| Literature DB >> 28093686 |
Jennifer A Hall1, Lorna Benton2, Andrew Copas3, Judith Stephenson4.
Abstract
Introduction Previous systematic reviews concluded that rigorous research on the relationships between pregnancy intentions and pregnancy outcomes is limited. They further noted that most studies were conducted in high-income countries and had methodological limitations. We aim to assess the current evidence base for the relationship between pregnancy intention and miscarriage, stillbirth, low birthweight (LBW) and neonatal mortality. In March 2015 Embase, PubMed, Scopus and PsychInfo were searched for studies investigating the relationship between pregnancy intention and the outcomes of interest. Methods Studies published since 1975 and in English, French or Spanish were included. Two reviewers screened titles and abstracts, read the full text of identified articles and extracted data. Meta-analyses were conducted where possible. Results Thirty-seven studies assessing the relationships between pregnancy intention and LBW were identified. A meta-analysis of 17 of these studies found that unintended pregnancies are associated with 1.41 times greater odds of having a LBW baby (95%CI 1.31, 1.51). Eight studies looking at miscarriage, stillbirth or neonatal death were found. The limited data concerning pregnancy loss and neonatal mortality precluded meta-analysis but suggest these outcomes may be more common in unintended pregnancies. Discussion While there seems to be an increased risk of adverse pregnancy outcome in unintended pregnancies, there has been little improvement in either the quantity of evidence from low-income countries or in the quality of evidence generally. Longitudinal studies of pregnancy intention and pregnancy outcome, where pregnancy intention is assessed prospectively with a validated measure and where analyses include confounding or mediating factors, are required in both high- and low-income countries.Entities:
Keywords: Low birthweight; Meta-analysis; Miscarriage; Neonatal mortality; Pregnancy intention; Stillbirth; Systematic review
Mesh:
Year: 2017 PMID: 28093686 PMCID: PMC5357274 DOI: 10.1007/s10995-016-2237-0
Source DB: PubMed Journal: Matern Child Health J ISSN: 1092-7875
Fig. 1Flow chart of selection of studies for the literature review
Characteristics of studies investigating the relationships between pregnancy intention and miscarriage, stillbirth or neonatal mortality
| First author, year, location | Study population (size) | Methodology | Measure of intention and timing of assessment | Proportion of UIPs | Result for miscarriage | Result for still-birth | Result for neonatal death | Result for post-neonatal mortality | Result for infant mortality | Result for child mortality | Limitations/comments |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Dawen et al. ( | Women presenting to an early pregnancy unit in London over 3 years (4139) | Retrospective observational cohort study of pregnant women who had documentation of outcome and whether the pregnancy was planned or unplanned | Question not included. Antenatal | 35.9% | No difference (40.5% versus 42.5%) | Limited information as only an abstract, no raw data so can’t calculate OR; not even clear which way round the percentages are | |||||
| Wellings et al. ( | A nationally representative sample of 15 162 men and women aged 16–74 years, looked at women aged 15–44 who had a pregnancy in the last year (5686) | Cross-sectional survey | London Measure of Unplanned Pregnancy. <12 months postnatally | 16.2% unplanned 29% ambivalent | No significant difference on univariate analysis (unplanned 33.6%, planned 35.3%) | Used LMUP but dichotomised and did so at unusual cut-point. Retrospective, cross-sectional data. No adjusted analysis presented | |||||
| Singh and Mahapatra ( | Currently married women aged in 15–39 in four states in 2002–03 who had been interviewed in the National Family Health Survey in 1998–99 were re-interviewed (2108) | Surveys completed at the two time points and asking about the time in between | Fertility intentions in non-pregnant women: Would you like to have (a/nother) child or would you prefer not to have any more children? How long would you like to wait from now before the birth of (a/nother) child? For pregnant women: DHS question. Pre-conception | 49.0% | Adjusted OR 1.83 (1.01, 3.34) | aOR 1.52 (0.95, 2.45) | Only currently married women, limited age range. Asked about future fertility intentions and used this to assign wantedness to future pregnancies, without recognising that this could have changed. Excluded women who were ‘unsure’. Pregnancies that did not result in a live birth were not included | ||||
