summary - Europe PMC

0 downloads 0 Views 577KB Size Report
fetal distress, oligohydramnios, fetal macrosomia, fetal dysmaturity, and perinatal mortality, as many as 80% of post-term fetuses appear completely normal.
1----

Stanislaw Iwanicki,

MD, FRCSC

Albert Akierman,

MB, BS, FRCPC

The Management of Post-Term Pregnancy

SUMMARY

RESUME

Although post-term pregnancy is associated with an increased incidence of fetal distress, oligohydramnios, fetal macrosomia, fetal dysmaturity, and perinatal mortality, as many as 80% of post-term fetuses appear completely normal. The authors of this article discuss the three sub-groups of post-term pregnancies, and deal with the diagnosis and antepartum and intrapartum management of the condition. Recommendations and a protocol for management are provided. (Can Fam Physician 1988; 34:2027-2029.) Key words: post-term pregnancy, diagnosis,

Bien que la grossesse passee terme soit associee a une incidence accrue de d6tresse foetale, d'oligohydramnios, de macrosomie foetale, de retard de croissance intrauterin et de mortalite p6rinatale, plus de 80% des foetus n6s apres terme semblent tout a fait normaux. Les auteurs de cet article discutent des trois sous-groupes de grossesses post-terme, abordent le diagnostic et la ligne de conduite ante-partum et intra-partum de cette condition. Ils pr6sentent aussi des recommandations et suggerent un protocole.

management

I__ l~

Drs. Iwanicki and Akierman are members of the Division of Neonatology, Department of Obstetrics and Gynecology,

University of Calgary Medical School, and staff members of Calgary General Hospital. Requests for reprints to: Dr. Stanislaw Iwanicki, 2319 Uxbridge Dr. N.W., Calgary, Alta., T2N 3Z7 T HE MANAGEMENT of posttermn uncomplicated pregnancy remains an obstetrical dilemma and has been the subject of hot debate. Continued intra-uterine existence beyond forty-two weeks gestation is associated with a high incidence of placental insufficiency, fetal post-maturity (dysmaturity), and increased risk of perinatal death. 1 The unfavourable outcome could theoretically be pre-empted by well-timed induction of labour and delivery of a healthy infant. However, a disconcerting feature of induction of CAN. FAM. PHYSICIAN Vol. 34: SEPTEMBER 1988

labour is that it may cause an increase in Caesarean section rates.2'3 Furthermore, selection of patients for induction of labour is hampered by uncertainty relating to gestational age. There is a distinct lack of prospective randomized studies clearly demonstrating advantages of induction of labour. At the same time, reliable protocols for conservative management of uncomplicated post-term pregnancy are lacking. Cole4 found no statistical difference in maternal or fetal outcome between a group ofpregnant women induced and delivered at 39-40 weeks gestation as compared with a group allowed to continue the pregnancy indefinitely. Gibb3 found no difference in fetal or neonatal outcome, but the Caesarean section rate rose to 27% . Large retrospective studies also failed to demonstrate advantages of induction of labour for postmaturity. Chalmers5 found that induction rates between 1965 and 1975, in Cardiff, U.K., rose from 7.5% to 26.5% without any

change in the perinatal mortality rate, although Caesarean section rates rose by over 50% and the forceps rate more than doubled. Induction of labour appears invariably to increase Caesarean section rate even if the most successful techniques of induction are used, including vaginal application of prostaglandin gel.6 However, the risk of having a Caesarean section when the cervix is favourable appears to be negligible. The purpose of induction of labour is to prevent undiagnosed fetal asphyxia and subsequent fetal death. Ultrasound examination can ascertain fetal growth and assess the fetal biophysical profile, particularly the volume of amniotic fluid.7 Careful clinical management, making use of ultrasound examination and fetal heart-rate monitoring, has been found to be sufficient to ensure optimal perinatal outcome in the postterm pregnancy without the need for routine induction of labour.8 A question that remains to be answered is 2027

