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Endothelium-derived nitric oxide is proposed to play an important role in the lowering of peripheral vascular resistance in normal pregnancy. In women with preeclampsia, the function of the endothelium is compromised, and it is suggested that reduced nitric oxide synthesis may contribute to the elevation of blood pressure and activation of coagulation pathways. In this study, we have compared responses to increments of intraluminal flow, considered to be a physiological stimulus to nitric oxide release, in arteries from normotensive nonpregnant and pregnant women and women with preeclampsia. Small subcutaneous arteries from normotensive pregnant women showed substantial flow-induced relaxation, which was attenuated by the nitric oxide synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) (mean relaxation, 48.3+/-8.0% [absence of L-NAME] versus 19.2+/-10.6% [presence of L-NAME]), whereas those from nonpregnant women and women with preeclampsia demonstrated modest constriction (mean constriction, 10.1+/-7.3% and 1.2+/-7.2%, respectively). Shear stress, the frictional force that is the stimulus for flow responses, was calculated from parameters of flow, viscosity, and artery diameter. Arteries from pregnant women showed greater relaxation to shear than those from nonpregnant women or those with preeclampsia. We conclude that flow-induced shear stress is a potent stimulus to vasodilatation in arteries from pregnant women and that this mechanism may lead to a fall in peripheral vascular resistance in normal pregnancy. Failure of this flow-induced dilatation may contribute to the gestational hypertension of preeclampsia.

1. The mechanisms of vascular adaptation to pregnancy remain to be fully elucidated. In this study we have compared flow-induced dilatation and myogenic responses in fifth generation mesenteric arteries from late pregnant and non-pregnant Wistar rats. 2. Myogenic tone, assessed as the difference between internal diameter (i.d.) in the presence and absence of external calcium, at each of six transmural pressure steps (40-90 mmHg) was no different in arteries from pregnant and non-pregnant animals (90 mmHg; pregnant animals, 20.5 +/- 3.2% change in i.d., n = 13; non-pregnant animals, 14.4 +/- 4.4% change in i.d., n = 13; n.s.). 3. Flow-induced dilatation was significantly increased in arteries from pregnant animals when compared with that in non-pregnant animals (pregnant, 11.2 +/- 3.7% increase in i.d., n = 12; non-pregnant, 1.2 +/- 1.0%, n = 8; P < 0.02; at the maximal flow rate of 1.46 microliters s-1). 4. Flow-induced dilatation was significantly reduced in arteries from pregnant rats after incubation with the nitric oxide synthase inhibitor N omega-nitro-L-arginine methyl ester (11.2 +/- 3.7% increase in i.d. vs. 0.8 +/- 1.5% with L-NAME, n = 12, at a flow rate of 1.46 microliters s-1; P < 0.02), but not altered in non-pregnant rats (1.2 +/- 1.0% vs. 1.4 +/- 1.5% with L-NAME, n = 8; n.s.). This was also reflected in a greater response to shear stress in the arteries from pregnant animals. 5. We conclude that myogenic tone is not significantly different in pregnant and non-pregnant resistance sized mesenteric arteries of Wistar rats. However, flow-induced dilatation, mediated by nitric oxide release, may play a major role in lowering vascular resistance during pregnancy.

Objective: To evaluate a multidisciplinary women-only clinic (WOC) providing HIV testing, HIV follow-up, genitourinary screening and a substance misuse service. The clinic is designed to attract women who are at risk of acquiring sexually transmitted infections, including HIV, yet are not using existing medical services., Design: A questionnaire survey and review of the case notes of women attending the WOC during the first seven months (April to October 1991) and comparison with a mixed-sex, daytime genitourinary clinic (John Hunter Clinic), and a HIV out-patients clinic (Kobler Centre) all within St Stephen's Clinic., Results: One hundred and twenty-nine women attended the WOC over the seven month period and 113 completed a questionnaire. The main reasons for attendance included a preference to be seen by a female doctor and staff, the presence of female patients in the waiting area, and the greater convenience of an evening clinic. In the absence of the WOC over half the patients (56%) indicated that they would not have attended a genitourinary medicine (GUM) clinic. The WOC attracted significantly more new patients than in the JHC (31.5% vs 15% p < 0.001). One hundred and four women (81%) were screened for genitourinary infection. Compared with the JHC there were significantly more cases of genital warts (33.9% vs 16.1% p < 0.001) and candidosis (41.5% vs 22.3% p < 0.001). A greater number of HIV tests were also performed (19% vs 9% p < 0.01). Sixteen (12.4%) women were HIV positive. Their attendance record at both first appointment (88% vs 64% p < 0.05) and subsequent follow-up appointments (81% vs 43% p < 0.05) was significantly higher than a comparable group of women seen by the same doctor (FB) in the Kobler Centre. The women also saw the health adviser more frequently. Although the number of injecting drug users was small (eight), all women currently injecting drugs entered a detoxification programme., Conclusion: The WOC has become an established and popular service at St Stephen's. Women not previously using medical services are attending. The multidisciplinary nature of the clinic encourages a wider use of medical and paramedical services. Attendance record for HIV positive women has improved significantly. Whether these factors will lead to improved standards of sexual health will require a longer period of audit. Seventy-nine per cent of women indicated they would use a family planning service if available. An integrated family planning clinic was introduced after the audit period.