| Assefa et al. ( | Women who became pregnant in one of 12 kebeles during the study period | Women visited every 3 months and tested for pregnancy, then visited monthly to determine pregnancy outcome | Question not included. Antenatal | 31.8% | Crude HR 3.0 (2.15, 4.15), adjusted HR 2.2 (1.56, 3.11) | Will have missed some early miscarriages, but this should be minimal. Can’t differentiate between miscarriage, abortion and stillbirth so all combined into pregnancy loss | |||||
| Singh et al. ( | A nationally representative sample of 124 385 women aged 15–49 (51,555) | Cross-sectional survey | DHS question, <12 months postnatally | 20.3% | aOR mistimed 1.82 (1.16, 2.84), aOR unwanted 2.22 (1.17, 4.24) | aOR mistimed 2.60 (1.07, 6.76), aOR unwanted 3.64 (1.39, 9.51) | aOR mistimed 1.37 (0.48, 3.89), aOR unwanted 5.92 (1.48, 23.7) | Retrospective DHS style questions, up to 5 years after the birth. Only live births included. ‘Child’ mortality actually 12–35 months | |||
| Chalasani et al. ( | Women in the Sample Registration System in the Jessore and Sirajgonj districts (3283) | Baseline and quarterly surveillance from 1982 to 2002 | Women were asked prospective preferences about how many further children they wanted of each sex; subsequent births were then categorised as wanted, “up to God”, and unwanted. Pre-conception | 41.0% | Adjusted OR 2.09 (p < 0.001) | Adjusted OR 2.00 (p < 0.001) | Deaths from 12 to 60 months. Adjusted OR 1.38 | ||||
| Bustan and coker ( | Pregnancies in women who were members of the Kaiser Health Plan in the East Bay Area of San Francisco (20,754) | Women recruited on confirmation of pregnancy, interviewed and data extracted from medical records | Wording of question not included but asked about the attitude of the woman and her partner to the pregnancy. Antenatal | 14.4% | Crude RR 1.4 (1.0, 1.8), adjusted RR 1.1 (0.9,1.5) | Crude RR 2.7 (1.8, 4.3), adjusted RR 2.4 (1.5, 4.0) | Crude RR 0.8 (0.4, 1.9), adjusted RR 0.9 (0.5,1.9) | Excluded unmarried women and those who said that their attitude to the pregnancy was different to their husbands. Also women who had access to this health care plan—suggests low-risk population raising issues of representativeness | |||
| Laukaran and Van Den Berg ( | Women enrolled in the child health and development studies who were a member of the Kaiser Foundation Health Plan in the San Francisco East Bay Area (12391) | Utilises data from the Child Health and Development studies. Ever-married women receiving antenatal care at KFH. Outcome data from medical records | How do you feel about having a baby now?’ Antenatal | 6.2% strong negative attitude | The relative risk (RR) adjusted for parity and husband’s occupation was 1.80 (p = 0.003) and adjusted for mother’s age and parity was 1.78 (p = 0.002) | Prospective study but measure of intention not comparable. Analysis only conducted on ever-married white women and only controlled for a couple of confounders | |||||
Adjusted odds ratios and 95%CI for pregnancy intention and neonatal mortality
| Study | Neonatal mortality | Post-neonatal mortality | Deaths from 12 to 35 months |
|---|---|---|---|
| Singh et al. ( | |||
| Mistimed births | 1.82 (1.16, 2.84) | 2.06 (1.07, 6.76) | 1.37 (0.48, 3.89) |
| Unwanted births | 2.22 (1.17, 4.24) | 3.64 (1.39, 9.51) | 5.92 (1.48, 23.7) |
| Chalasani et al. ( | |||
| Unwanted births | 2.09 (p < 0.001) | 2.00 (p < 0.001) | – |
Characteristics of studies investigating the relationships between pregnancy intention and low birthweight
| Author, year, location | Study population (size) | Methodology | Measure of intention and timing of assessment | Proportion of UIPs | Measure of birth weight | Confounders controlled for | Result for LBW, unadjusted | Result for LBW, adjusted | Limitations/comments | In meta-analysis |
|---|---|---|---|---|---|---|---|---|---|---|
