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Cardiotocography and diabetic pregnancy

JB Sharma,Manu Goyal  ( Department of Obstetrics & Gynecology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India. )

September, 2016

Abstract

Foetal monitoring in antenatal period and during labour is done to detect foetal distress and to take necessary action timely in order to improve perinatal outcome. Maternal awareness of foetal movement is routinely recommended in all pregnancies after 28 weeks gestation. In high risk pregnancies like diabetes, foetal growth restriction, macrosomia, additional means of foetal surveillance should be used like antenatal cardiotocography, non stress test, biophysical profile or Doppler studies. Diabetic mothers are at increased risk for sudden intrauterine foetal demise, thereby mandating the need of cardiotocography and ultrasound biophysical profile testing weekly or twice weekly in such patients. Foetal surveillance in diabetic patients in low resource settings demands for frequent antenatal visits and non stress test if possible. During labour also, there should be continuous electronic foetal monitoring in diabetic mothers in both first and second stages of labour for early detection of foetal hypoxic stre s and timely intervention.
Keywords: Cardiotocography, Diabetes, Foetal surveillance, Antenatal, Intrapartum.

Introduction
Assessment of foetal well being is very important during the antenatal period. It needs additional testing when pregnancy is complicated by medical disorders in the mother and conditions affecting foetal health. Maternal diabetes is one such condition which exposes the foetus to increased morbidity and mortality, thus advocating additional testing for foetal well being. Uncontrolled diabetes has profound effects on embryogenesis, organogenesis, and foetal growth. Preconception control of diabetes and monitoring throughout pregnancy are important in reducing the impact of diabetes on the foetus and newborn. 1
Foetal well being assessment should be done to detect foetal hypoxic stress which may lead to foetal or neonatal death, and neurological damage. There are many ways to do foetal surveillance. These include daily foetal movement count, electronic foetal monitoring by non-stress test (NST), cardiotocography (CTG), contraction stress test (CST), biophysical profile (BPP) and; uterine and umbilical artery Doppler.

Cardiotocograph (CTG)
It is a continuous electronic record of foetal heart rate and uterine activity obtained by ultrasound transducer probes placed on maternal abdomen (external or indirect CTG). It can be traced on a paper strip or displayed on the monitor of the machine. Cardio-tocography also records uterine contractions along with the foetal heart rate thereby allowing assessment of the relationship between the two. An alternative means of monitoring the baby\'s heart rate with the CTG machine is to attach an electrode directly to the baby\'s presenting part, usually its head. This form of continuous monitoring is known as \'internal CTG\' and requires a ruptured amniotic sac (either spontaneously or artificially) and a scalp electrode (clip) attached to the baby\'s head.2


When foetal heart rate is monitored alone it is termed as non-stress test and when it is done with stimulation of uterine contractions to see the foetal heart response, it is termed as contraction stress test. Antenatal CTG is dependent on the maturation of foetal autonomic nervous system so it should be performed till after 28 weeks of gestation for foetal well being. Foetal hypoxia leads to certain adaptations which in turn cause changes in the foetal heart rate parameters. 3
Accepted normal parameters for the term foetus are reported as follows (Gribbin 2006; RCOG 2001).4,5
1. Baseline foetal heart rate of 110 to 160 beats per minute.
2. Baseline variability should be greater than five beats per minute.
3. Presence of two or more accelerations of the foetal heart rate exceeding 15 beats per minute, sustained for at least 15 seconds in a 20-minute period - this pattern is termed reactive.
4. Absence of decelerations.

Diabetes in pregnancy leads to increased incidence of macrosomia, IUGR in cases of associated pre-eclampsia or vasculopathy, congenital foetal malformations, and sudden intrauterine death. This is due to maternal hyperglycaemia leading to foetal hyperglycaemia, hyperinsulinaemia, hypertriglyceridaemia and macrosomia. There is sudden foetal death in diabetic patients due to oxidative stress, foetal hypoxia and acidosis, and free radical injury. Data suggests that there is as much as five times increased risk of stillbirth and perinatal mortality in patients with insulin dependent diabetes than in the general population. Therefore, it demands for extra and additional testing to assess the foetal status thereby allowing for timely detection of foetal compromise. This is achieved by non-stress test (NST) and biophysical profile repeated twice a week or every 72 hours.6 No single test alone is sufficient for foetal surveillance. There should be a combination of subjective maternal counting of foetal movement, NST and ultrasound biophysical profile. A normal NST is predictive of good perinatal outcome for one week (provided the maternal-foetal condition remains stable), except in women with insulin dependent diabetes or with a postdates pregnancy, in which case NSTs are recommended at least twice weekly. There is consensus that women who require insulin for treatment of GDM should undergo twice weekly heart rate testing after 32 weeks. While in patients with nephropathy, vascuolpathy and foetal growth restriction, it should begin as early as 28 weeks gestation. A normal BPP score along with a reactive NST is an indication of foetal well-being. The BPP provides 2 points each for foetal breathing, movement, and foetal tone in 30 minutes and 2 points for normal amniotic fluid volume. A total biophysical score of <4 is abnormal and suggestive of foetal compromise and increased risk of adverse outcome. People have also studied the role of Doppler umbilical blood flow measurement in women with GDM for foetal assessment with the main role being in growth restricted foetuses in diabetic women.2 Type and frequency of foetal surveillance should be individualised depending on the severity of maternal hyperglycaemia or presence of other adverse factors (Table-1)


