Wednesday, March 5, 2008

Put that in your "big baby" pipe and smoke it!

Doctors love to pull the "big baby" card these days. Frequently, the mother gets pinned with gestational diabetes whether or not she passed the glucose tolerance test (GTT) if her baby is more than about 8.5 lbs. Some doctors even go so far as to recommend a c/s even in first-time moms or moms who've delivered vaginally before if they suspect a "big baby". Here's the fly in that ointment:

J Obstet Gynaecol. 2007 May;27(4):374- 8. Recurrence of fetal macrosomia in
non-diabetic pregnancies.

Walsh CA, Mahony RT, Foley ME, Daly L, O'Herlihy C.
National Maternity Hospital Dublin, Ireland.

Fetal macrosomia (birth weight >/=4,500 g) is known to increase a number of
adverse maternal and perinatal outcomes. Although there is a clear
association between maternal diabetes mellitus and fetal macrosomia, the
majority of macrosomic infants are born to non-diabetic mothers. We wished
to determine the recurrence rate of macrosomia in non-diabetic pregnancy and
to see if a history of multiple prior macrosomic infants confers additional

A retrospective analysis of 14,461 term, singleton, infants born to
non-diabetic mothers in 1997 and 1998 was performed, using a computerised
hospital database. Among 14,461 term pregnancies, 529 infants (3.7%) were
macrosomic, and the incidence was significantly higher in parous women
(4.6%) compared with nulliparas (2.4%, p < 0.0001).

Over the next 5 years, 164 of these women returned for another delivery.
Women with a history of one macrosomic infant are at significantly increased
risk of another macrosomic infant in a subsequent pregnancy (OR 15.8, 95% CI
11.45 - 21.91, p < 0.0001). For women with two or more macrosomic infants,
the risk is even greater (OR 47.4, 95% CI 19.9 - 112.89, p < 0.0001).
Macrosomia was associated with increased rates of instrumental delivery and
anal sphincter injury regardless of parity, and additionally with increased
rates of caesarean delivery and shoulder dystocia among nulliparas.

Overall, 88% of women who laboured with a macrosomic infant achieved vaginal

Hmm. 88% of women achieved vaginal delivery. Sounds perfectly sensible to me and well within the WHO guidelines that c/s is necessary in 10-15% of births.

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