| Kost and Lindberg ( | Non-multiple live births in 3 years preceding the interview (4184) | Analysis of pooled NSFG data from 2 survey rounds | NSFG question plus How much later did you want to become pregnant? And a multi-dimensional measure assessing trying, wanting and happiness. Postnatal mixed | 30% | LBW <2500 | Age, SES, marital status, education, parity, ethnicity, health insurance | 6% intended, 12% UIP, p < 0.05 | Not able to calculate /compare results presented | Retrospective, recall, live births only, but large, representative survey. Strong analytic methodology | Yes |
| Wado et al. ( | Community-based cohort of pregnant women in 11 kebeles in south-western Ethiopia (537) | Interview during pregnancy with follow up within 72 h to of birth to weigh the baby | DHS question. Plus questions about happiness with pregnancy. Antenatal | 41% | LBW <2500 | Age, education, SES, MUAC, AND, social support | OR 2.31 (1.25, 4.27) | RR 1.25 (0.73, 2.14) for mistimed, RR 2.08 (1.02, 4.23) for unwanted | Excluded stillbirths and neonatal deaths | Yes |
| Lindberg et al. ( | Women who delivered live births in Oklahoma between 2004 and 8 and completed a follow-up survey in 2006–10 (8327) | Analysis of PRAMS data (self-administered cross-sectional survey) for Oklahoma linked to 2 years follow up survey | PRAMS question plus How much later did you want to become pregnant? Postnatal 1–6 months | 49% | LBW <2500 | Age, SES, marital status, education, parity, ethnicity, smoking/alcohol, health insurance | 8% in UIP, 7% in IP, p < 0.05 | OR 1.19 (0.93, 1.53) unwanted, 0.85 (0.70, 1.02) for mistimed > 2years, 0.95 (0.80, 1.12) mistimed < 2 years | Retrospective, recall, live births only, but large, representative survey | Yes |
| Kayode et al. ( | Women in 2003/2008 DHS who had given birth (5013) | Analysis of DHS data | DHS questions. Postnatal mixed | 30.6% | LBW <2500 | None | 18% in UIP, 16% in IP, no sig test | – | DHS style questions and methods, analysis is focused on LBW so no data on confounding of UIP | Yes |
| Saedi et al. ( | Unclear | Unclear | Unclear | 28% | LBW <2500 | Not clear | 8.5% in unwanted, 11% in wanted, not sig | – | Too little information on methodology, poor quality | No |
| McCrory and McNally ( | Children aged 9 months between Sept 2008-April 2009 (11,134) | Weighted sample from Child Benefit Register, 64.5% response rate, about 25% of all births. Families interviewed in person and CASI at 9 months | Wording not clear but ‘asked the mother whether she intended to become pregnant before the study child was conceived’. Postnatal 7–12 months | 41% | LBW <2500 | Age, SES, marital status, education, parity, ethnicity, smoking, ANC | OR 1.11 (0.94, 1.31) | RR 1.01 (0.83, 1.22) | Retrospective, recall, live births only, but large, nationally representative survey. Mixed up categories of intention | Yes |
| Flower et al. ( | Singleton babies born in UK in 2000–01 (18,178) | Analysis of Millennium Cohort Study data | Were you planning to get pregnant or was it a surprise? Postnatal 7–12 months | 43% | LBW <2500 | Age, SES, marital status | 5.2% in planned, 7.2% in UIP | OR 1.24 (1.04, 1.48) | Adjusted 1.24. Retrospective, recall, live births and singletons only, but large, nationally representative survey | Yes |
| Flores et al. ( | Utah women delivering single live birth >20 weeks gestation (190,948) | Analysis of PRAMS data for Utah, linked to birth certificates | PRAMS question. Postnatal 1–6 months | 39% | LBW <2500 | None | In some ethnic groups, women with UIP were significantly more likely to have a LBW | – | Abstract only so can’t make a thorough assessment but using PRAMS data, which from other papers appears to be good. Most comparisons are between different ethnicities | No |
| Postlethwaite et al. ( | Women insured with Kaiser Permanante (1671) | Retrospective medical record review of women receiving their first ANC visit at one of the KP obstetric offices in 2002, random sample of 400 taken from each clinic, 2400 records reviewed | At the time that you conceived, did you want to become pregnant (intended vs. unintended), did you want to become pregnant but not at this time (mistimed), or did you not want to become pregnant at all (unwanted)? Antenatal | 37.8% | SFGA | None | 4.8% unwanted, 2.3% intended, says not sig | – | All women had a KP pre-paid health plan and access to ANC. They had earlier initiation of ANC than nationally (88–89% v 84%), lower levels on UIP (37.8% v 49% p < 0.0001) and low levels of SFGA (3.37%)—suggests that this is an advantaged population. SFGA only, data not comparable | No |
