged pregnancy, the options for elective induction of labour or expectant management and increased surveillance and the potential benefits or risks of these. Having been given this information, they must be given ongoing support by their health care professionals, whatever their decision and whatever the outcome of their pregnancy.

MIDIRS review of this topic has highlighted the lack of robust evidence relating to the use of alternative approaches to labour initiation, women’s ability to access these, and the availability of appropriate support should women choose to use these methods. The most glaring omission from the available evidence though, is the lack of research into women’s feelings about, and experiences of, prolonged pregnancy. There is a need for new research which explores women’s lived experiences of both induced labour and expectant management of pregnancy beyond 41 weeks’ gestation alongside more exploration of the clinical and social context of giving women a defined date for the birth based on estimations. I hope that by reading Prolonged pregnancy, practitioners may feel inspired to undertake research in these areas and produce the evidence-base, whose application is so fundamental to best practice in modern, responsive maternity and neonatal care services.

References

Baskett TF, Nagele F (2000). Naegele’s rule: a reappraisal. BJOG 107(11):1433-5.

Caughey AB, Washington AE, Laros RK (2005). Neonatal complications of term pregnancy: rates by gestational age increase in a continuous, not threshold, fashion. Am J Obstet Gynecol 192(1):185-90.

Cleary-Goldman J, Bettes B, Robinson JN et al (2006). Postterm pregnancy: practice patterns of contemporary obstetricians and gynecologists. Am J Perinatol 23(1):15-20.

Cunningham FG, Leveno KJ, Bloom SL et al (2005). Williams obstetrics. 22nd ed. New York: McGraw-Hill.

Richardson A, Mmata C (2007). NHS maternity statistics, England: 2005-06. London: The Information Centre.

Gardosi J, Vanner T, Francis A (1997). Gestational age and induction of labour for prolonged pregnancy. Br J Obstet Gynaecol 104(7):792-7.

National Institute for Health and Clinical Excellence (2008). Induction of labour. London: NICE.

Roach VJ, Rogers MS (1997). Pregnancy outcome beyond 41 weeks gestation. Int J Gynecol Obstet 59(1):19-24.

Royal College of Obstetricians and Gynaecologists (2001). Induction of labour. London: RCOG Press [These guidelines are currently in the process of being updated – see NICE 2008 reference].

Tunón K, Eik-Nes SH, Grøttum P (1996). A comparison between ultrasound and a reliable last menstrual period as predictors of the day of delivery in 15 000 examinations. Ultrasound Obstet Gynecol 8(3):178-85.

Vicky Carne| Head of Midwifery| MIDIRS

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