Spontaneous preterm delivery in pregnant diabetics

Preliminaiy note

J. Perinat. Med-

10 (1982; 249

Spontaneous pretenn delivery in pregnant diabetics:

A high risk hitherto

⁴⁽

uniecognized"

G. D. Roversi, E. Pedretti, M. Gargiulo, G. Tronconi*

* Institute of Obstetrics, Gynecology and Pediatrics, Regina Elena Midvives School University of Milan

It is well known that preterm delivery is more frequent in the pregnant diabetic (using WHO's definition of delivery before the 37 th completed week, i.e. before the 259 th day from the beginning of the last menstrual period). In most studies, data concerning the duration of the gestalion either have been summarily reported or unreported com- pletely. Moreover, the delivery occurring before the 37th week of pregnancy is sometimes defined äs "preterm" only in cases of newbora infants weighing less than 2500 g. Thus, the risk of pre- term delivery (PD) in pregnant diabetics has been underestimated. The risk of PD deserves close attention, considering that its incidence ranges from 50% to 80% or more (personal investigation in progress).

An even more serious consequence arises from the fact that cases of PD have not been classified into two groups: those due to labor with a Spontaneous onset and those due to artificially induced delivery, i.e. stimulated labor and/or cesarean section. One is inclined to think that artificially induced deliv- ery is by far the more common. In fact, in preg- nant diabetics a policy of early delivery is gener- ally followed considering the high risk of fetal death in the last month of pregnancy. In the last ten years considerable dinical research has been devoted to countering the expected adverse out- come of this policy, i.e. the risk of premature infants. This has required reliable tests of fetal well-being to be devised which enable the time of preterm delivery to be postponed. In contrast to what might be expected, the PD rate in pregnant

diabetics due to Spontaneous labor (spontaneous preterm delivery, SPD) is äs frequent, if not more frequent, than that due to artificially induced delivery (induced preterm delivery, IPD). This has been recendy pointed out by M^LSTED-PEDER- SEN in Copenhagen [5]. In cases of clinical dia- betes in ihe Copenhagen series, SPD rate is 29%

(a more accurate figure is obtained by subtracting the number of cases of IPD from the total: This brings the incidence of SPD up to 38%, 219/583;

see Tab. I. When subdivided into WHITE'S classes, the results are: B 21%, C 35%, D 26%, F 15%. The overall figure is thus six times the incidence of PD in generaL which is about 5-8% [l, 5]. The per- centage of IPD is lower, 22%; when subdivided into WHITE'S dasses this gives: B 15%, C 14%, D 20%, F 50%. The two groups together total 51%. This state of affairs has not changed with passing years: The flgures show little change from 1959 to 1977, and the internal ratio did not change during the period (57/43), see Tab. I.

Surprisingly enough, the SPD rate is also high in cases of gestational diabetes and, at 17% is three times higher than in the general obstetric popula- tion. From personal investigations, the data of other case studies at our disposal confirm to date the results of the Copenhagen series, with the largest differences noted in the incidence of IPD.

A different result emerges from our case study between 1963-1975. Insulin was adniinistered to the maximal tolerated dose both in cases of gestational and clinical diabetes. Pregnancy was aüowed to proceed until spontaneous labor which 0300-5577/82/0010-0249S02.00

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was allowed by surveillance of fetal well-being [for detaüs see reference 6, 7, 8, 9. 10, 11, 12].

The incidence of SPD is 6.7%: 7.1% in gestational diabetes and 6.1% in clinical diabetes (class B 4.5%, C 6.7%, D 4.8%, F 23.0%). Apart from class F, this means there is no difference from the PD rate in general. In only three cases (one of gesta- tional diabetes, two of class F diabetes) was delivery artificially induced before term. This slightly increases the total to 7.5% in gestational .and 7.2% in clinical diabetes (see Tab. I). M.

CHARTIER in Paris has given us the results of what we believe to be aunique experience [2]. Between 1962 and 1974, he administered insulin according to what he defines äs "classic criteria", i.e. the guidelines generally followed in treating pregnant diabetics. In cases of clinical diabetes the SPD rate was similar to that of the Copenhagen series, 25%.

In 1974 he began to adopt our therapeutic criteria.

The SPD rate feil dramatically to 5.7%. As during the same period DPD had been reduced to 8.6%, the total PD rate dropped from 85% in the first period to 14.3% in the second (see Tab. I). These results are an obvious confirmation of our own experience.

This brief report puts forward the following con- siderations:

l. PD must be considered a first-class risk in preg- nant diabetics. It occurs in 50—80% of the dia- betic population. In diabetic patients neonatal morbidity is still high [3]. As the morbidity is to

a great extent due to prematurity, its reduction closely depends on the substantial reduction of the above percentages.

2. Success will be somewhat incomplete if only prematurity due to artificially induced delivery is reduced. In fact, SPD occurs in about 30% of pregnant diabetics and accounts for half or more of PD in these patients. Therefore, the obstetrician should ascribe to SPD a risk that has hitherto been

"unrecognized", namely, the same concern which he has devoted so far to the risk of PD caused by prophylactic Interruption of pregnancy.

3. We have already stated [6, 7, 8, 9,10,12] that since 1963 we have abandoned the policy of early delivery in pregnant diabetics without having to report a single case of fetal death in utero. At the same time, äs is demonstrated in this communica- tion, the risk of SPD gave us little concern, äs its incidence was that generally accepted. This result is certainly attributable to the type of control of maternal diabetes we used, and the confirmation of CHARTIER's series supports this view. How and why can insulin therapy bring about such a radical reduction in the risk of SPD in pregnant diabetics?

