Relationship between parity and the problems that appear in the postpartum period

Parity is associated with the incidence of problems in pregnancy, delivery and the puerperium. The influence of parity in the postpartum period has been poorly studied and the results are incongruous. The objective of this study was to identify the association between parity and the existence of distinct discomfort and problems during the postpartum period. Cross-sectional study with puerperal women in Spain. Data was collected on demographic and obstetric variables and maternal manifestations of discomfort and problems during the postpartum period. An ad hoc online questionnaire was used. Crude odds ratios (ORs) and adjusted odds ratios (aORs) with 95% confidence intervals (CIs) were estimated by conditional logistic regression. 1503 primiparous and 1487 multiparous participated in the study. 53.4% (803) of the primiparous women affirmed to have feelings of sadness, as opposed to 36.2% (539) of multiparous women (aOR: 1.60; 95% CI: 1.35–1.89). 48.3% (726) of primiparous had lactation problems vs 24.7% (367) of multiparous (aOR: 2.46; 95% CI: 2.05–2.94). 37.2% (559) of primiparous reported anxiety, while the percentage in multiparous was 25.7% (382) (aOR: 1.34; 95% CI: 1.12–1.61). 22.2% (333) of primiparous had depressive symptoms, and 11.6% (172) of multiparous (aOR: 1.65; CI 95%: 1.31–2.06). Faecal incontinence was more present in primiparous than in multiparous, 6.5% (97) and 3.3% (49) respectively (aOR: 1.60; 95% CI: 1.07–2.38). Parity is associated with the presence of certain problems in the postpartum period. Thus, primiparous are more likely to have lactation problems, depressive symptoms, anxiety, sadness, and faecal incontinence.

Furthermore, 36.7% (552) of primiparous mothers' children received artificial feeding at hospital discharge, while for multiparous mothers' children, this percentage was 21.9% (326) (OR: 2.07; CI 95%: 1.76-2.43). In Table 1, the other characteristics of the study sample and the factors associated with parity can be seen. Table 2 shows the association between different puerperal discomforts and complications and parity. The reference category was multiparity, so the calculated Odds Ratios represent the probability of primiparous of suffering problems/discomfort as compared to multiparous. In this

Discussion
Our results identified an association between parity and various problems and discomforts that women suffer during the puerperium. Primiparous women, as compared to multiparous, are less likely to have haemorrhoids and headaches. However, they have an increased risk of having lactation complications, sexual problems, problems in the habitual dynamics of the couple, faecal incontinence, burning during urination, perineal pain, breast pain, depression, anxiety, and sadness symptoms.
Among the factors associated with parity, from our results one can get that age ≥35 years was associated with being multiparous. This may be due to the fact that being older increases the chances of having had a previous pregnancy. Likewise, women who perform more skin-to-skin contact with their newborn are also multiparous compared to primiparous. In this same line, in a Swedish study on 64 newborns, 54.7% of the multiparous kept early skin-to-skin contact compared to 45.3% of the primiparous 14 . Other clinical variables and practices such as artificial feeding at discharge, the realization of an episiotomy, which produces a severe perineal tearing of III or IV degree during the delivery, the use of epidural, having a dystocia, the onset of a delivery in a non-spontaneous way, attending childbirth classes during pregnancy, and having a multiple pregnancy were positively associated with primiparity, in line with what is established in most scientific literature 9,13,[15][16][17][18][19][20] .
Being multiparous is a risk factor for having haemorrhoids during the puerperium, in the line of what Jong-Hyun et al. detected in a study in Korea 21 and Poskus et al. in a study with 280 women a month after childbirth conducted in Lithuania 22 . Also, multiparity was associated with greater headaches in the puerperium, as Sharff et al. already stated 23 .
Women who have their first birth presented more frequent perineal pain in the puerperium, also in line with the results of other authors 22 . Also, women who were in their first birth showed a greater presence of depressive, anxious and sad feelings, and they also rekindled the delivery upsettingly. All these feelings can be due to cortisol levels, very mood-related. Gillespie et al. detected an interaction between parity and cortisol levels 24 . However, Hartmann et al. 25 , in the opposite direction of our results, identified the association between multiparity and postpartum depression.
On the other hand, the primiparous showed more sexual problems in the puerperium than the multiparous. In this sense, the results of the study by Yee et al. 26 , carried out on 160 postpartum women, show an earlier retake of sexual relations and with greater satisfaction in the multiparous, in the same line with our results.
Discomfort and burning when urinating, breast pain and faecal incontinence were more frequently in primiparous women.
Prinds et al. 27 , in a survey on 499 women in Denmark, concluded that the first child birth had forged stronger ties between couples, as opposed to the results of our study. Although the results of Mchale & Huston 28 show that the transition to paternity affects fellowship and marital role patterns, no evidence was found to support the idea that paternity is associated with a decrease in mutual assessments (love) or marriage assessment (marital satisfaction).
Regarding lactation, primiparous women had a higher risk of having problems than multiparous, perhaps due to the experience acquired with previous children. Our results go in line with other authors 9,29-31 .
In the case of a non-response selection bias, it has had no influence on the results. Women's response to the participation has been preponderant. Only 29 refused to participate (13 multiparous, 0.82% of all multiparous, and 16 primiparous, 0.92% of the primiparous participants) and nothing suggests that those who did not respond would have done so differently from those that did. Likewise, both in the multiparous and primiparous groups, the rejection to participate was similar: 0.82% vs 0.92%. The existence of an information bias is unlikely: the data collected, as well as the way in which the possible responses were posed, do not require a high level of education. The questions were presented in a basic and simple, affordable and comprehensible way for any educational level. It is not completely possible to reject a recall bias, although the information was collected in a short interval of www.nature.com/scientificreports www.nature.com/scientificreports/ time. Therefore, if there was an influence on the results, we believe it would have been minimal. Women especially remember the information on their birth process, which is generally highly valued and deserves special attention on their part. It is not possible to ignore a residual confusion bias, even if the influence on the results would have been minimal, since the adjustment of each variable has been carried out in an individualised and specific way through those variables that have possibly influenced this specific one.
Among the strengths of the study, we must highlight that the sample size is large, with women from different geographical areas, so it includes all the possible sensitivities of the reference population.