| Iranfar et al. ( | Women on the postnatal ward at Kermanshah maternity hospital (114) | Case-control study on postnatal ward | Questions on birth control method and stopping time, planning for pregnancy and tendency to abortion. Postnatal <1 month | 47% | BW <3000 g and average birthweight | None | 35.7% in UIP, 27% in IP, p = 0.51 | – | Cases should have been those with low birthweight, not those with UIP. Measure of intention not clear - seems to be that it was assumed to be UIP if the woman had been using contraception. Presents <3000 g so not comparable data | No |
| Hohmann-Marriott ( | Participants of the Early Childhood Longitudinal Study (ECLS) birth cohort where biological father resident at 9 months (5788) | Analysis of couple level data from interviews at 9 months in the ECLS on conception, pregnancy and birth, linked with birth certificate data | At the time that you/your partner became pregnant with your baby, did you yourself actually want to have a(nother) baby at some time? Did you/your partner become pregnant sooner than you wanted, later than you wanted to at about the right time? Postnatal 7–12 months | Can’t do | LBW <2500 | OR 1.36, no 95%CI given, says not sig | No data | Inclusion criteria of father resident at 9 months will bias the results to the null because fathers of UIPs are less likely to be living with the child at 9 months than fathers of IP. Data presented on couple intentions is incorrect. Can’t extract numbers to calculate ORs. Presented OR is mother only - not comparable - would need TO be combination of mother only and both v father only and neither but data not available | No | |
| Shaheen et al. ( | Ever married women in the Demographic and Health Survey (DHS) (2379) | Analysis of DHS data | DHS question. Postnatal 7–12 months | 18% | Women’s assessment of size | Age Parity | UIP more likely to report smaller than average size OR 1.34 (1.02, 1.76) | – | Outcome assessed by women’s report of size - subjective. Only married women and only live births therefore underestimates UIP rate | No |
| Mohllajee et al. ( | Women who gave birth in 18 states in 1996–99, multiple births excluded (87,087) | Analysis of PRAMS data for 18 states linked to birth certificates | PRAMS questions. Postnatal 1–6 months | 47% | LBW <2500 and LBW <10% | Age Parity Marital status Education Smoking / alcohol ANC Previous LBW / PTB | 6.8% UIP, 5% IP, p < 0.01 | OR 1.06 (0.97, 1.16) unwanted, OR 0.92 (0.86, 0.97) mistimed, OR 1.15 (1.02, 1.29) ambivalent | Retrospective, recall, live births only | Yes |
| Collier and Hogue ( | Women who gave birth in Georgia in 1996–97 (211,716) | Analysis of PRAMS data for Georgia linked to birth certificates | PRAMS questions. Postnatal 1–6 months | 63% | LBW <2500 | None | RR 1.37 (1.08, 1.72) | – | Retrospective, recall, live births only | Yes |
| Rafati et al. ( | Births in two hospitals in Tehran (460) | Case-control study on postnatal ward—cases = LBW, controls = 2 babies >2500 g born consecutively after each case. Neonates with complications excluded | Unclear. Postnatal <1 month | 3% | LBW <2500 and average birthweight | None | In LBW babies 6% were UIP, in normal birthweight 1% were UIP, p < 0.001 | – | Measure of intention not described | No |
| D’Angelo et al. ( | 15 states (25,027) | Analysis of PRAMS data for 15 states linked to birth certificates | PRAMS questions. Postnatal 1–6 months | 43% | LBW <2500 | None | 9.6% in unwanted, 6.5% in wanted, p < 0.001 | – | Retrospective, recall, live births only | Yes |
| Durousseau and Chavez ( | California, term births to >15 yo during February to May 1999 and from February to May 2000 Inc. twins and triplets (5941) | Uses California’s Maternal Infant Health Assessment (MIHA) an annual population-based self-administered mail survey with telephone follow up for non-responders that collects information about pregnancy-related conditions and behaviours | Question about whether before pregnancy the mother wanted to get pregnant then, later, or not at all or was unsure, respectively plus her initial happiness about becoming pregnant on a five point Likert scale of: very happy; somewhat happy; somewhat unhappy; very unhappy; and unsure. Postnatal 1–6 months | 47% | SFGA | Age Education Ethnicity Smoking Previous LBW / PTB | OR 1.2 (0.6, 2.3) | No data but says non-significant relationship | Retrospective, recall, live births only. Sample only includes over 15, English and Spanish speaking women. Only those giving birth in Feb-May each year | No |