Why in cases of slight metabolic derangement of the mother (gestational diabetes) is SPD rate three times higher than normal, äs MPLSTED-PEDER- SEN has shown? Our knowledge of the mechanism initiating term and preterm labor is too scarse to answer these questions [4]. Conversely, our knowl- edge of these mechanisms would be benefited if we could answer these queries.

Summary

Preterm delivery (PD) - before the 259th day from the beginning of the last menstrual period - is very frequent in pregnant diabetics (from 50% to 80% or more, perso- nal investigation in progress)* In these patients a policy is generally followed of a systematically controlled early delivery. Therefore, one is inclined to think that the high frequency of PD is rnainly the consequence of this policy.

However it has been recently pointed out [5] that spontaneous labor accounts for half or more of PD in pregnant diabetics. Morepver in pregnant women with gestational diabetes PD rate due to spontaneous kbor is three times higher than in the general obstetric popula-

tion [5]. A different result emerges from our case study, 1963-1975. Insulin was administered to the maximal tolerated dose both in case of gestational and clinical diabetes [l, 6, 7, 8, 9, 10, 11, 12]. The incidence of PD due to spontaneous labor is 6.7% (7.1% in gestational and 6.1% in clinical diabetes), i.e. no difference from PD rate in general. Since 1974 M. CHARTIER, Paris, has been adopting the same therapeutic criteria [2]. His results seem to confirm that the risk of PD due to spon- taneous labor drastically reduces in pregnant diabetics strictly controlled.

Keywords: Artificially induced delivery, diabetes in pregnancy, gestational diabetes, preterm delivery, spontaneous labor.

J. Perinat. Med. 10 (1982)

Zusammenfassung

Spontane Flühgeburten bei schwangeren Diabetikerinnen:

ein bisher falsch interpretiertes Risiko.

Bei schwangeren Diabetikerinnen kommt es sehr häufig (nach eigenen Untersuchungen in 50-80% der Fälle oder mehr) zu spontanen Frühgeburten, d.h. zur Geburt vor dem 259. Tag p.m. In der Praxis geht man im allgemeinen so vor, daß man bei diesen Patientinnen den Geburtster- min vorverlegt. Deshalb könnte man annehmen, die große Häufigkeit von Frühgeburten ist hauptsächlich Folge, die- ses Vorgehens. Vor kurzem ist aber gerade betont worden, daß es in mehr als der Hälfte der Fälle, wo es zu Frühge- burten kam, bei den schwangeren Diabetikerinnen spon- tane Wehen einsetzen [5]. Darüberhinaus treten bei Frauen mit einem Gestationsdiabetes spontane vorzeitige

Wehen dreimal häufiger auf als in einem Normalkollektiv [5]. Unsere Untersuchungen aus dem Zeitraum von 1963 bis 1975 zeigen jedoch ein anderes Ergebnis: sowohl beim Gestationsdiabetes wie auch beim klinischen Diabetes haben wir Insulin bis zur maximal tolerierten Dosis verab- reicht [l, 6, 7, 8, 9,10,11,12]. Die Häufigkeit von Früh- geburten nach vorzeitigen Wehen betrug 6,7% (7,1% beim Schwangerschaftsdiabetes und 6,1% beim klinischen Dia- betes), also kein Unterschied zur üblichen Frühgeburten- rate. Seit 1974 verfährt Dr. CHARTIER in Paris nach den gleichen therapeutischen Kriterien [2]. Seine Ergebnisse scheinen zu bestätigen, daß sich das Risiko von Frühge- burten wegen spontaner vorzeitiger Wehen bei strengster Überwachung der schwängeren Diabetikerinnen drastische reduzieren läßt.

Schlüsselwörter: Eingeleitete Geburt, Diabetes in der Schwangerschaft, Gestationsdiabetes, Frühgeburt, spontane Wehen.

Resume

L'Accouchement premature spontane chez les diabetiques:

Un haut risque jusqu'alors „masque".

L'accouchement piemature (AP) — avant le 259eme jour compte a partir du premier jpur des dernieres regles — est tres fr6quent chez la diabetique (50 a 80% ou plus, en augmentation selon les observations de l'auteur). En regle generale, chez ces patientes une politique de surveilknce systematique est appliquee jusqu'au momentdel'accouch- ement. En consequence, on est indte a penser que k grande frequence d'AP provient principalement de cette attitude.

Toutefois, il a ete recemment mis en evidence [5] que le declenchement spontane du travail se produit chez k moitie ou plus des AP des diabetiques. En outre, chez les femmes enceintes presentant un diabete gestationnel le pourcentage d'AP secondaire a un declenchement

spontane du travail est trois fois plus eleve que dans k Population generale des femmes enceintes [5]. Des fesultats differents ressortent de Fetude de nos cas entre 1963 et 1975. L'insuline a ete injectee ä k dose maximale toleree a k fois dans les cas de dkbetes gestationnels et dans les cas de dkbetes cliriiqües [l, 6, 7, 8, 9,10,11,12].

L'incidence de secondaire au declenchement spontane .du travail est de 6,7% (7,1% ppur les diabetes gestationnels et 6,1% pour les dkbetes cliniques) c'est-a- dire sans difference avec k frequence de dans k popuktion generale. Depuis 1974, le Dr. CHARTIER, a Paris, a adopte les memes criteres therapeutiques [2].

Ses resultats semblent confirmer que le risque d'AP secondaire au declenchement spontane du travail diminue considerablement au cours des grossesses des diabetiques rigoureusement contrölees.

Mots-cles: Declenchement de l'accouchement, diabete au cours de k grossesse, dkbete gestationnel, accouchement premature, accouchement spontane.

Bibliography

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Received February 21,1982. Accepted June 10,1982.

G. D. Roversi Via E. Besana 6

1-20122 Milan/Italy

J. Perinat. Med. 10(1982)