Is Unintended Pregnancy Associated with Increased Blood

Pressure during Pregnancy?

Author Author AuthorDate

PH 251A

Our Question

Is there an association between unintended pregnancy and gestational hypertension among a sample of pregnant women living in Oakland, CA from 1959-1966?

The stress of an unintended pregnancy will increase maternal blood pressure beyond the natural changes associated with pregnancy.    

Hypothesis

Why is this important to look at?

• 6-8% of pregnant women experience hypertension

– Increased risk of pregnancy complications

– Risk of preterm delivery

– Maternal and child morbidity and mortality

• 50% of pregnancies are unintended

• No established literature linking the two

Previous Research Studies

• Conflicting research on the relationship of stress and hypertension in pregnancy– Anxiety and depression no association (Vollebregt et al., 2008)

– Anxiety and depression preeclampsia (Kurki et al., 2000)

– Job strain preeclampsia (Klonoff, 1996 and Marcoux, 1999)

• Unintended pregnancy higher risk for stress (OR: 3.4) and depressive symptoms (OR: 3.1) (Messer et al, 2005)

• No studies on pregnancy intention and maternal health outcomes

Study Sample

• Child Health and Development Studies (CHDS)• Kaiser Health Plan, Oakland, CA • June 1959 - September 1966

Study sample

All CHDS pregnanciesN=20,754

Singleton, live birthsN=19,229

Married womenN=13,467

No pre-existing hypertension

N=8,273

Has exposure and outcome variables

N=6,402

Exposure: Intendedness

Intended38%

Unintended62%

“Did gravida decide in advance to have baby?”

Hyper-tensive16%

Not hyper-tensive84%

Outcome: Blood PressureAt least one hypertensive measurement

(>140 systolic or >90 diastolic) over the course of a pregnancy

International Society for the Study of Hypertension in Pregnancy, Vollebregt, KC 2007

Our Population

15-19 20-24 25-29 30-34 >340%

10%

20%

30%

40%

50%

Gravida Age

High27%

Upper-Middle

12%Middle

10%

Lower-Middle

35%

Low15%

SES Distribution

Covariates

• Age• Race• SES• Maternal education• Pre-pregnancy employment• Parity• BMI• Previous Oral Contraceptive Use• Prenatal Care• Smoking• Alcohol Consumption• Coffee Consumption

Covariates associated with pregnancy intention

• Age**• Race**• SES**• Maternal education**• Pre-pregnancy employment**• Parity**• BMI**• Previous Oral Contraceptive Use**• Prenatal Care**• Smoking*• Alcohol Consumption**• Coffee Consumption

*p<0.05**p<.01

Covariates associated with gestational hypertension

• Age• Race**• SES• Maternal education• Pre-pregnancy employment**• Parity**• BMI**• Previous Oral Contraceptive Use*• Prenatal Care**• Smoking• Alcohol Consumption• Coffee Consumption

*p<0.05**p<.01

Covariates associated with both

• Age• Race• SES• Maternal education• Pre-pregnancy employment• Parity• BMI• Previous Oral Contraceptive Use• Prenatal Care• Smoking• Alcohol Consumption• Coffee Consumption

Data Analysis

• Logistic Regression

• Testing for interaction– Intendedness*age– Intendedness*SES– Intendedness*parity

• Evidence of confounding determined by change in estimate by 10% or p-value <.10

Our final model

• Intendedness• Age• Race• SES• Parity• BMI• Previous Oral Contraceptive Use• Prenatal Care• Indendedness*SES

Results- Main effect model

• No association with pregnancy intention and gestational hypertension.

• Women older than 34 had 1.6 times the odds of developing gestational hypertension compared to women under the age of 19. (CI:1.1, 2.4)

• Women classified as "other" for their race had an OR of 0.5 (0.4, 0.7) compared to white women, indicating a protective association from gestational hypertension.

• Being multiparious compared to primiparious was protective. OR=0.5 (0.5, 0.6)

Results- Main effect model

• Women with a BMI over 25 had 2.3 times the odds of developing gestational hypertension compared to women with BMI equal to or less than 25. (CI: 2.0, 2.7)

• Women who previously used oral contraceptive had 1.4 times the odds of developing gestational hypertension than women who did not use oral contraceptives. (CI: 1.0, 1.8)

• Women with less than 8 prenatal care visits had a protective association compared to women with more than 8 visits. OR=0.5 (0.4, 0.6)

Results - Interaction

• Among women in the middle class, women with unintended pregnancies have 1.9 times the risk of developing gestational hypertension than women with intended pregnancies. (CI: 1.1, 3.3)

• Among women in lower middle class, women with unintended pregnancies have 1.9 times the risk of developing gestational hypertension than women with intended pregnancies. (CI: 1.2, 3.1)

In summary

In our sample, there is no association between unintended pregnancies and gestational hypertension EXCEPT in the lower middle and middle class women.

Discussion

The following findings confirm what we have seen in the literature:

• Women with a BMI over 25: OR=2.3 (2.0, 2.7)• Women older than 34: OR= 1.6 (1.1, 2.4)• Multiparous women: OR=0.5 (0.5, 0.6)

Strengths

– Data at multiple-time points• Prepregnancy blood pressure readings

– Intendedness variable: yes/no–Most unintended pregnancies carried to term

Limitations

–Can’t control for all confounders: i.e. family history, autoimmune disorders–Differences in prenatal visit patterns–Different social context

*Time Frame of study both strength and limitation*

Future Directions

• Further research could be conducted using all blood pressure measurements available to assess if trends are present

• Does the relationship between unintendedness and gestational hypertension exist in lower-middle and middle class women today? – Do these women have proper access to birth control?

Our Population

White73%

Black17%

Other10%

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