| Pulley et al. ( | 1995 National Survey of Family Growth (NSFG) women with a single live birth in the last 5 years (4120) | Included all pregnancies reported in the 1995 NSFG ending in a live birth in the 5 years prior to the woman’s interview. The 1995 version of the intendedness questions was used and all women were asked how happy they were when they learned they were pregnant | NSFG question: plus a 10-point scale measuring happiness about a pregnancy. Postnatal mixed | 31% | LBW <2500 | Marital status Age Education Parity SEC Ethnicity | 6% unwanted, 5.1% intended, says not sig | – | Retrospective, recall, live births only | Yes |
| Korenman et al. ( | Women in the National Longitudinal Survey of Youth (NLSY) who had at least one birth after 1978 (7800) | Uses data from the 1979–92 NLSY from women who had at least one birth after 1978 | Four questions about pregnancy intention described as similar to those in the NSFG but not specified. Postnatal mixed | 37% | LBW <2500 | None | 10.4% mother only intended, 7% if both intended | No data | Mostly focused on comparisons of intention between the partners. Uses models that attempt to account for uncontrolled confounding factors through within family comparisons on intended and unintended births | Yes |
| Ahluwalia et al. ( | 13 states women with singleton births (15,219) | Analysis of PRAMS data for 13 states linked to birth certificates | PRAMS questions. Postnatal 1–6 months | 45% | SFGA | None | OR 1.25 (0.99, 1.58) | – | Retrospective, recall, live births only. SFGA data only, not comparable | No |
| Eggleston et al. ( | DHS (2490) | Subsample of the DHS | DHS questions. Postnatal >12 months | Women’s assessment of size and LBW <2500 | ANC Smoking Alcohol consumption Age Parity rural v urban Education | OR 1.64 (1.22, 2.20) | Unwanted OR 1.64 (1.22, 2.20), mistimed OR1.18 (0.88, 1.60) | Uses mother’s assessment of size for outcome, as well as numeric answer if that was available. Had to exclude a large number of women who did not report their infant’s weight - these women may be more likely to have characteristics associated with LBW and therefore would lead to an underestimate | No | |
| Joyce et al. ( | Women in cohort giving birth between 1979 and 1992 (7751) | National Longitudinal Survey of Labor Market Experience, a probability sample of young adults between the ages of 14 and 21 in 1979, the first year of the survey. Respondents are interviewed annually. Have sibling data so can compare intendedness within families | Four questions about pregnancy intention described as similar to those in the NSFG but not specified. Postnatal mixed | 44% | LBW <2500 | None | 11.6% in unwanted, 6.4% in intended, no sig test | Only effect sizes presented so not able to compare | Multiple models with different control groups and confounders. Uses mother’s report of birthweight, says that there are high rates of agreement between this and vital records | Yes |
| Sable and Wilkinson ( | Missouri live singleton births between Dec 1 1989 and Mar 31 1991 (2378) | National Institute of Child Health and Human Development / Missouri Maternal and Infant Health Survey, a population based case control study. Cases were vLBW, matched with 2 controls next births—one LBW and one NBW, identified from birth certificate data | NSFG questions. Postnatal mixed | 57.9% | LBW <2500 and vLBW | None | 0R 0.90 (0.74, 1.10) for moderately LBW (1500–2499) v normal | – | Mixed methods of data collection and variable time to data collection. Retrospective, recall. Weights compared differently to other studies; vLBW v normal and moderate LBW v normal so not comparable | No |
| Colley et al. ( | Mothers who had a live-born infant in the 13 included states in 1997 | Analysis of PRAMS data for 18 states linked to birth certificates | PRAMS questions. Postnatal 1–6 months | 33–59% | LBW <2500 | None | No data but says no differences in LBW by intention | – | Methods robust but some repeated data from other PRAMS studies in the same states and same year. Also no data presented to enable a calculation | No |