which post-term pregnancies should be developed nipples and genitalia), as allowed to continue and which should well as appearances of intra-uterine be induced. malnutrition (lack of subcutaneous fat and dry peeling skin). The undernourished fetus may be at higher risk of Definitions and Incidence morbidity and mortality, including of Post-Term Pregnancy growth retardation, meconium aspiraPregnancy is considered post term tion syndrome, and some degree of when it exceeds 294 days (42 weeks) neurological sequelae. Larger postcalculated from the first day of the last term infants may be subjected to longer menstrual period. Average human ges- labour and more traumatic delivery, tation lasts 280 days (40 weeks). The and are less able to tolerate asphyxia chance of delivery on the calculated without long-term neurological sedue date is only 5 %.' The chance of de- quelae. livery within three days of the due date is 29%, while delivery within two weeks of the due date is 80%.' The Diagnosis of prevalence of post-term pregnancy Post-Term Pregnancy used to be assessed as 10%-12% of all Menstrual history was found to be pregnancies until the advent of dating unreliable in as many as 40% of pregpregnancies using ultrasound, which nancies, and for this reason it is frereduced this figure to less than 1.1 %. quently oflittle help in establishing a diOligohydramnios, common in post- agnosis of post-term pregnancy. 12 Ulterm pregnancy, is associated with a trasound has been accepted as a reliable statistically significant increase in fetal acidosis, meconium aspiration, and Table 1 low Apgar scores. Any single vertical Management Protocol pool ofamniotic fluid measuring over 3 Gestational Age cm on ultrasound examination is considered normal amniotic fluid volume. Before 20 weeks Inability to demonstrate this amount of 24 weeks amniotic fluid would be classified as oligohydramnios.7 32 weeks

Effect of Post-Term Pregnancy on the

At all antenatal visits

Post-term pregnancy is associated with an increased incidence of fetal distress, oligohydramnios, fetal macrosomia, fetal dysmaturity, and perinatal mortality. 10 However, as many as 80% of post-term fetuses appear completely normal. " It has been observed that prolonged pregnancy falls into three sub groups: * patients with incorrect dates; * patients with correct dates but in whom physiological maturity is not achieved until after 42 weeks gestation; and * patients with correct dates in whom maturity occurs at 40 weeks gestation but labour fails to ensue. The fetuses in the last group display features of postmaturity syndrome.'0 These infants show signs of advanced maturity (hard skull bones, narrow sutures, long fingernails, and well-

At term and post term

Fetus and Neonate

2028

41 weeks 42 weeks

After 42 weeks Intrapartum

Note:

method of assessing gestational age. When performed before 20 weeks gestation, it will help to predict gestational age within approximately seven days. The incidence of post-term pregnancy fell to 1.1 % in one study when the diagnosis was restricted to patients in whom both menstrual and ultrasound - determined dates exceeded 293 days.9 If proper documentation of gestational age is missing, the diagnosis of post-term pregnancy is difficult, if not impossible. The date of the last menstrual period and the measurement of fundal height are of limited value in determining gestational age. Routine use of ultrasound would therefore reduce the number of falsely diagnosed postterm pregnancies, and consequently would also reduce the risk of inappropriate intervention. Furthermore, if ultrasound examination is performed at 32 weeks gestation, about 80% of intrauterine growth retardation will be

U/S for dating. Start FM chart. U/S to exclude IUGR. Check AF volume by palpation. If oligohydramnios suspected, perform U/S. If oligohydramnios diagnosed, induce labour irrespective of cervical status. NST Induce labour if cervix is favourable. If cervix is unfavourable, commence biweekly NST alternating with BPP. Induce labour if NST or BPP is not reassuring or cervix becomes favourable. Direct fetal heart-rate monitoring with fetal scalp pH/gases if needed.

U/S - ultrasound examination; FM - fetal movements; AF - amniotic fluid; NST - non-stress test; BPP - biophysical profile; IUGR - intrauterine growth retardation.

