Prolonged pregnancy: evaluating gestation‐specific risks of fetal and infant mortality

Abstract

Objective To evaluate gestation‐specific risks of stillbirth, neonatal and post‐neonatal mortality. Design Retrospective analysis of 171,527 notified births (1989–1991) and subsequent infant survival at one year, from community child health records. Setting Notifications from maternity units in the North East Thames Region, London. Main outcome measures The incidence of births, stillbirths, neonatal and post‐neonatal deaths at each gestation after 28 completed weeks. Mortality rates per 1000 total or live births and per 1000 ongoing pregnancies at each gestation were calculated. Results The rates of stillbirth at term (2.3 per 1000 total births) and post‐term (1.9 per 1000 total births) were similar. When calculated per 1000 ongoing pregnancies, the rate of stillbirth increased six‐fold from 0.35 per 1000 ongoing pregnancies at 37 weeks to 2.12 per 1000 ongoing pregnancies at 43 weeks of gestation. Neonatal and post‐neonatal mortality rates fell significantly with advancing gestation, from 15 1.4 and 31.7 per 1000 live births at 28 weeks, to reach a nadir at 41 weeks of gestation (0.7 and 1.3 per 1000 live births, respectively), increasing thereafter in prolonged gestation to 1.6 and 2.1 per 1000 live births at 43 weeks of gestation. When calculated per 1000 ongoing pregnancies, the overall risk of pregnancy loss (stillbirth + infant mortality) increased eight‐fold from 0.7 per 1000 ongoing pregnancies at 37 weeks to 5.8 per 1000 ongoing pregnancies at 43 weeks of gestation. Conclusion The risks of prolonged gestation on pregnancy are better reflected by calculating fetal and infant losses per 1000 ongoing pregnancies. There is a significant increase in the risk of stillbirth, neonatal and post‐neonatal mortality in prolonged pregnancy. This study provides accurate data on gestation‐specific risks of pregnancy loss, enabling pregnant women and their carers to judge the appropriateness of obstetric intervention.

Maternal complications of pregnancy increase beyond 40 weeks of gestation in low-risk women

“…1 The post-term pregnancy, which occurs among <5% of gravidas 2 has been associated with an increased perinatal mortality rate. [3][4][5] Perinatal morbidity has also been noted to be higher in post-term pregnancies including meconium-stained amniotic fluid and meconium aspiration syndrome, 6 oligohydramnios, 7 macrosomia, 8,9 fetal birth injury, 10 rates of fetal distress in labor, 11 and rates of cesarean delivery. 5,12 While it is well established that these risks are increased in post-term pregnancy, what has received less attention is whether and to what extent these risks increase before 42 weeks' gestation.…”

Efficacy and safety of serial membrane sweeping to prevent post term pregnancy: a randomised study

“…2 The reported incidence of post-term pregnancy ranges from 4-18% and is associated with increased perinatal morbidity and mortality. 3,4 The Hannah review, the most recent Cochrane review and RCOG (Royal College of Obstetrics and Gynaecology) guidelines (Evidence-based Clinical Guidelines number 9) recommend that induction of labour should be offered at 41 weeks. 5,6 In our institution we practice elective induction of labour at or beyond 41 weeks in women with low risk pregnancies using cervical ripening agents whenever needed.…”

Review of Cesarean Section on Maternal Request in a Tertiary Care Institute; Scenario in Developing Country

“…It is further postulated that one death in 1500 neonates >1.5 kg in labour, one case of hypoxic ischemic encephalopathy in 1750 births and 10% of cases of cerebral palsy would be avoided by a policy of elective caesarean section. 33,34 These estimates are based on the risks of adverse fetal outcomes associated with labour. This argument for elective caesarean section is flawed by virtue of the fact that it disregards the possibility of iatrogenic fetal damage and makes the assumption that abdominal delivery will circumvent all the risks associated labour.…”