SOGC (Society of Obstetricians and Gynecologists of Canada, 2007) suggests insulin-requiring GDM is one such condition where additional foetal surveillance both antenatally and intrapartum may be beneficial. SOGC has given classification of antepartum CTG or non-stress test as shown in Table-2


ACOG (American College of Obstetricians and Gynecologists, 2014) recommends initiation of antenatal foetal testing at 32 to 36 weeks of gestation in diabetic pregnancy requiring insulin that are well controlled and are otherwise uncomplicated.
International Diabetes Practice Guideline 2003 recommends that foetal kick count monitoring should begin from 28 weeks, and NST from 34 weeks in women with GDM.7
The negative predictive value of NST alone for predicting stillbirth within 1 week of a normal test is 99.8%; for BPP, modified BPP, and CST, it is greater than 99.9%. The false negative rate of antenatal testing (i.e. NST and amniotic fluid index) is 0.8 per 1000 women tested. About 60% who delivered because of abnormal testing showed no evidence of short-term or long-term foetal compromise. Non reactive NST has a low sensitivity and positive predictive value of 40% and 28% respectively to identify population at risk so it cannot be used as stand-alone test. Continuous CTG can prevent one death in one thousand births (0.1%).8

Intrapartum CTG
Diabetes is a high risk medical condition complicating pregnancy and it adversely affects both antepartum and intrapartum period of the foetus thereby necessitating strict monitoring. We have explained the role of cardiotocography during antepartum period. Now, we will discuss foetal monitoring in diabetic women during labour.
When a diabetic women comes in labour, there is recommendation to do admission foetal heart test as compared to no indication in low risk pregnancy.8 Foetal monitoring in labour can be electronic or manual intermittent auscultation. There is a consensus in the guidelines from professional bodies that the foetal heart should be auscultated at least every 15 minutes in the first stage of labour and at least every five minutes in the second stage of labour (ACOG 2014; Liston 2002; NCCWCH 2008; RANZCOG 2002) with each auscultation lasting at least 60 seconds.2 Electronic foetal monitoring is recommended for pregnancies at risk of adverse perinatal outcomes.7 In diabetes, continuous electronic foetal monitoring is recommended to detect foetal hypoxic distress and timely intervention. The absence of foetal heart rate reactivity and presence of decelerations is predictive of foetal distress in labour requiring caesarean section (Table-3)

USG measurement of amniotic fluid does not have a significant role in predicting foetal distress during labour in diabetic patients.
CTG changes in pregnancies complicated by diabetes are: reduced short term foetal heart rate variability, reduced foetal movements, longer episodes of low variation and reduced reactivity.9

CTG in Diabetic Ketacidosis
Continuous foetal monitoring is mandatory to assess foetal wellbeing. A non-reactive foetal heart tracing, repetitive late decelerations, or a non-reassuring biophysical profile may be present indicating some degree of foetal compromise in the ketoacidotic patient but they are not necessarily indications for immediate delivery.10

Conclusion
Diabetic mothers whether gestational or pre-pregnancy, are at high risk for adverse foetal and neonatal outcome, thus requiring additional testing for foetal monitoring in antenatal and intrapartum period. In low resource settings, the antenatal visits of diabetic women should be more frequent in third trimester as weekly or sometimes twice weekly to assess the foetal heart and growth at each visit. Women should be counseled regarding strict foetal kick counting and reporting if abnormal. In such settings, health care personnel should see the record of subjective foetal movement monitoring by women weekly at antenatal visit. If CTG machines are not available, foetal heart should be auscultated for any accelerations during foetal movement perceived by the woman. During labour, intermittent auscultation every 10-15 minutes in first stage and every 4-5 minutes in second stage is recommended if electronic foetal monitoring is not possible in the peripheral set-up.

References
1.Barnes-Powell LL. Infants of diabetic mothers: the effects of hyperglycemia on the fetus and neonate. Neonatal Netw 2007; 26: 283-90.
2.Grivell RM, Alfirevic Z, Gyte GML, Devane D. Antenatal cardiotocography for fetal assessment. Cochrane Database Sys Rev 2015: CD007863.
3.American College of Obstetricians and Gynecologists. ACOG technical bulletin: antepartum fetal surveillance, number 9, October 1999. Int J Gynecol Obstet 1994; 44: 289-94.
4.Gribbin C, Thornton J. Critical evaluation of fetal assessment methods. In: James DK (eds.), et al. High risk pregnancy management options, 3rd edition. Philadelphia, USA: Elsevier, 2006.
5.Royal College of Obstetricians and Gynecologists. The use of electronic fetal monitoring - the use and interpretation of cardiotocography in intrapartum fetal surveillance, Evidence based Clinical Guideline Number 8. London: RCOG Press, 2001.
6.Nageotte MP. Antenatal testing: diabetes mellitus. Semin Perinatol 2008; 4: 269-70.
7.American College of Obstetricians and Gynecologists. Practice bulletin number 145: antenatal fetal surveillance. Obstet Gynecol 2014; 124: 182-192.
8.Society of Obstetricians and Gynecologists of Canada. Fetal health surveillance: antepartum and intrapartum. JOGC 2007; 29: 1-56.
9.Buscicchio G, Gentilucci L, Giannubilo SR, Tranquilli AL. Computerized analysis of fetal heart rate in pregnancies complicated by gestational diabetes mellitus. Gynecol Endocrinol 2010; 26: 270-4.
10.Kamalakannan D, Baskar V, Barton DM, Abdu T. Diabetic ketoacidosis in pregnancy. Postgrad Med J 2003; 79: 454-7.


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