| Fourn et al. ( | Women attending ANC in Cotonou hospital (4113) | Used a questionnaire at first ANC to gather socio-demographic data, obstetric history. Followed up through pregnancy and complications were recorded | Women were asked at the first visit if the pregnancy was wanted or unwanted. Antenatal | 17% | LBW <2500 | Pregnancy complications Age Parity | 13% unwanted in NBW, 21.7% unwanted in LBW | OR 1.6 (1.30, 2.00) | Only women attending ANC at the hospital, but they say that about 90% of the local population access this. Not entirely clear what is adjusted for in the analysis | Yes |
| Kost et al. ( | NMHIS women aged 15–49 in 48 states who had a live birth in 1988 or NSFG nationally representative sample of women aged 15–44 who gave birth 1984–88 (11,585) | Data from national maternal and infant health survey and the national survey of family growth, NMHIS postal questionnaire, women aged 15–49 in 48 states who had a live birth in 1988. NSFG interviews with nationally representative sample of women aged 15–44 who gave birth between 1984 and 1988, birth certificates | NSFG questions. Postnatal mixed | n/a | LBW <2500 and LBW <10% | None | LBW more common in unwanted (9.7%) and mistimed (6.5%) pregnancies than intended pregnancies (5.1%), p < 0.05 | - | Can’t calculate odds ratio as numeric data not presented. Lots of interesting data from the regression models. Importance of planning for early recognition of pregnancy and timely ANC | No |
| Mitchell and McCormack ( | Participants included women who had a live birth, a stillbirth, or an infant death in 1988 (18,000) | 1988 NMIHS data and presentation of other analyses of the 1982–88 NSFG data. The women completed a 40-minute mailed questionnaire regarding prenatal care, health habits, and pregnancy outcomes | NSFG questions. Postnatal mixed | 40% | LBW <2500 | None | 10.8% in unwanted, 6.7% in wanted, says sig | – | Retrospective, recall, live births only | Yes |
| Bitto et al. ( | All women in the study who became pregnant between Jan1987 and Sept 1990 in the 5 centres (656) | Sub-study of a multicentre international prospective cohort study of women using natural family planning methods designed to ascertain the effects of timing of conception on pregnancy outcome. Intention determined on recognition of pregnancy, followed up at 16 and 32 weeks and after delivery | Women asked at time pregnancy recognised whether the pregnancy had been planned. Validated by natural family planning instructor after talking to woman and reviewing her chart and independently reviewed. Defined as planned if women stated it was her intention to become pregnant and her chart showed intercourse during her fertile period. Antenatal | 51% | LBW <2500 and average birthweight | Age pregnancy complications BMI Smoking / alcohol Parity Previous LBW/PTB infant sex | OR 0.69 (0.30, 1.58) | OR 0.90 (0.24, 3.44) | Users of natural family planning - not representative of a wider population—Doesn’t present results by centre despite stating that they were very different—Chile had 37–40% unplanned pregnancies; DC had <2%—seems like very different populations, only have one OR for all data | No |
| Bustan and Coker ( | Pregnancies in women who were members of the Kaiser Health Plan in the East Bay Area of San Francisco (20,754) | Women recruited on confirmation of pregnancy, interviewed and data extracted from medical records | Wording of question not included but asked about the attitude of the woman and her partner to the pregnancy. Antenatal | 14.4% | LBW <2500 | None | Not presented and no raw data | OR 1.72 (1.08, 2.76) | Excluded unmarried women and those who said that their attitude to the pregnancy was different to their husbands. Excluded those with missing data on intention or who were not interviewed during pregnancy, and selected one pregnancy per women reduced the sample size to 8823 from over 20 000, also women who had access to this health care plan - suggests that these women were at less risk of UIP and of adverse outcomes raising issues of representativeness | No |
