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 Quotes and Excerpts from www.eObGynNews.com and 
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 safety, complications & practice trends for obstetricians  

Bibliography, Recommended Reading and Scientific Citation from obstetrical sources for the:

Ultrasound Limitations /Misapplication of Findings

 

Ultrasound Comparable to Educated Guess in Predicting Birth Weight; Ob.Gyn.News Oct 1, 2002

Practice the “Art” of Estimating Fetal Weight, Ob.Gyn.News; Sept 15 2003 Vol 38, No 18

 

Estimated Fetal weight Not a Guide for Cesareans – preventing shoulder dystocia; Dec 15, 2001, Vol 36, No 24

 

Fetal Weight Does Not Help Predict VBAC Success – using weight estimates to determine who gets a trial of labor ‘is not justified’ / Induction vs spontaneous labor; Ob.Gyn.News; Jul 15 2001 Vol 36

Ultrasound Comparable to Educated Guess in Predicting Birth Weight  Head-to-head comparison
October 1 2002 • Volume 37 • No 19

A guess is nearly as good in predicting birth weight at term as estimates based on ultrasound measurements or maternal characteristics, Dr. Gerard G. Nahum said at the annual meeting of the American College of Obstetricians and Gynecologists.  A head-to-head comparison of various methods of predicting birth weight at 37-42 weeks of gestation in 81 nondiabetic gravid women found that none of 20 ultrasound fetal biometric algorithms was significantly more accurate than guesses based on population-specific birth weights or estimates based on maternal characteristics, said Dr. Nahum of Duke University, Durham, N.C.

Practice the “Art” of Estimating Fetal Weight; Ob.Gyn.News; Sept 15 2003 Vol 38, No 18

Put down your clipboard and use your hands and expertise to estimate fetal weight when managing a patient with a large fetus, Dr William GIlbert said. Ultrasound is "awful" for detecting macrosomia but many clinicians have stopped estimating fetal weight themselves because ultrasound is available, he said at a meeting on antepartum and intrapartum management sponsored by the University of California, San Francisco. 

"We're all so busy running in and out of exam room that we've lost quite a bit of that art of estimating fetal weight," said Dr Gilbert, chief of maternal-fetal medicine and professor of ob.gyn at the University of California, Davis. 

Only 65% of fetal weights estimated by ultrasound are within 10% of the actual birth weight. 

There is very good (level A) evidence that for suspected fetal macrosomia [large baby], ultrasound is no better than clinical palpation (leopold's maneuvers) for estimating fetal weight, according the the American College of Obstetricians and Gynecologists (ACOG) Practice Bulletin No 22, issued in 2000. 

Vaginal delivery is a reasonable option for fetuses weighing up to 5 kg [11  pounds] in nondiabetic women. Avoid forceps and vacuum extraction in women at high risk for macrosomia. 

Estimated Fetal weight Not a Guide for Cesareans – preventing shoulder dystocia; Dec 15, 2001, Vol 36, No 24

Estimated fetal weight can be used as a guidepost in directing obstetric management …but should not be used to dictate cesarean sections, researcher determined in a 4-year study.

 

Among 118 women with an estimated fetal weight (EFW) of at lest 4500 g [9# 15ozs] 63 elected to have a cesarean section for macrosomia. Vaginal delivery was accomplished in 34 of the 56 of those who labored, and there were 2 shoulder dystocias. [22 had] Cesareans performed during labor.

 

If all of the women in this group had undergone Cesareans, 32 unnecessary operations would have been performed to prevent 2 shoulder dystocias [NNT ratio of 16 to 1] Dr Mullin said.  Analysis of the other group shows that 28 (of 62) women who elected to undergo Cesareans delivered babies smaller than there estimated fetal weight.  

 

…if all 62 had undergone a trial of labor instead of a cesarean, …47 would have delivered vaginally. It is estimated that 7 shoulder dystocias were prevented … but 40 cesareans were performed unnecessarily. Applying historic rates of brachial plexus injury [Erb’s Palsy of the arm, a complication of shoulder dystocia] Dr Mullin estimated that 133 to 522 Cesareans would have to be performed to prevent one permanent brachial nerve injury.

 

He concluded that estimated fetal weight can be used to guide management but should not dictate Cesarean delivery.   

Fetal Weight Does Not Help Predict VBAC Success; Using weight estimates to Determine who gets a Trial of Labor“ Not Justified” – Induction vs. Spontaneous Labor;  July 15, 2001, Vol 36, No 14

Fetal weight estimates based on ultrasound are not useful in determining which women with a history of C-section due to cephalopelvic disproportion should undergo a trial of labor…

 

Contrary to widespread practice [!], estimating the size of the fetus and comparing it to that of the [previous] neonate should not be used as a risk factor ……. Dr. Para said at the annual meeting of the Society of Obstetricians and Gynecologist of Canada.

 

Dr Pare of the University of Pennsylvania and her associates studied the medial records of 1,176 women who attempted VBAC at 17 medical centers.

 

“We could not identify a cut off that yielded an acceptable trade-off between sensitivity and specificity, Dr Pare said. And in the end, looking at fetal weight, weight difference between the [first] neonate and the current fetus “is no better than flipping a coin.” She said.

 

On the basis of this study, it appears that ultrasound at term to measure fetal weight and to determine who is eligible for a trial of labor “is not justified,” Dr Para said.

 

What does appear to be predictive of a women’s success at VBAC is whether labor is induced or spontaneous according to … a second study presented at the meeting. 

 

In that study Dr. Tina Delaney and her associates at Dalhousie University, Halifax N.S, compared the medical records of 2,943 women who went into spontaneous labor with those of 803 who were induced. All the women underwent a trial of labor and had one previous C-section

 

Of the women who were induced, 38% were delivered by C-section compared with 24% of the women in the spontaneous labor group [63% normal birth rate for induction compared with 76% for spontaneous labor]

 

In addition, early postpartum hemorrhage rates were 7.4% for those induced and 5% for spontaneous labor… rates of neonatal intensive care admission were 13% for induced and 9% for spontaneous labors…

 

Even when the data were adjusted for various risk factors, women who were induced had nearly double the risk of having a C-section, compared with those who delivered spontaneously. Although the incidence of uterine rupture was not large enough in absolute term to yield statistically significant differences, the rate in the induced group was about double that of spontaneous labor (0.7% vs. 0.3%)

 

Uterine rupture was approximately twice as likely in the prostaglandin group, compared with the oxytocin group….