Fertility treatment and oral contraceptive discontinuation for identification of pregnancy planning in routinely collected health data – an application to analgesic and antibiotic utilisation

Table 1 Characteristics of the included pregnancies by proxies of pregnancy intention^a,b

	Fertility treatment (n = 19,449)	Timing of oral contraceptive discontinuation
	Fertility treatment (n = 19,449)	Early (n = 77,735)	Late (n = 42,621)	Within-pregnancy (n = 32,780)
Maternal age	31.8 (5.0)	28.9 (4.7)	28.4 (4.6)	27.7 (4.9)
Married/cohabiting	95.3	94.4	94.9	92.4
Employed	73.2	74.1	75.5	72.1
Nulliparous	58.2	55.3	57.6	59.4
Previous pregnancy loss	27.5	19.9	10.8	9.9
Obstetric comorbidity index^c	0.77 (1.2)	0.39 (0.8)	0.36 (0.8)	0.35 (0.9)
Components of the index
Asthma	5.3	5.2	5.3	5.4
Diabetes, pre-gestational	1.2	0.7	0.7	0.7
Hypertension, chronic	0.9	0.5	0.4	0.4
Hypertension, gestational	2.5	2.1	2.1	1.9
Kidney disease	0.6	0.7	0.7	0.6
Multiple gestation	5.6	1.3	1.3	1.2
Preeclampsia, mild	3.0	2.0	2.1	2.1
Preeclampsia, severe	2.1	1.2	1.3	1.6
Previous caesarean section	5.5	5.3	4.6	3.6
Rheumatoid arthritis	0.7	0.4	0.4	0.3
Folic acid use
Initiation before pregnancy	51.0	35.3	32.9	25.4
Initiation during pregnancy	31.4	43.4	44.9	49.1
No folic acid	17.7	21.6	22.2	25.5
Smoking in early pregnancy	5.4	8.1	7.9	9.9
Smoking at the end of pregnancy	3.3	4.6	4.5	5.4
Weight gain in pregnancy	13.8 (7.7)	14.6 (8.5)	14.6 (7.3)	14.9 (7.9)

^a Table stratified by folic acid use is shown in Additional file 1
^bFigures shown are percent of non-missing values with the exception of maternal age, calendar year, obstetric comorbidity index, and weight gain in pregnancy, presented as mean (standard deviation). Missing values ranged from 0% (maternal age, calendar year, parity) to 17.6% (maternal employment). Women could choose not to have smoking and weight reported to the MBRN. For smoking, 12.4 to 16.3% chose not to report. For weight, 75.9 to 77.7% chose not to report
^cAdapted from Bateman et al. [24], using the variables available in MBRN (age, asthma, pre-gestational diabetes, chronic hypertension, kidney disease, previous caesarean section, multiple gestation, severe preeclampsia, mild preeclampsia, gestational hypertension) and weighting the variables as done by Bateman et al. [24].

ISSN: 1471-2393