| Sharma et al. ( | High risk inner city women with a live birth between 1989 and 1991 in one of six geographical areas (1004) | Telephone interviews of 1004 women of childbearing ages (15 to 44 years), selected through random digit dialling procedure | Exact questions not presented but based on PRAMS and MIHS. Postnatal mixed | 54% | LBW <2500 | Age Marital status Education Ethnicity SEC maternal conditions Previous abortion | 1.1 (0.9–1.4) according to paper, no raw data given | – | Selected high-risk populations, excludes those without telephones who are likely to be more disadvantaged. Live births only. Don’t present data, only adjusted OR and it isn’t clear what was included in the model | No |
| Gadow et al. ( | 5155 normal women having normal offspring in 18 maternity hospitals participating in the ECLAMC in 1992–94 (5155) | As the control group of a south American study on malformations 5155 normal women having normal offspring were interviewed during the post-partum period in 18 maternity hospitals participating in the ECLAMC. This data is analysed here | (i) if this gestation was intended or not; and (ii) if contraceptive methods were used or not.. Postnatal <1 month | 50% | Average birthweight | Age Education Parity Ethnicity | No differences in average birthweight, but raw data nor presented | – | Multi-centre study with results presented as aggregate may mask differences at country level. Retrospective but closer to delivery. Only live births. Slightly difference measure of intention. Only presents average birthweight | No |
| Poland et al. ( | 200 poor, mainly black women who delivered at the Hutzel Hospital in Detroit over a 26 month period (200) | Interview and review of medical records | Initial attitude to pregnancy recorded as mixed, negative or positive. Time delay before telling second person about the pregnancy. Postnatal <1 month | 50% | LBW <2500 | None | Attitude to pregnancy contributes to variation in prenatal care which contributes to 26% of the variation in birthweight | – | Develops a model to assess the contribution of different factors to LBW. Doesn’t quantify difference in LBW between intention groups. Intention not robustly assessed and not comparable to others | No |
| Cartwright ( | Random sample of women with live births that year in 10 areas in England (1486) | Sub-study of a methodological study to assess the feasibility of monitoring maternity services through postal questionnaires. Random sample of births in each area (areas chosen systematically with a random starting point and with probability proportional to the number of births in 1982) in 1 month in 1984. Postal questionnaires sent about 4 months after birth with up to two reminders | ‘When you first found you were pregnant, how did you feel about it then? Would you rather it had happened a bit later or were you pleased you were pregnant then, or sorry it had happened at all?’ ‘Around the time you became pregnant were you or your husband or partner generally using any method of birth control? ‘So would you say you intended to become pregnant or not? Stated intentions used in the analysis. Postnatal 1–6 months | 27% | LBW <2500 | None | Decreasing proportion of unintended pregnancies as birthweight increases | – | Retrospective, live births but comment on all conceptions. Measure of intention not standardised but similar to others | Yes |
| Marsiglio and Mott ( | 6015 women in the NLSY who were interviewed in 1984 and who had had one child (1581) | Uses data from the 1979–92 National Longitudinal Survey of Youth (NLSY) from women who had at least one birth after 1978 | ‘Was the reason you (were not/stopped) using any contraceptive methods because you yourself wanted to become pregnant?’ Those who answered ‘no’ were then asked, ‘Just before you became pregnant did you want to become pregnant when you did?’ if ‘no’, ‘Did you want a baby but not at that time, or did you want none at all?’. Postnatal mixed | 45% | LBW <2500 | Age Ethnicity | 7.9% in unwanted, 6.1% in wanted, says not sig | Can’t calculate but says not significant | Looking at direct and indirect relationships between intention and LBW through antenatal behaviours. Does multivariate regression | Yes |
| Pamuk and Mosher ( | Women aged 15–44 in the USA 7969 | Data from the NFSG 1982 survey. Personal interviews were conducted with a multistage area probability sample of 7969 women 15–44 years of age | NSFG questions. Postnatal mixed | 40% | LBW <2500 | None | No data but says no differences noted in LBW by intention | – | Retrospective, live births only | No |
