Definitions

Table

Definitions

Medical risk factors

Anaemia, cardiac disease, acute or chronic lung disease, diabetes, genital herpes, hydramnios/oligohydramnios, haemoglobinopathy, chronic hypertension, pregnancy associated hypertension, eclampsia, incompetent cervix, previous infant ³ 4000 g, previous preterm or small for gestational age infant, renal disease, Rh sensitisation, uterine bleeding.

Complications of labour or delivery

Febrile, meconium moderate/heavy, premature rupture of membrane, abruptio placenta, placenta previa, other excessive bleeding, seizures during labour, precipitous labour, prolonged labour, dysfunctional labour, breech/malpresentation, cephalopelvic disproportion, cord prolapse, anaesthetic complication, fetal distress.

Table: Adjusted odds ratios (95% confidence intervals) for primary caesarean delivery for mothers with no indicated risk factors†: United States, 1991, 1996, and 2001

	All mothers	First time mothers
Year
2001	1.49** (1.47 to 1.50)	1.46** (1.44 to 1.48)
1996	0.99 (0.98 to 1.00)	0.99 (0.97 to 1.00)
1991	1.00	1.00
Race/ethnicity
White non-Hispanic	1.00		1.00
Hispanic	1.54** (1.52 to 1.55)		1.65** (1.63 to 1.68)
Black non-Hispanic	1.79** (1.76 to 1.81)		1.80** (1.77 to 1.84)
Native American	0.98 (0.92 to 1.03)		1.08* (1.00 to 1.17)
Asian or Pacific Islander	1.12** (1.10 to1.14)		1.10** (1.07 to 1.13)
Age
20-24	1.00	1.00
25-29	1.47** (1.45 to 1.49)	1.65** (1.62 to 1.67)
30-34	1.91** (1.88 to 1.93)	2.30** (2.26 to 2.34)
35-39	2.62** (2.58 to 2.66)	3.58** (3.49 to 3.66)
³40	3.85** (3.74 to 3.96)	5.42** (5.16 to 5.70)
Education (years)
<12 years	1.00	1.00
12 years	1.22** (1.21 to 1.24)	1.21** (1.19 to 1.23)
³13 years	1.15** (1.14 to 1.17)	1.08** (1.06 to 1.10)
Birth weight (g)
<2500	1.63** (1.59 to 1.67)	1.40** (1.36 to 1.45)
2500-3999	1.00	1.00
³4000	2.23** (2.21 to 2.26)	2.76** (2.72 to 2.81)
Parity
1	1.00	–
³2	0.27** (0.27 to 0.28)	–

Source: Natality Data Sets: 1991, 1996, 2001. National Center for Health Statistics.

†Full term, singleton, vertex births with no medical risk factors or complications of labour or delivery reported on the birth certificate.

*P<0.05.

**P<0.0001.

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