|Year : 2018 | Volume
| Issue : 4 | Page : 234-238
Foeto-placental parameters in normal pregnancy and factors affecting them
Ochuwa Adiketu Babah1, Ayodeji A Oluwole1, Opeyemi R Akinajo2, Emmanuel Owie2, Ephraim O Ohazurike2
1 Department of Obstetrics and Gynaecology, Faculty of Clinical Sciences, College of Medicine, University of Lagos/Lagos University Teaching Hospital; Department of Obstetrics and Gynaecology, Lagos University Teaching Hospital, Lagos, Nigeria
2 Department of Obstetrics and Gynaecology, Lagos University Teaching Hospital, Lagos, Nigeria
|Date of Web Publication||21-Dec-2018|
Dr. Ochuwa Adiketu Babah
Department of Obstetrics and Gynaecology, Faculty of Clinical Sciences, College of Medicine, University of Lagos/Lagos University Teaching Hospital, Lagos
Source of Support: None, Conflict of Interest: None
Objective: The aim of this study was to evaluate foeto-placental (F/P) parameters, namely foetal birth weight, placental weight (PW) and F/P weight ratio, in normal pregnancy and factors affecting them. Methodology: A retrospective study was conducted on labour ward data obtained over a period of 3 years (2015–2017). Only deliveries above 28-week gestational age which met other selection criteria were included in the study. Their sociodemographic parameters, PW, foetal birth weight, foetal outcome and Apgar scores were extracted from the delivery registers. The F/P weight ratio was calculated from the values obtained. All data collected were subjected to statistical analysis using SPSS version 20. Results: The mean age ± standard error of mean of parturient was 31.84 ± 0.18 years. A larger proportion, 1455 (80.7%) of the women were booked. The mean gestational age ± standard deviation at delivery was 37.81 ± 2.72 weeks. Foetal weight (FW), PW and F/P weight ratio rise progressively with advancing gestational age in normal pregnancy, the FW rising faster than the placenta which gains weight slowly. The F/P ratio rises steadily initially and then abruptly from 42-week gestational age as the foetus outgrows the placenta, after which there is a sharp decline from 43-week gestational age. FW, PW and F/P ratio are significantly affected by gestational age and booking status (P = 0.000). Parity and foetal sex were found to have significant influence on FW alone (P = 0.026 and P = 0.000, respectively). Conclusion: This study clarifies the need to avoid undue prolongation of pregnancy beyond 42 weeks to avert adverse consequences which may be related to the differential growth in the foetus and placenta.
Keywords: Foetal birth weight, foetal outcome, foeto-placental weight ratio, normogram, placental weight
|How to cite this article:|
Babah OA, Oluwole AA, Akinajo OR, Owie E, Ohazurike EO. Foeto-placental parameters in normal pregnancy and factors affecting them. Niger Postgrad Med J 2018;25:234-8
|How to cite this URL:|
Babah OA, Oluwole AA, Akinajo OR, Owie E, Ohazurike EO. Foeto-placental parameters in normal pregnancy and factors affecting them. Niger Postgrad Med J [serial online] 2018 [cited 2021 Feb 25];25:234-8. Available from: https://www.npmj.org/text.asp?2018/25/4/234/248214
| Introduction|| |
The placenta, a new organ formed in the uterus during pregnancy, serves as an intermediary between the foetus and the mother. It is a vital organ for maintaining and continuing the healthy pregnancy and it aids gaseous exchange between mother and baby and facilitates the provision of nutrients to the developing foetus. It thus plays a key role in enhancing normal growth and development of the foetus. Therefore, anything that can alter or affect its development and function can cause a deleterious effect on the foetus and its ability to cope with the intrauterine environment.
At term, the placenta has been recorded to be on the average size of 185 mm in diameter, 23 mm in thickness, volume of 497 ml and a weight of 508 g accounting for the average ratio between placenta weight and newborn weight at term to be 1:6. These measurements, however, differ between different countries with different placental preparations. After delivery, precise and accurate examination of the placenta has been shown to provide an insight into the adaptation of the foetus to its environment.
A lot of factors have been shown to affect normal placenta growth. A major factor is maternal malnutrition which can result in failure of the developing foetus to thrive appropriately resulting in intrauterine growth restriction or intrauterine foetal death if severe. Other factors include environmental stressors, chronic infections, chronic anaemia and cardiovascular problems such as hypertension, metabolic disorders such as diabetes mellitus and congenital foetal anomalies which may be chromosomal or structural.
Various foeto-placental (F/P) parameters may be used in assessing foetal well-being and for prognostication of short- and long-term foetal outcomes. It is thus important for us to have a very good understanding of the pattern of these F/P indices in pregnancy. The oldest and commonly used parameter is foetal weight (FW), which can be estimated antenatally using ultrasonography, and the baby can easily be weighed at birth. Others are placental weight (PW) which can now be accurately predicted antenatally by measuring placental volume using ultrasonography and F/P weight ratio which can be calculated from the values for FW and PW.