| McCormick et al. ( | Low income women in central Harlem (458) | Women attending for ANC at Harlem Hospital and affiliated clinics completed a questionnaire covering socio-demographics, attitude to child, health behaviours and exposure to stressful events | A series of questions on attitude to the pregnancy including ‘Did you plan this pregnancy?’ and whether they were surprised at being pregnant. Antenatal | 73% | LBW <2500 | None | No data but says no differences were noted in LBW by intention | – | No data presented so can’t calculate, says no relationship between planning and LBW / PTB. A group of low-income urban women, not many differences between planned and unplanned on socio-demographic characteristics or behaviours therefore no differences in outcomes not so surprising. Only presents data on women who attended for ANC | No |
| Laukaran and Van Den Berg ( | Ever married women who were a member of the Kaiser Foundation Health Plan in the San Francisco (12,391) | Data from the Child Health and Development studies, a prospective analysis of maternal attitude in relationship to events during pregnancy and delivery and pregnancy outcomes. Outcomes from medical records | How do you feel about having a baby now?’ 7 options divided into 4 categories of attitude and then pregnancy divided into wanted if there was a strong favourable response and unwanted if there was a negative response; Antenatal | 28.20% | LBW <2500 | None | No data but says no differences were noted in LBW by intention | – | Prospective study but measure of intention not comparable, only compares two extremes and middle section ignored. No data presented so can’t calculate - just says that no relationship between attitude and LBW | No |
| Morris et al. ( | Random selection of women giving birth in one of the hospitals included in the Family Planning evaluation (7921) | Interview on the postnatal ward of a random selection of women with live births in 60 hospitals in 17 major cities | Just before you became pregnant this time, did you: (1) want to become pregnant, (2) want a(nother) baby, but didn’t want to become pregnant yet, or (3) not want a(nother) baby? (Go to Q. 9b) (4) didn’t matter. 9b. At the time you became pregnant, did you feel (1) you would want a(nother) baby some time later (2) you would never want a(nother) baby?. Postnatal <1 month | 22.1% in blacks, 10.9% in whites | LBW <2500 | Stratified analyses by education, parity, marital status | 6.6% in unwanted, 4.3% in wanted in whites (p < 0.05), 10.1% in unwanted, 9% unwanted in blacks, not sig | – | Retrospective, but very near to birth so less potential for recall bias, live births only | Yes |
Fig. 2Flow chart of the studies in the pregnancy intention and LBW meta-analysis
Fig. 3Forest plot of the random effects meta-analysis of studies assessing the relationship between pregnancy intention and LBW
Fig. 4Forest plot of the random effects meta-analysis of studies assessing the relationship between pregnancy intention and LBW stratified by location
Fig. 5Forest plot of the random effects meta-analysis of studies assessing the relationship between pregnancy intention and LBW stratified by timing of assessment of intention
Fig. 6Funnel plot for pregnancy intention and LBW
| Miscarriage | A pregnancy lost before 28 weeks’ gestation |
| Stillbirth | A baby born with no signs of life at or after 28 weeks’ gestation |
| Low birthweight | A baby born weighing <2500 g regardless of gestation |
| Neonatal death | A baby born alive but who dies within the first 28 days of life |
Wording of questions to assess pregnancy intention
| Survey name | Pregnancy intention questions on survey |
|---|---|
| National Survey of Family Growth (NSFG) from 1973, 1976, 1982, 1988, 1995, 2002, 2006–10 and 2011–13. USA | 1. Was the reason you (were not/stopped) using any method because you, yourself, wanted to become pregnant? (Yes/No - If yes, go to Q4, If no, go to Q2) |
| Pregnancy Risk Assessment Monitoring System (PRAMS) from 1987 to date. USA | 1. Thinking back to just before you were pregnant, how did you feel about becoming pregnant? |
| Demographic and Health Survey | At the time you became pregnant did you want to become pregnant then, did you want to wait until later, or did you want to have no (more) children at all? |