conclusion
In conclusion, parity is associated with the type of discomfort and problems that women have in the puerperium. Primiparous women show more symptoms related to mental health such as anxiety, depression and sadness, as well as couple dynamics and sexuality problems, among others. The multiparous women presented a greater frequency of haemorrhoids and headaches in the postpartum period.

Methods
A cross-sectional study was conducted with women who gave birth in Spain in 2017 (both in public health system centres and private centres). Births with antepartum stillbirths and women under 18 years of age were excluded.
For the sample size estimation, the criterion of maximum modelling was considered 32 . This implied including 10 events (complications) for each independent variable that was to be incorporated in the multivariate analysis. Considering faecal incontinence 33 as the less frequent complication (4%), a minimum of 2500 women were required to incorporate a minimum of 10 independent variables (100 × 100/4 = 2500).

Sources of information. For the data collection, a self-elaborated online questionnaire of 35 items (3 open
questions and 32 closed questions) was given to the women 6 weeks after the delivery. Data was collected on sociodemographic and clinical characteristics, obstetric outcomes, newborns data and complications, discomfort and needs of postpartum women. The questionnaire was piloted by the researchers and midwives who would recruit the participants for the study. It was piloted with women from different Spanish geographical areas, with different levels of studies and ages. The Associations of Spanish Midwives Federation (FAME, for its acronym in Spanish), as well as their member associations, were involved in the dissemination of the project and in the recruitment of participants. These involved their midwives in the dissemination of project and in the recruitment of participants. These midwives helped in the recruitment of women and were also trained to explain and support women in completing the questionnaire if necessary. Once the study subjects were selected and they had agreed to participate, they were given the instructions to complete the questionnaire (self-administered), which they filled according to their availability. There was a telephone number and a chat destined to answer all the possible questions these women may have had in completing the questionnaire.
The following variables were collected. The main outcomes were women symptoms of: constipation problems, presence of haemorrhoids, wound infection (need of professional cures after discharge from hospital and/or consumption of antibiotics, perineal pain, headache, breast pain, back pain, pains or burning sensation during urination, faecal incontinence (inability to control bowel movements), urinary incontinence (involuntary urine loss), tiredness, sadness, anxiety (nervousness and/or restlessness), depression (depressive mood), problems related to maintaining sexual intercourse, problems in couple's relationship dynamics after birth, and problems related to lactation. All the dependent variables were dichotomous (yes/no).
Statistical analysis employed. The main independent variable was parity (Primiparous: a woman in her first birth; Multiparous: a woman in her second or further birth).
The variables considered for the confounding control were of demographic (maternal age, academic level, maternal training, nationality) and clinical type (type of delivery: type of birth: being eutocic, instrumental, or performing a caesarean), multiple birth (childbirth with more than one newborn), complications during pregnancy (appearance of haemorrhages, fever, need for surgical intervention after delivery, among others), induced birth (labour that does not start spontaneously, medicines are used to start it), epidural use/spinal anesthesia (analgesia that is administered through the epidural space), episiotomy (surgical incision that is made in the perineum to facilitate the expulsion of the foetus), severe perineal tearing (spontaneous lesion of the perineal that occurs during the expulsion of the foetus, tears of III or IV degree that affect the integrity of the anal sphincter), gestational age (week of pregnancy at which labour occurs), skin-to-skin (recommended clinical practice consisting of establishing direct contact between the newborn and the mother: skin to skin), newborn admittance (need for hospital admission of the newborn), and type of lactation (type of lactation with which the newborn is fed: exclusively breastfeeding, mixed lactation, or exclusively with artificial formulas), using in each case the specific variables that could potentially act as confusing for each specific result, that is, individualising the adjustment variables for each result.
Firstly, a descriptive analysis was carried out with absolute and relative frequencies. Then, a bivariate analysis was carried out between parity and the main manifestations/complications/discomforts that women showed through binary logistic regression. Later, a multivariate analysis was carried out through logistic regression, using SPSS forward and backward selection. The aim of this analysis was to determine the net effect of parity on each postpartum problem/type of discomfort. For each analysis, the potentially confounding variables were included, following clinical criteria.
Crude odds ratios (cOR) and adjusted odds ratios (aOR) and their confidence intervals (CI) were calculated at 95%.
A p < 0.05 was considered as significant. All analyses were carried out with the SPSS v24.0 statistical package. Spanish acronym) of the La Mancha-Centro Centre with ethical code 69-C. Before starting the questionnaire, the participating women read a fact sheet about the study, its objectives, etc., and marked a box by which they showed their consent to participate in it, i.e., they signed an online informed consent (ticking the option if they wanted to participate or not doing so when refusing to take part in the study). The protocols established to carry out this type of research were followed with the purpose of publication/disclosure to the scientific community. The study was conducted according to the guidelines set in the Declaration of Helsinki and all procedures involving human subjects were approved by the Ethics Committee. All women involved in this study filled out an informed consent and data treatment forms to enter the study, in accordance with the ethical standards of the Ethics Committee.