The two standard references endorsed by the College of American Pathologists are absolute PW and F/P weight ratio. A close association has been noted between PW, birth weight (FW) and their ratio F/P in a number of studies., This has been used as an index signifying placental nutrient efficiency and has been linked with various unfavourable perinatal outcomes, such as non-reassuring foetal status, low Apgar scores and perinatal death. Till date, only FW is commonly used in our environment. Studies on PW and F/P are lacking in our environment. This study, therefore, aimed at evaluating F/P parameters, namely, foetal birth weight (FW), PW and F/P weight ratio (F/P) in normal pregnancy and factors affecting them.
The objectives of this study were:
- To assess the association between gestational age and mean FW, PW and F/P ratio in normal pregnancy
- To determine factors that may influence FW, PW and F/P ratio in normal pregnancy such as age, parity, booking status, gestational age and foetal sex
- To develop sex-specific normogram for F/P ratio in normal pregnancy.
| Methodology|| |
This was a retrospective cross-sectional study.
This study was conducted at the Lagos University Teaching Hospital, the largest tertiary health institution in Lagos state, Nigeria.
All deliveries conducted at the hospital's labour ward facility between 2015 and 2017, either booked or unbooked that meet the selection criteria.
Selection of cases and controls
All deliveries at gestational ages of 28 weeks and above were conducted at the hospital's labour ward facility and recorded in the delivery register. Those excluded from the study included those below 28-week gestational age, those with multiple gestations, congenital foetal anomaly and chronic medical conditions in pregnancy.
Information was collected from the labour ward register. The information included sociodemographic data, booking status, complications in pregnancy, estimated gestational age, placental weight, FW, foetal outcome and Apgar scores at 1 and 5 min.
The data obtained were analysed using SPSS version 20 (IBM Corp., USA). Mean values of parameters are presented with values of standard deviation. Groupings of gestational age at delivery were presented as frequency and percentages. Histograms were drawn and distribution curves were constructed to assess normality/distribution of data. Chi-square (χ2) test and Student's t-test were used to test for association where applicable. Fisher's exact test was used where value in a cell is <5 and Chi-square was not applicable. Spearman's rank correlation was used to assess the correlation between gestational age and FW, PW and F/P ratio. P < 0.05 was considered to be statistically significant. Percentiles values were calculated for the mean values of FW, PW and F/P ratio at various gestational ages, and sex-specific nomograms were constructed for specific parameters. Missing data were excluded from the analysis.
| Results|| |
Clinical profile of patients
A total of 2678 women delivered during the study period. Of these, 1804 were included in this study based on the selection criteria. The mean age ± standard error of mean of the parturients was 31.84 ± 0.18 years. They were predominantly booked patients comprising 1455 (80.7%), whereas the unbooked patients were 348 (19.3% of the study population). They were mostly of low parity. Para 0–1 comprised 1066 (59.1%), Para 2–4 were 676 (37.5%) and Para 5 and above were 35 (1.9%). The mean gestational age ± standard deviation (SD) at delivery was 37.81 ± 2.72 weeks. Preterm deliveries, 28–36-week gestational age, comprised 297 (16.5%). Deliveries from 37 to 39 completed weeks comprised 1002 (55.5%). Post-date pregnancies between 40 and 41 completed weeks comprised 432 (23.9%). Prolonged pregnancies from 42 weeks gestational age and above comprised 22 (1.2%).
Test of normality of data
When normality curve was constructed using the age of parturients, the study population was found to be normally distributed. Using F/P weight ratio to construct a distribution curve, the study population was also found to be normally distributed. Using the gestational age at delivery, the distribution curve was negatively skewed.
Factors affecting foeto-placental parameters
We assessed the influence of maternal age, parity, booking status, gestational age and foetal sex on the F/P indices. We found that only gestational age and booking status significantly influence PW, FW and F/P ratio (P = 0.000 for all parameters). The unbooked mothers had lighter babies, with smaller placentae and lower F/P ratio. The unbooked and booked parturient had mean ± SD values of 2545 g ± 982 g and 3225 g ± 545 g, respectively, for FW, 664 g ± 495 g and 751 g ± 213 g, respectively for PW and 4.30 ± 2.29 and 4.61 ± 2.00, respectively, for F/P ratio. [Figure 1] shows the correlation between gestational age and F/P indices. Foetal weight is also significantly influenced by parity (P = 0.026) and foetal sex (P = 0.000). The mean FW is lower in women of low parity 0–1 compared to the multiparous 2–4 (3067 ± 704 g vs. 3149 ± 687 g, respectively) and much lower in the grandmultiparous ≥ 5 (3004 ± 905 g). The mean FW is higher for the male babies than that of the female babies (3153 ± 698 g vs. 3034 ± 700 g, respectively). Maternal age does not have any statistically significant influence on the three F/P indices studied.
