General Obstetrics and Gynecology Obstetrics
Hypertensive disorders in twin versus singleton gestations,☆☆

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Abstract

Objective: This study was undertaken to compare rates and severity of gestational hypertension and preeclampsia, as well as perinatal outcomes when these complications develop, between women with twin gestations and those with singleton gestations. Study Design: This was a secondary analysis of prospective data from women with twin (n = 684) and singleton (n = 2946) gestations enrolled in two separate multicenter trials of low-dose aspirin for prevention of preeclampsia. End points were rates of gestational hypertension, rates of preeclampsia, and perinatal outcomes among women with hypertensive disorders. Results: Women with twin gestations had higher rates of gestational hypertension (relative risk, 2.04; 95% confidence interval, 1.60-2.59) and preeclampsia (relative risk, 2.62; 95% confidence interval, 2.03-3.38). In addition, women with gestational hypertension during twin gestations had higher rates of preterm delivery at both <37 weeks’ gestation (51.1% vs 5.9%; P < .0001) and <35 weeks’ gestation (18.2% vs 1.6%; P < .0001) and also had higher rates of small-for-gestational-age infants (14.8% vs 7.0%; P = .04). Moreover, when outcomes associated with preeclampsia were compared, women with twin gestations had significantly higher rates of preterm delivery at <37 weeks’ gestation (66.7% vs 19.6%; P < .0001), preterm delivery at <35 weeks’ gestation (34.5% vs 6.3%; P < .0001), and abruptio placentae (4.7% vs 0.7%; P = .07). In contrast, among women with twin pregnancies, those who remained normotensive had more adverse neonatal outcomes than did those in whom hypertensive complications developed. Conclusions: Rates for both gestational hypertension and preeclampsia are significantly higher among women with twin gestations than among those with singleton gestations. Moreover, women with twin pregnancies and hypertensive complications have higher rates of adverse neonatal outcomes than do those with singleton pregnancies. (Am J Obstet Gynecol 2000;182:938-42.)

Section snippets

Material and methods

The study population consisted of healthy women with either singleton or twin gestations who were enrolled in two separate multicenter randomized trials comparing low-dose aspirin with placebo for the prevention of preeclampsia.6, 7 The trials were designed and conducted by members of the Network of Maternal-Fetal Medicine Units for the National Institute of Child Health and Human Development. The subjects for one of the trials were healthy nulliparous women with singleton pregnancies who were

Results

Table I describes the baseline characteristics at the time of random assignment for women with singleton and twin gestations.

. Baseline clinical characteristics

Empty CellTwin gestations (n = 684)Singleton gestations (n = 2946)Statistical significance
Maternal age (y, mean ± SD)25.0 ± 6.020.4 ± 4.6P < .0001
Systolic blood pressure (mm Hg, mean ± SD)110 ± 11106 ± 11P < .0001
Diastolic blood pressure (mm Hg, mean ± SD)63 ± 9.161 ± 9.0P < .0001
Smoking during pregnancy (%)14.511.0P = .0100
Nulliparous (%)38.9100P

Comment

Several studies have described the risk factors and the incidences of hypertensive disorders among women with twin pregnancies as compared with those among women with singleton pregnancies.1, 2, 3, 4, 5 Most of these studies are hospital-based, however, and thus their findings are affected by selection bias because women with these obstetric complications are more likely to be referred to tertiary medical centers.1, 2, 3 Only two studies evaluated women prospectively from <24 weeks’ gestation

Acknowledgements

`The National Institute of Child Health and Human Development Network of Maternal-Fetal Medicine Units was established by the Institute in 1986. In addition to the authors the members of the Network and their institutional affiliations are as follows: J. Harger, M. Cotroneo, and T. Kamon, Magee-Women’s Hospital, Pittsburgh; B. Mercer and R. Ramsey, University of Tennessee, Memphis; Y. Rabello, D. McCart, and E. Mueller, University of Southern California, Los Angeles; R. Goldenberg and R.

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Supported by grants HD19897, HD21410, HD21414, HD21434, HD27860, HD27861, HD27869, HD27883, HD27889, HD27905, HD27915, and HD27917 from the National Institute for Child Health and Human Development.

☆☆

Reprint requests: Baha M. Sibai, MD, Department of Obstetrics and Gynecology, University of Tennessee, Memphis, 853 Jefferson Ave, Room E102, Memphis, TN 38103.

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