CAN. FAM. PHYSICIAN Vol. 34: SEPTEMBER 1988

detected. These pregnancies should not present. If the cervix remains uncontinue beyond term. 13 favourable and induction of labour is deemed essential, application of prostaglandin gel vaginally may prove sucAntepartum and cessful in ripening the cervix. In addiIntrapartum Management tion, it may provide a contraction stress Assessment of post-term pregnancy test at the same time. If fetal well-being is difficult and may prove expensive. is compromised as demonstrated by Not all post-term pregnancies are accu- non-stress test, biophysical profile, rately dated or easily inducible. A prac- contraction stress test, or cordocentesis tical and inexpensive fetal monitoring with analysis of blood pH and gases, system is required. Fetal movement Caesarean section without attempted charts,'4 non-stress tests, contraction- induction is best elected, since virtually stress tests, ultrasounds with assess- all such fetuses will develop acute disment of amniotic fluid volume or tress with induction. An attempt to asbiophysical profile'5 have been used sess volume of amniotic fluid should be with variable success. Most authors made at every antenatal visit. agree that testing should start no later All post-term fetuses should have dithan 42 weeks gestation. Screening be- rect fetal heart-rate monitoring fore 40-42 weeks gestation would have throughout labour and delivery. If the to include almost 50% of all pregnant tracing is not reassuring, fetal scalp patients, and, therefore, should be re- blood pH and gases should be deterstricted to free or inexpensive tests such mined. as fetal movement charts or non-stress tests. If a pregnancy continues beyond 42 Conclusions and weeks gestation, most authors agree Recommendations On the basis of the above discussion, that timing of delivery should be based on cervical status. If the cervix is we would suggest that where possible, favourable and the dates are well docu- all pregnant women undergo two ultramented, the risk of failed induction is sound examinations: one, for dating, small. In such cases, induction will cir- before 20 weeks gestation, and the seccumvent the high costs of further test- ond at 32 weeks for detection of intrauterine growth retardation. All patients ing of fetal well-being. When the cervix is unfavourable at should observe and record fetal move42 weeks gestation or the dates are un- ments daily after 24 weeks gestation. Volume of amniotic fluid should be certain, the decision to deliver should be made on the basis of antepartum test- assessed by palpation at all antenatal ing. All patients should record fetal visits, particularly at term and post movements and have immediate assess- term. Ultrasound examination should ment of fetal well-being if reduction of be performed if oligohydramnios is fetal movements is noted. Non-stress suspected. If the condition is contests, alternating with ultrasound ex- firmed, labour should be induced. If a pregnancy continues beyond 41 amination with biophysical profile every three to four days, will provide weeks, a non-stress test should be perreliable, though not infallible, monitor- formed. If the cervix is favourable at 42 ing. An abnormal non-stress test should be followed by ultrasound assessment weeks, induction of labour can be conof biophysical profile or contraction sidered. If it is unfavourable, bistress test. If the results are not reassur- weekly monitoring, using non-stress tests alternating with biophysical proing, labour should be induced. Patients with oligohydramnios dis- files, should be commenced. If either covered on physical examination, and test does not produce a reassuring reconfirmed on ultrasound examination sult, induction of labour is indicated. at term or post term, should undergo Induction should also be considered prompt induction of labour. In the pres- once the cervix becomes favourable. ence of variable decelerations on a non- Continuous internal fetal heart-rate stress test, ultrasound assessment of monitoring should be used in post-term volume of amniotic fluid is indicated, labour. If necessary, fetal scalp pH and U as oligohydramnios is almost always gases should be determined.

CAN. FAM. PHYSICIAN Vol. 34: SEPTEMBER 1988

Acknowledgement The secretarial assistance of Mrs.

Lydia Husak is greatly appreciated. References 1. Vorherr H. Placental insufficiency in relation to postterm pregnancyand fetal postmaturity. Am J Obstst Gynecol 1975; 123:67-103. 2. Chamberlain G, Philipp E, Howlett K, Masters , eds. British Births 1970. H. Obstetric Care. London, U.K.: William Heinemann Medical Books, 1978. 3. Gibb DMF, Cardozo LD, Studd JWW, Cooper DJ. Prolonged pregnancy: is induction of labour indicated? A prospective study. Br J Obstet Gynaecol 1982; 89:292-5. 4. Cole RA, Howie PW, MacNaughton MC. Elective induction of labour: a randomised prospective trial. Lancet 1975; 1:767-70. 5. Chalmers I, Zlosnik JE, Johns KA, Campbell H. Obstetric practice and outcome of pregnancy in Cardiff residents 1965-73. 6. MacKenzie IZ, Embrey MP. Cervical ripening with intracervical prostaglandin

E2 gel. Br Med J 1977; 2:1381-4. 7. Crowley P, O'Herlihy C, Boylan P.

Value of ultrasound measurement of amniotic fluid volume in the management of prolonged pregnancy. Br J Obstet Gynaecol 1984; 91:444-8. 8. Hauth JC, Goodman MT, Gilstrap LC, Gilstrap JER. Post-term pregnancy. I. Obstet Gynecol 1980; 56:467-9. 9. Boyd ME, Usher RH, McLean FH, Kramer MS. Obstetric consequences of postmaturity. Am J Obstet Gynecol 1988;

158:334-8.

10. Cardozo L, Fysh J, Pearce JM. Prolonged pregnancy: the management debate. Br Med J 1986; 293:1059-63. 11. Lagren DC, Freeman RK. Management of postdate pregnancy. Am J Obstet Gynecol 1986; 13:154-8. 12. Campbell S. Assessment of fetal development by diagnostic ultrasound. Clin Perinatol 1974; 1:504-19. 13. Warsof SL, Pearce JM, Campbell S. Place of routine ultrasound screening. 1983; 10:445-8. 14. Pearson J, Weaver J. Foetal activity and foetal well-being: an evaluation. Br Med J 1976; 1:1305-7. 15. Manning FA, Baskett TF, Morrison I, Lange I. Fetal biophysical profile scoring: a prospective study in 1184 high risk patients. AmnJ Obstet Gynecol 1981; 140:289.

2029