|Figure 1: Correlation between foetal and placental indices and gestational age|
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Association between foetal and placental weight parameters and foetal outcome
The live births were significantly heavier with larger placenta than stillbirths, but this study did not find any statistically significant difference in their mean F/P weight ratio. [Table 1] shows the summary of this finding. Only foetal weight showed a statistically significant relationship with Apgar score at 1 min (P = 0.000), whereas both foetal weight and PW showed a statistically significant relationship with the Apgar score at 5 min (P = 0.000 for each parameter). [Table 2] shows the association between F/P indices and Apgar scores.
|Table 1: Association between foetal and placental weight parameters and foetal outcome|
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Correlation between foeto-placental indices and gestational age
There was a positive correlation between gestational age and FW (r = 0.481, P = 0.000), gestational age and PW (r = 0.239, P = 0.000) and gestational age and F/P ratio (r = 0.209, P = 0.000). There was a rapid increase in the F/P ratio when pregnancy gets to 42-week gestational age and a subsequent decrease after 43-week gestational age [Figure 1]. F/P ratio is lower in female foetuses than male foetuses, but this finding was not statistically significant (P = 0.448) [Figure 2]. [Table 3] shows percentile values of F/P ratio at various gestational ages, whereas [Figure 3]a and [Figure 3]b are normograms derived from these values.
|Figure 2: Relationship between foeto-placental weight ratio and foetal sex|
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|Table 3: Percentile values for fetoplacental weight ratio in the third trimester of normal pregnancy|
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|Figure 3: (a) Normogram for foeto-placental weight ratio in male foetuses. (b) Normogram for foeto-placental weight ratio in female foetuses|
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| Discussion|| |
This study found that there was a moderate positive correlation between gestational age and FW, and a weak positive correlation between gestational age and PW and between gestational age and F/P ratio. These correlations were, however, statistically significant. This is not an unusual finding as the foetus and the placenta grows progressively in pregnancy. We report here some remarkable findings in the differential growth rate pattern of the foetus and placenta as found in this study.
The placenta gains weight slowly in the third trimester of pregnancy with a slight decrease in the weight from 42-week gestational age possibly due to placental infarction, which is associated with prolonged pregnancy. The foetus gains weight more rapidly in the third trimester until 43-week gestational age, with an associated steep rise in the F/P ratio. Thereafter, foetal growth declines. This goes to show that at 42-week gestational age, the foetus outgrows its placenta, and the resultant effect is depletion in nutrient and oxygen supply, resulting in a slowing of the foetal growth further worsened by placental infarction. There is thus a need to avoid prolongation of pregnancy beyond 42 weeks even in women with uncomplicated pregnancies.
Apart from gestational age which is well known as a major factor influencing F/P indices, booking status was found to affect FW, PW and F/P ratio significantly (P = 0.000). The values of these parameters were found to be lower in unbooked women compared to booked women. This is probably so because the unbooked patients are often women of low socioeconomic status with poor nutritional status and who did not have formal antenatal care. They are at higher risk of complications such as anaemia and other complications of pregnancy, which may increase their risk of having growth-restricted babies.
Parity was found to have significant influence on FW only (P = 0.000), and the relationship remains the same as in earlier studies.,, Multiparous women have heavier babies than women of low parity 0–1, whereas the grandmultiparous babies are lighter than babies of nulliparous and primiparous women. The association between parity and birth weight has been linked to the higher incidence of complications in nulliparous and grandmultiparous women. Earlier studies have found an increase in the incidence low-birth weight babies and medical complications such as hypertension in nulliparous women and increased incidence of anaemia in grandmultiparous women.,
Foetal sex was also found to have a statistically significant influence on FW, male babies being 119 g heavier than female babies in this study (P = 0.000). This has been a recurrent finding in a number of studies and genetic predisposition and increased sensitivity to the intrauterine environment, and maternal glucose levels in female foetuses are thought to contribute. Although female foetuses were also found to have smaller F/P ratio than male foetuses, this study did not establish any statistically significant difference in the F/P ratio between both sexes (P = 0.448) as was reported in an earlier study by Matsuda et al.
| Conclusion|| |
The change in the pattern of foetal and placental growth in normal pregnancy may account for the increased risk of sudden foetal demise and other complications associated with prolonged pregnancy. A good understanding of the foetal and placental growth pattern is thus essential. This study clarified the need to avoid undue prolongation of pregnancy beyond 42 weeks to avert adverse consequences, which may be related to the differential growth in the foetus and placenta.
Financial support and sponsorship
The cost of the research was borne solely by the authors.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3]